Skip to content
Snippets Groups Projects
Select Git revision
  • dabe19540af9e563d526113bb102e1b9b9fa73f9
  • vme-testing default
  • ci-test
  • master
  • remoteproc
  • am625-sk-ov5640
  • pcal6534-upstreaming
  • lps22df-upstreaming
  • msc-upstreaming
  • imx8mp
  • iio/noa1305
  • vme-next
  • vme-next-4.14-rc4
  • v4.14-rc4
  • v4.14-rc3
  • v4.14-rc2
  • v4.14-rc1
  • v4.13
  • vme-next-4.13-rc7
  • v4.13-rc7
  • v4.13-rc6
  • v4.13-rc5
  • v4.13-rc4
  • v4.13-rc3
  • v4.13-rc2
  • v4.13-rc1
  • v4.12
  • v4.12-rc7
  • v4.12-rc6
  • v4.12-rc5
  • v4.12-rc4
  • v4.12-rc3
32 results

drm_dp_mst_topology.c

Blame
  • drm_dp_mst_topology.c 80.50 KiB
    /*
     * Copyright © 2014 Red Hat
     *
     * Permission to use, copy, modify, distribute, and sell this software and its
     * documentation for any purpose is hereby granted without fee, provided that
     * the above copyright notice appear in all copies and that both that copyright
     * notice and this permission notice appear in supporting documentation, and
     * that the name of the copyright holders not be used in advertising or
     * publicity pertaining to distribution of the software without specific,
     * written prior permission.  The copyright holders make no representations
     * about the suitability of this software for any purpose.  It is provided "as
     * is" without express or implied warranty.
     *
     * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
     * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
     * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
     * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
     * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
     * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
     * OF THIS SOFTWARE.
     */
    
    #include <linux/kernel.h>
    #include <linux/delay.h>
    #include <linux/init.h>
    #include <linux/errno.h>
    #include <linux/sched.h>
    #include <linux/seq_file.h>
    #include <linux/i2c.h>
    #include <drm/drm_dp_mst_helper.h>
    #include <drm/drmP.h>
    
    #include <drm/drm_fixed.h>
    
    /**
     * DOC: dp mst helper
     *
     * These functions contain parts of the DisplayPort 1.2a MultiStream Transport
     * protocol. The helpers contain a topology manager and bandwidth manager.
     * The helpers encapsulate the sending and received of sideband msgs.
     */
    static bool dump_dp_payload_table(struct drm_dp_mst_topology_mgr *mgr,
    				  char *buf);
    static int test_calc_pbn_mode(void);
    
    static void drm_dp_put_port(struct drm_dp_mst_port *port);
    
    static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr,
    				     int id,
    				     struct drm_dp_payload *payload);
    
    static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
    				  struct drm_dp_mst_port *port,
    				  int offset, int size, u8 *bytes);
    
    static void drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
    				     struct drm_dp_mst_branch *mstb);
    static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
    					   struct drm_dp_mst_branch *mstb,
    					   struct drm_dp_mst_port *port);
    static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
    				 u8 *guid);
    
    static int drm_dp_mst_register_i2c_bus(struct drm_dp_aux *aux);
    static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_aux *aux);
    static void drm_dp_mst_kick_tx(struct drm_dp_mst_topology_mgr *mgr);
    /* sideband msg handling */
    static u8 drm_dp_msg_header_crc4(const uint8_t *data, size_t num_nibbles)
    {
    	u8 bitmask = 0x80;
    	u8 bitshift = 7;
    	u8 array_index = 0;
    	int number_of_bits = num_nibbles * 4;
    	u8 remainder = 0;
    
    	while (number_of_bits != 0) {
    		number_of_bits--;
    		remainder <<= 1;
    		remainder |= (data[array_index] & bitmask) >> bitshift;
    		bitmask >>= 1;
    		bitshift--;
    		if (bitmask == 0) {
    			bitmask = 0x80;
    			bitshift = 7;
    			array_index++;
    		}
    		if ((remainder & 0x10) == 0x10)
    			remainder ^= 0x13;
    	}
    
    	number_of_bits = 4;
    	while (number_of_bits != 0) {
    		number_of_bits--;
    		remainder <<= 1;
    		if ((remainder & 0x10) != 0)
    			remainder ^= 0x13;
    	}
    
    	return remainder;
    }
    
    static u8 drm_dp_msg_data_crc4(const uint8_t *data, u8 number_of_bytes)
    {
    	u8 bitmask = 0x80;
    	u8 bitshift = 7;
    	u8 array_index = 0;
    	int number_of_bits = number_of_bytes * 8;
    	u16 remainder = 0;
    
    	while (number_of_bits != 0) {
    		number_of_bits--;
    		remainder <<= 1;
    		remainder |= (data[array_index] & bitmask) >> bitshift;
    		bitmask >>= 1;
    		bitshift--;
    		if (bitmask == 0) {
    			bitmask = 0x80;
    			bitshift = 7;
    			array_index++;
    		}
    		if ((remainder & 0x100) == 0x100)
    			remainder ^= 0xd5;
    	}
    
    	number_of_bits = 8;
    	while (number_of_bits != 0) {
    		number_of_bits--;
    		remainder <<= 1;
    		if ((remainder & 0x100) != 0)
    			remainder ^= 0xd5;
    	}
    
    	return remainder & 0xff;
    }
    static inline u8 drm_dp_calc_sb_hdr_size(struct drm_dp_sideband_msg_hdr *hdr)
    {
    	u8 size = 3;
    	size += (hdr->lct / 2);
    	return size;
    }
    
    static void drm_dp_encode_sideband_msg_hdr(struct drm_dp_sideband_msg_hdr *hdr,
    					   u8 *buf, int *len)
    {
    	int idx = 0;
    	int i;
    	u8 crc4;
    	buf[idx++] = ((hdr->lct & 0xf) << 4) | (hdr->lcr & 0xf);
    	for (i = 0; i < (hdr->lct / 2); i++)
    		buf[idx++] = hdr->rad[i];
    	buf[idx++] = (hdr->broadcast << 7) | (hdr->path_msg << 6) |
    		(hdr->msg_len & 0x3f);
    	buf[idx++] = (hdr->somt << 7) | (hdr->eomt << 6) | (hdr->seqno << 4);
    
    	crc4 = drm_dp_msg_header_crc4(buf, (idx * 2) - 1);
    	buf[idx - 1] |= (crc4 & 0xf);
    
    	*len = idx;
    }
    
    static bool drm_dp_decode_sideband_msg_hdr(struct drm_dp_sideband_msg_hdr *hdr,
    					   u8 *buf, int buflen, u8 *hdrlen)
    {
    	u8 crc4;
    	u8 len;
    	int i;
    	u8 idx;
    	if (buf[0] == 0)
    		return false;
    	len = 3;
    	len += ((buf[0] & 0xf0) >> 4) / 2;
    	if (len > buflen)
    		return false;
    	crc4 = drm_dp_msg_header_crc4(buf, (len * 2) - 1);
    
    	if ((crc4 & 0xf) != (buf[len - 1] & 0xf)) {
    		DRM_DEBUG_KMS("crc4 mismatch 0x%x 0x%x\n", crc4, buf[len - 1]);
    		return false;
    	}
    
    	hdr->lct = (buf[0] & 0xf0) >> 4;
    	hdr->lcr = (buf[0] & 0xf);
    	idx = 1;
    	for (i = 0; i < (hdr->lct / 2); i++)
    		hdr->rad[i] = buf[idx++];
    	hdr->broadcast = (buf[idx] >> 7) & 0x1;
    	hdr->path_msg = (buf[idx] >> 6) & 0x1;
    	hdr->msg_len = buf[idx] & 0x3f;
    	idx++;
    	hdr->somt = (buf[idx] >> 7) & 0x1;
    	hdr->eomt = (buf[idx] >> 6) & 0x1;
    	hdr->seqno = (buf[idx] >> 4) & 0x1;
    	idx++;
    	*hdrlen = idx;
    	return true;
    }
    
    static void drm_dp_encode_sideband_req(struct drm_dp_sideband_msg_req_body *req,
    				       struct drm_dp_sideband_msg_tx *raw)
    {
    	int idx = 0;
    	int i;
    	u8 *buf = raw->msg;
    	buf[idx++] = req->req_type & 0x7f;
    
    	switch (req->req_type) {
    	case DP_ENUM_PATH_RESOURCES:
    		buf[idx] = (req->u.port_num.port_number & 0xf) << 4;
    		idx++;
    		break;
    	case DP_ALLOCATE_PAYLOAD:
    		buf[idx] = (req->u.allocate_payload.port_number & 0xf) << 4 |
    			(req->u.allocate_payload.number_sdp_streams & 0xf);
    		idx++;
    		buf[idx] = (req->u.allocate_payload.vcpi & 0x7f);
    		idx++;
    		buf[idx] = (req->u.allocate_payload.pbn >> 8);
    		idx++;
    		buf[idx] = (req->u.allocate_payload.pbn & 0xff);
    		idx++;
    		for (i = 0; i < req->u.allocate_payload.number_sdp_streams / 2; i++) {
    			buf[idx] = ((req->u.allocate_payload.sdp_stream_sink[i * 2] & 0xf) << 4) |
    				(req->u.allocate_payload.sdp_stream_sink[i * 2 + 1] & 0xf);
    			idx++;
    		}
    		if (req->u.allocate_payload.number_sdp_streams & 1) {
    			i = req->u.allocate_payload.number_sdp_streams - 1;
    			buf[idx] = (req->u.allocate_payload.sdp_stream_sink[i] & 0xf) << 4;
    			idx++;
    		}
    		break;
    	case DP_QUERY_PAYLOAD:
    		buf[idx] = (req->u.query_payload.port_number & 0xf) << 4;
    		idx++;
    		buf[idx] = (req->u.query_payload.vcpi & 0x7f);
    		idx++;
    		break;
    	case DP_REMOTE_DPCD_READ:
    		buf[idx] = (req->u.dpcd_read.port_number & 0xf) << 4;
    		buf[idx] |= ((req->u.dpcd_read.dpcd_address & 0xf0000) >> 16) & 0xf;
    		idx++;
    		buf[idx] = (req->u.dpcd_read.dpcd_address & 0xff00) >> 8;
    		idx++;
    		buf[idx] = (req->u.dpcd_read.dpcd_address & 0xff);
    		idx++;
    		buf[idx] = (req->u.dpcd_read.num_bytes);
    		idx++;
    		break;
    
    	case DP_REMOTE_DPCD_WRITE:
    		buf[idx] = (req->u.dpcd_write.port_number & 0xf) << 4;
    		buf[idx] |= ((req->u.dpcd_write.dpcd_address & 0xf0000) >> 16) & 0xf;
    		idx++;
    		buf[idx] = (req->u.dpcd_write.dpcd_address & 0xff00) >> 8;
    		idx++;
    		buf[idx] = (req->u.dpcd_write.dpcd_address & 0xff);
    		idx++;
    		buf[idx] = (req->u.dpcd_write.num_bytes);
    		idx++;
    		memcpy(&buf[idx], req->u.dpcd_write.bytes, req->u.dpcd_write.num_bytes);
    		idx += req->u.dpcd_write.num_bytes;
    		break;
    	case DP_REMOTE_I2C_READ:
    		buf[idx] = (req->u.i2c_read.port_number & 0xf) << 4;
    		buf[idx] |= (req->u.i2c_read.num_transactions & 0x3);
    		idx++;
    		for (i = 0; i < (req->u.i2c_read.num_transactions & 0x3); i++) {
    			buf[idx] = req->u.i2c_read.transactions[i].i2c_dev_id & 0x7f;
    			idx++;
    			buf[idx] = req->u.i2c_read.transactions[i].num_bytes;
    			idx++;
    			memcpy(&buf[idx], req->u.i2c_read.transactions[i].bytes, req->u.i2c_read.transactions[i].num_bytes);
    			idx += req->u.i2c_read.transactions[i].num_bytes;
    
    			buf[idx] = (req->u.i2c_read.transactions[i].no_stop_bit & 0x1) << 5;
    			buf[idx] |= (req->u.i2c_read.transactions[i].i2c_transaction_delay & 0xf);
    			idx++;
    		}
    		buf[idx] = (req->u.i2c_read.read_i2c_device_id) & 0x7f;
    		idx++;
    		buf[idx] = (req->u.i2c_read.num_bytes_read);
    		idx++;
    		break;
    
    	case DP_REMOTE_I2C_WRITE:
    		buf[idx] = (req->u.i2c_write.port_number & 0xf) << 4;
    		idx++;
    		buf[idx] = (req->u.i2c_write.write_i2c_device_id) & 0x7f;
    		idx++;
    		buf[idx] = (req->u.i2c_write.num_bytes);
    		idx++;
    		memcpy(&buf[idx], req->u.i2c_write.bytes, req->u.i2c_write.num_bytes);
    		idx += req->u.i2c_write.num_bytes;
    		break;
    	}
    	raw->cur_len = idx;
    }
    
    static void drm_dp_crc_sideband_chunk_req(u8 *msg, u8 len)
    {
    	u8 crc4;
    	crc4 = drm_dp_msg_data_crc4(msg, len);
    	msg[len] = crc4;
    }
    
    static void drm_dp_encode_sideband_reply(struct drm_dp_sideband_msg_reply_body *rep,
    					 struct drm_dp_sideband_msg_tx *raw)
    {
    	int idx = 0;
    	u8 *buf = raw->msg;
    
    	buf[idx++] = (rep->reply_type & 0x1) << 7 | (rep->req_type & 0x7f);
    
    	raw->cur_len = idx;
    }
    
    /* this adds a chunk of msg to the builder to get the final msg */
    static bool drm_dp_sideband_msg_build(struct drm_dp_sideband_msg_rx *msg,
    				      u8 *replybuf, u8 replybuflen, bool hdr)
    {
    	int ret;
    	u8 crc4;
    
    	if (hdr) {
    		u8 hdrlen;
    		struct drm_dp_sideband_msg_hdr recv_hdr;
    		ret = drm_dp_decode_sideband_msg_hdr(&recv_hdr, replybuf, replybuflen, &hdrlen);
    		if (ret == false) {
    			print_hex_dump(KERN_DEBUG, "failed hdr", DUMP_PREFIX_NONE, 16, 1, replybuf, replybuflen, false);
    			return false;
    		}
    
    		/* get length contained in this portion */
    		msg->curchunk_len = recv_hdr.msg_len;
    		msg->curchunk_hdrlen = hdrlen;
    
    		/* we have already gotten an somt - don't bother parsing */
    		if (recv_hdr.somt && msg->have_somt)
    			return false;
    
    		if (recv_hdr.somt) {
    			memcpy(&msg->initial_hdr, &recv_hdr, sizeof(struct drm_dp_sideband_msg_hdr));
    			msg->have_somt = true;
    		}
    		if (recv_hdr.eomt)
    			msg->have_eomt = true;
    
    		/* copy the bytes for the remainder of this header chunk */
    		msg->curchunk_idx = min(msg->curchunk_len, (u8)(replybuflen - hdrlen));
    		memcpy(&msg->chunk[0], replybuf + hdrlen, msg->curchunk_idx);
    	} else {
    		memcpy(&msg->chunk[msg->curchunk_idx], replybuf, replybuflen);
    		msg->curchunk_idx += replybuflen;
    	}
    
    	if (msg->curchunk_idx >= msg->curchunk_len) {
    		/* do CRC */
    		crc4 = drm_dp_msg_data_crc4(msg->chunk, msg->curchunk_len - 1);
    		/* copy chunk into bigger msg */
    		memcpy(&msg->msg[msg->curlen], msg->chunk, msg->curchunk_len - 1);
    		msg->curlen += msg->curchunk_len - 1;
    	}
    	return true;
    }
    
    static bool drm_dp_sideband_parse_link_address(struct drm_dp_sideband_msg_rx *raw,
    					       struct drm_dp_sideband_msg_reply_body *repmsg)
    {
    	int idx = 1;
    	int i;
    	memcpy(repmsg->u.link_addr.guid, &raw->msg[idx], 16);
    	idx += 16;
    	repmsg->u.link_addr.nports = raw->msg[idx] & 0xf;
    	idx++;
    	if (idx > raw->curlen)
    		goto fail_len;
    	for (i = 0; i < repmsg->u.link_addr.nports; i++) {
    		if (raw->msg[idx] & 0x80)
    			repmsg->u.link_addr.ports[i].input_port = 1;
    
    		repmsg->u.link_addr.ports[i].peer_device_type = (raw->msg[idx] >> 4) & 0x7;
    		repmsg->u.link_addr.ports[i].port_number = (raw->msg[idx] & 0xf);
    
    		idx++;
    		if (idx > raw->curlen)
    			goto fail_len;
    		repmsg->u.link_addr.ports[i].mcs = (raw->msg[idx] >> 7) & 0x1;
    		repmsg->u.link_addr.ports[i].ddps = (raw->msg[idx] >> 6) & 0x1;
    		if (repmsg->u.link_addr.ports[i].input_port == 0)
    			repmsg->u.link_addr.ports[i].legacy_device_plug_status = (raw->msg[idx] >> 5) & 0x1;
    		idx++;
    		if (idx > raw->curlen)
    			goto fail_len;
    		if (repmsg->u.link_addr.ports[i].input_port == 0) {
    			repmsg->u.link_addr.ports[i].dpcd_revision = (raw->msg[idx]);
    			idx++;
    			if (idx > raw->curlen)
    				goto fail_len;
    			memcpy(repmsg->u.link_addr.ports[i].peer_guid, &raw->msg[idx], 16);
    			idx += 16;
    			if (idx > raw->curlen)
    				goto fail_len;
    			repmsg->u.link_addr.ports[i].num_sdp_streams = (raw->msg[idx] >> 4) & 0xf;
    			repmsg->u.link_addr.ports[i].num_sdp_stream_sinks = (raw->msg[idx] & 0xf);
    			idx++;
    
    		}
    		if (idx > raw->curlen)
    			goto fail_len;
    	}
    
    	return true;
    fail_len:
    	DRM_DEBUG_KMS("link address reply parse length fail %d %d\n", idx, raw->curlen);
    	return false;
    }
    
    static bool drm_dp_sideband_parse_remote_dpcd_read(struct drm_dp_sideband_msg_rx *raw,
    						   struct drm_dp_sideband_msg_reply_body *repmsg)
    {
    	int idx = 1;
    	repmsg->u.remote_dpcd_read_ack.port_number = raw->msg[idx] & 0xf;
    	idx++;
    	if (idx > raw->curlen)
    		goto fail_len;
    	repmsg->u.remote_dpcd_read_ack.num_bytes = raw->msg[idx];
    	if (idx > raw->curlen)
    		goto fail_len;
    
    	memcpy(repmsg->u.remote_dpcd_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_dpcd_read_ack.num_bytes);
    	return true;
    fail_len:
    	DRM_DEBUG_KMS("link address reply parse length fail %d %d\n", idx, raw->curlen);
    	return false;
    }
    
    static bool drm_dp_sideband_parse_remote_dpcd_write(struct drm_dp_sideband_msg_rx *raw,
    						      struct drm_dp_sideband_msg_reply_body *repmsg)
    {
    	int idx = 1;
    	repmsg->u.remote_dpcd_write_ack.port_number = raw->msg[idx] & 0xf;
    	idx++;
    	if (idx > raw->curlen)
    		goto fail_len;
    	return true;
    fail_len:
    	DRM_DEBUG_KMS("parse length fail %d %d\n", idx, raw->curlen);
    	return false;
    }
    
    static bool drm_dp_sideband_parse_remote_i2c_read_ack(struct drm_dp_sideband_msg_rx *raw,
    						      struct drm_dp_sideband_msg_reply_body *repmsg)
    {
    	int idx = 1;
    
    	repmsg->u.remote_i2c_read_ack.port_number = (raw->msg[idx] & 0xf);
    	idx++;
    	if (idx > raw->curlen)
    		goto fail_len;
    	repmsg->u.remote_i2c_read_ack.num_bytes = raw->msg[idx];
    	idx++;
    	/* TODO check */
    	memcpy(repmsg->u.remote_i2c_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_i2c_read_ack.num_bytes);
    	return true;
    fail_len:
    	DRM_DEBUG_KMS("remote i2c reply parse length fail %d %d\n", idx, raw->curlen);
    	return false;
    }
    
    static bool drm_dp_sideband_parse_enum_path_resources_ack(struct drm_dp_sideband_msg_rx *raw,
    							  struct drm_dp_sideband_msg_reply_body *repmsg)
    {
    	int idx = 1;
    	repmsg->u.path_resources.port_number = (raw->msg[idx] >> 4) & 0xf;
    	idx++;
    	if (idx > raw->curlen)
    		goto fail_len;
    	repmsg->u.path_resources.full_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
    	idx += 2;
    	if (idx > raw->curlen)
    		goto fail_len;
    	repmsg->u.path_resources.avail_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
    	idx += 2;
    	if (idx > raw->curlen)
    		goto fail_len;
    	return true;
    fail_len:
    	DRM_DEBUG_KMS("enum resource parse length fail %d %d\n", idx, raw->curlen);
    	return false;
    }
    
    static bool drm_dp_sideband_parse_allocate_payload_ack(struct drm_dp_sideband_msg_rx *raw,
    							  struct drm_dp_sideband_msg_reply_body *repmsg)
    {
    	int idx = 1;
    	repmsg->u.allocate_payload.port_number = (raw->msg[idx] >> 4) & 0xf;
    	idx++;
    	if (idx > raw->curlen)
    		goto fail_len;
    	repmsg->u.allocate_payload.vcpi = raw->msg[idx];
    	idx++;
    	if (idx > raw->curlen)
    		goto fail_len;
    	repmsg->u.allocate_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
    	idx += 2;
    	if (idx > raw->curlen)
    		goto fail_len;
    	return true;
    fail_len:
    	DRM_DEBUG_KMS("allocate payload parse length fail %d %d\n", idx, raw->curlen);
    	return false;
    }
    
    static bool drm_dp_sideband_parse_query_payload_ack(struct drm_dp_sideband_msg_rx *raw,
    						    struct drm_dp_sideband_msg_reply_body *repmsg)
    {
    	int idx = 1;
    	repmsg->u.query_payload.port_number = (raw->msg[idx] >> 4) & 0xf;
    	idx++;
    	if (idx > raw->curlen)
    		goto fail_len;
    	repmsg->u.query_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx + 1]);
    	idx += 2;
    	if (idx > raw->curlen)
    		goto fail_len;
    	return true;
    fail_len:
    	DRM_DEBUG_KMS("query payload parse length fail %d %d\n", idx, raw->curlen);
    	return false;
    }
    
    static bool drm_dp_sideband_parse_reply(struct drm_dp_sideband_msg_rx *raw,
    					struct drm_dp_sideband_msg_reply_body *msg)
    {
    	memset(msg, 0, sizeof(*msg));
    	msg->reply_type = (raw->msg[0] & 0x80) >> 7;
    	msg->req_type = (raw->msg[0] & 0x7f);
    
    	if (msg->reply_type) {
    		memcpy(msg->u.nak.guid, &raw->msg[1], 16);
    		msg->u.nak.reason = raw->msg[17];
    		msg->u.nak.nak_data = raw->msg[18];
    		return false;
    	}
    
    	switch (msg->req_type) {
    	case DP_LINK_ADDRESS:
    		return drm_dp_sideband_parse_link_address(raw, msg);
    	case DP_QUERY_PAYLOAD:
    		return drm_dp_sideband_parse_query_payload_ack(raw, msg);
    	case DP_REMOTE_DPCD_READ:
    		return drm_dp_sideband_parse_remote_dpcd_read(raw, msg);
    	case DP_REMOTE_DPCD_WRITE:
    		return drm_dp_sideband_parse_remote_dpcd_write(raw, msg);
    	case DP_REMOTE_I2C_READ:
    		return drm_dp_sideband_parse_remote_i2c_read_ack(raw, msg);
    	case DP_ENUM_PATH_RESOURCES:
    		return drm_dp_sideband_parse_enum_path_resources_ack(raw, msg);
    	case DP_ALLOCATE_PAYLOAD:
    		return drm_dp_sideband_parse_allocate_payload_ack(raw, msg);
    	default:
    		DRM_ERROR("Got unknown reply 0x%02x\n", msg->req_type);
    		return false;
    	}
    }
    
    static bool drm_dp_sideband_parse_connection_status_notify(struct drm_dp_sideband_msg_rx *raw,
    							   struct drm_dp_sideband_msg_req_body *msg)
    {
    	int idx = 1;
    
    	msg->u.conn_stat.port_number = (raw->msg[idx] & 0xf0) >> 4;
    	idx++;
    	if (idx > raw->curlen)
    		goto fail_len;
    
    	memcpy(msg->u.conn_stat.guid, &raw->msg[idx], 16);
    	idx += 16;
    	if (idx > raw->curlen)
    		goto fail_len;
    
    	msg->u.conn_stat.legacy_device_plug_status = (raw->msg[idx] >> 6) & 0x1;
    	msg->u.conn_stat.displayport_device_plug_status = (raw->msg[idx] >> 5) & 0x1;
    	msg->u.conn_stat.message_capability_status = (raw->msg[idx] >> 4) & 0x1;
    	msg->u.conn_stat.input_port = (raw->msg[idx] >> 3) & 0x1;
    	msg->u.conn_stat.peer_device_type = (raw->msg[idx] & 0x7);
    	idx++;
    	return true;
    fail_len:
    	DRM_DEBUG_KMS("connection status reply parse length fail %d %d\n", idx, raw->curlen);
    	return false;
    }
    
    static bool drm_dp_sideband_parse_resource_status_notify(struct drm_dp_sideband_msg_rx *raw,
    							   struct drm_dp_sideband_msg_req_body *msg)
    {
    	int idx = 1;
    
    	msg->u.resource_stat.port_number = (raw->msg[idx] & 0xf0) >> 4;
    	idx++;
    	if (idx > raw->curlen)
    		goto fail_len;
    
    	memcpy(msg->u.resource_stat.guid, &raw->msg[idx], 16);
    	idx += 16;
    	if (idx > raw->curlen)
    		goto fail_len;
    
    	msg->u.resource_stat.available_pbn = (raw->msg[idx] << 8) | (raw->msg[idx + 1]);
    	idx++;
    	return true;
    fail_len:
    	DRM_DEBUG_KMS("resource status reply parse length fail %d %d\n", idx, raw->curlen);
    	return false;
    }
    
    static bool drm_dp_sideband_parse_req(struct drm_dp_sideband_msg_rx *raw,
    				      struct drm_dp_sideband_msg_req_body *msg)
    {
    	memset(msg, 0, sizeof(*msg));
    	msg->req_type = (raw->msg[0] & 0x7f);
    
    	switch (msg->req_type) {
    	case DP_CONNECTION_STATUS_NOTIFY:
    		return drm_dp_sideband_parse_connection_status_notify(raw, msg);
    	case DP_RESOURCE_STATUS_NOTIFY:
    		return drm_dp_sideband_parse_resource_status_notify(raw, msg);
    	default:
    		DRM_ERROR("Got unknown request 0x%02x\n", msg->req_type);
    		return false;
    	}
    }
    
    static int build_dpcd_write(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32 offset, u8 num_bytes, u8 *bytes)
    {
    	struct drm_dp_sideband_msg_req_body req;
    
    	req.req_type = DP_REMOTE_DPCD_WRITE;
    	req.u.dpcd_write.port_number = port_num;
    	req.u.dpcd_write.dpcd_address = offset;
    	req.u.dpcd_write.num_bytes = num_bytes;
    	req.u.dpcd_write.bytes = bytes;
    	drm_dp_encode_sideband_req(&req, msg);
    
    	return 0;
    }
    
    static int build_link_address(struct drm_dp_sideband_msg_tx *msg)
    {
    	struct drm_dp_sideband_msg_req_body req;
    
    	req.req_type = DP_LINK_ADDRESS;
    	drm_dp_encode_sideband_req(&req, msg);
    	return 0;
    }
    
    static int build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg, int port_num)
    {
    	struct drm_dp_sideband_msg_req_body req;
    
    	req.req_type = DP_ENUM_PATH_RESOURCES;
    	req.u.port_num.port_number = port_num;
    	drm_dp_encode_sideband_req(&req, msg);
    	msg->path_msg = true;
    	return 0;
    }
    
    static int build_allocate_payload(struct drm_dp_sideband_msg_tx *msg, int port_num,
    				  u8 vcpi, uint16_t pbn,
    				  u8 number_sdp_streams,
    				  u8 *sdp_stream_sink)
    {
    	struct drm_dp_sideband_msg_req_body req;
    	memset(&req, 0, sizeof(req));
    	req.req_type = DP_ALLOCATE_PAYLOAD;
    	req.u.allocate_payload.port_number = port_num;
    	req.u.allocate_payload.vcpi = vcpi;
    	req.u.allocate_payload.pbn = pbn;
    	req.u.allocate_payload.number_sdp_streams = number_sdp_streams;
    	memcpy(req.u.allocate_payload.sdp_stream_sink, sdp_stream_sink,
    		   number_sdp_streams);
    	drm_dp_encode_sideband_req(&req, msg);
    	msg->path_msg = true;
    	return 0;
    }
    
    static int drm_dp_mst_assign_payload_id(struct drm_dp_mst_topology_mgr *mgr,
    					struct drm_dp_vcpi *vcpi)
    {
    	int ret, vcpi_ret;
    
    	mutex_lock(&mgr->payload_lock);
    	ret = find_first_zero_bit(&mgr->payload_mask, mgr->max_payloads + 1);
    	if (ret > mgr->max_payloads) {
    		ret = -EINVAL;
    		DRM_DEBUG_KMS("out of payload ids %d\n", ret);
    		goto out_unlock;
    	}
    
    	vcpi_ret = find_first_zero_bit(&mgr->vcpi_mask, mgr->max_payloads + 1);
    	if (vcpi_ret > mgr->max_payloads) {
    		ret = -EINVAL;
    		DRM_DEBUG_KMS("out of vcpi ids %d\n", ret);
    		goto out_unlock;
    	}
    
    	set_bit(ret, &mgr->payload_mask);
    	set_bit(vcpi_ret, &mgr->vcpi_mask);
    	vcpi->vcpi = vcpi_ret + 1;
    	mgr->proposed_vcpis[ret - 1] = vcpi;
    out_unlock:
    	mutex_unlock(&mgr->payload_lock);
    	return ret;
    }
    
    static void drm_dp_mst_put_payload_id(struct drm_dp_mst_topology_mgr *mgr,
    				      int vcpi)
    {
    	int i;
    	if (vcpi == 0)
    		return;
    
    	mutex_lock(&mgr->payload_lock);
    	DRM_DEBUG_KMS("putting payload %d\n", vcpi);
    	clear_bit(vcpi - 1, &mgr->vcpi_mask);
    
    	for (i = 0; i < mgr->max_payloads; i++) {
    		if (mgr->proposed_vcpis[i])
    			if (mgr->proposed_vcpis[i]->vcpi == vcpi) {
    				mgr->proposed_vcpis[i] = NULL;
    				clear_bit(i + 1, &mgr->payload_mask);
    			}
    	}
    	mutex_unlock(&mgr->payload_lock);
    }
    
    static bool check_txmsg_state(struct drm_dp_mst_topology_mgr *mgr,
    			      struct drm_dp_sideband_msg_tx *txmsg)
    {
    	bool ret;
    
    	/*
    	 * All updates to txmsg->state are protected by mgr->qlock, and the two
    	 * cases we check here are terminal states. For those the barriers
    	 * provided by the wake_up/wait_event pair are enough.
    	 */
    	ret = (txmsg->state == DRM_DP_SIDEBAND_TX_RX ||
    	       txmsg->state == DRM_DP_SIDEBAND_TX_TIMEOUT);
    	return ret;
    }
    
    static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb,
    				    struct drm_dp_sideband_msg_tx *txmsg)
    {
    	struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;
    	int ret;
    
    	ret = wait_event_timeout(mgr->tx_waitq,
    				 check_txmsg_state(mgr, txmsg),
    				 (4 * HZ));
    	mutex_lock(&mstb->mgr->qlock);
    	if (ret > 0) {
    		if (txmsg->state == DRM_DP_SIDEBAND_TX_TIMEOUT) {
    			ret = -EIO;
    			goto out;
    		}
    	} else {
    		DRM_DEBUG_KMS("timedout msg send %p %d %d\n", txmsg, txmsg->state, txmsg->seqno);
    
    		/* dump some state */
    		ret = -EIO;
    
    		/* remove from q */
    		if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED ||
    		    txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) {
    			list_del(&txmsg->next);
    		}
    
    		if (txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND ||
    		    txmsg->state == DRM_DP_SIDEBAND_TX_SENT) {
    			mstb->tx_slots[txmsg->seqno] = NULL;
    		}
    	}
    out:
    	mutex_unlock(&mgr->qlock);
    
    	return ret;
    }
    
    static struct drm_dp_mst_branch *drm_dp_add_mst_branch_device(u8 lct, u8 *rad)
    {
    	struct drm_dp_mst_branch *mstb;
    
    	mstb = kzalloc(sizeof(*mstb), GFP_KERNEL);
    	if (!mstb)
    		return NULL;
    
    	mstb->lct = lct;
    	if (lct > 1)
    		memcpy(mstb->rad, rad, lct / 2);
    	INIT_LIST_HEAD(&mstb->ports);
    	kref_init(&mstb->kref);
    	return mstb;
    }
    
    static void drm_dp_destroy_mst_branch_device(struct kref *kref)
    {
    	struct drm_dp_mst_branch *mstb = container_of(kref, struct drm_dp_mst_branch, kref);
    	struct drm_dp_mst_port *port, *tmp;
    	bool wake_tx = false;
    
    	/*
    	 * destroy all ports - don't need lock
    	 * as there are no more references to the mst branch
    	 * device at this point.
    	 */
    	list_for_each_entry_safe(port, tmp, &mstb->ports, next) {
    		list_del(&port->next);
    		drm_dp_put_port(port);
    	}
    
    	/* drop any tx slots msg */
    	mutex_lock(&mstb->mgr->qlock);
    	if (mstb->tx_slots[0]) {
    		mstb->tx_slots[0]->state = DRM_DP_SIDEBAND_TX_TIMEOUT;
    		mstb->tx_slots[0] = NULL;
    		wake_tx = true;
    	}
    	if (mstb->tx_slots[1]) {
    		mstb->tx_slots[1]->state = DRM_DP_SIDEBAND_TX_TIMEOUT;
    		mstb->tx_slots[1] = NULL;
    		wake_tx = true;
    	}
    	mutex_unlock(&mstb->mgr->qlock);
    
    	if (wake_tx)
    		wake_up(&mstb->mgr->tx_waitq);
    	kfree(mstb);
    }
    
    static void drm_dp_put_mst_branch_device(struct drm_dp_mst_branch *mstb)
    {
    	kref_put(&mstb->kref, drm_dp_destroy_mst_branch_device);
    }
    
    
    static void drm_dp_port_teardown_pdt(struct drm_dp_mst_port *port, int old_pdt)
    {
    	struct drm_dp_mst_branch *mstb;
    
    	switch (old_pdt) {
    	case DP_PEER_DEVICE_DP_LEGACY_CONV:
    	case DP_PEER_DEVICE_SST_SINK:
    		/* remove i2c over sideband */
    		drm_dp_mst_unregister_i2c_bus(&port->aux);
    		break;
    	case DP_PEER_DEVICE_MST_BRANCHING:
    		mstb = port->mstb;
    		port->mstb = NULL;
    		drm_dp_put_mst_branch_device(mstb);
    		break;
    	}
    }
    
    static void drm_dp_destroy_port(struct kref *kref)
    {
    	struct drm_dp_mst_port *port = container_of(kref, struct drm_dp_mst_port, kref);
    	struct drm_dp_mst_topology_mgr *mgr = port->mgr;
    
    	if (!port->input) {
    		port->vcpi.num_slots = 0;
    
    		kfree(port->cached_edid);
    
    		/*
    		 * The only time we don't have a connector
    		 * on an output port is if the connector init
    		 * fails.
    		 */
    		if (port->connector) {
    			/* we can't destroy the connector here, as
    			 * we might be holding the mode_config.mutex
    			 * from an EDID retrieval */
    
    			mutex_lock(&mgr->destroy_connector_lock);
    			list_add(&port->next, &mgr->destroy_connector_list);
    			mutex_unlock(&mgr->destroy_connector_lock);
    			schedule_work(&mgr->destroy_connector_work);
    			return;
    		}
    		/* no need to clean up vcpi
    		 * as if we have no connector we never setup a vcpi */
    		drm_dp_port_teardown_pdt(port, port->pdt);
    	}
    	kfree(port);
    }
    
    static void drm_dp_put_port(struct drm_dp_mst_port *port)
    {
    	kref_put(&port->kref, drm_dp_destroy_port);
    }
    
    static struct drm_dp_mst_branch *drm_dp_mst_get_validated_mstb_ref_locked(struct drm_dp_mst_branch *mstb, struct drm_dp_mst_branch *to_find)
    {
    	struct drm_dp_mst_port *port;
    	struct drm_dp_mst_branch *rmstb;
    	if (to_find == mstb) {
    		kref_get(&mstb->kref);
    		return mstb;
    	}
    	list_for_each_entry(port, &mstb->ports, next) {
    		if (port->mstb) {
    			rmstb = drm_dp_mst_get_validated_mstb_ref_locked(port->mstb, to_find);
    			if (rmstb)
    				return rmstb;
    		}
    	}
    	return NULL;
    }
    
    static struct drm_dp_mst_branch *drm_dp_get_validated_mstb_ref(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_branch *mstb)
    {
    	struct drm_dp_mst_branch *rmstb = NULL;
    	mutex_lock(&mgr->lock);
    	if (mgr->mst_primary)
    		rmstb = drm_dp_mst_get_validated_mstb_ref_locked(mgr->mst_primary, mstb);
    	mutex_unlock(&mgr->lock);
    	return rmstb;
    }
    
    static struct drm_dp_mst_port *drm_dp_mst_get_port_ref_locked(struct drm_dp_mst_branch *mstb, struct drm_dp_mst_port *to_find)
    {
    	struct drm_dp_mst_port *port, *mport;
    
    	list_for_each_entry(port, &mstb->ports, next) {
    		if (port == to_find) {
    			kref_get(&port->kref);
    			return port;
    		}
    		if (port->mstb) {
    			mport = drm_dp_mst_get_port_ref_locked(port->mstb, to_find);
    			if (mport)
    				return mport;
    		}
    	}
    	return NULL;
    }
    
    static struct drm_dp_mst_port *drm_dp_get_validated_port_ref(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
    {
    	struct drm_dp_mst_port *rport = NULL;
    	mutex_lock(&mgr->lock);
    	if (mgr->mst_primary)
    		rport = drm_dp_mst_get_port_ref_locked(mgr->mst_primary, port);
    	mutex_unlock(&mgr->lock);
    	return rport;
    }
    
    static struct drm_dp_mst_port *drm_dp_get_port(struct drm_dp_mst_branch *mstb, u8 port_num)
    {
    	struct drm_dp_mst_port *port;
    
    	list_for_each_entry(port, &mstb->ports, next) {
    		if (port->port_num == port_num) {
    			kref_get(&port->kref);
    			return port;
    		}
    	}
    
    	return NULL;
    }
    
    /*
     * calculate a new RAD for this MST branch device
     * if parent has an LCT of 2 then it has 1 nibble of RAD,
     * if parent has an LCT of 3 then it has 2 nibbles of RAD,
     */
    static u8 drm_dp_calculate_rad(struct drm_dp_mst_port *port,
    				 u8 *rad)
    {
    	int parent_lct = port->parent->lct;
    	int shift = 4;
    	int idx = (parent_lct - 1) / 2;
    	if (parent_lct > 1) {
    		memcpy(rad, port->parent->rad, idx + 1);
    		shift = (parent_lct % 2) ? 4 : 0;
    	} else
    		rad[0] = 0;
    
    	rad[idx] |= port->port_num << shift;
    	return parent_lct + 1;
    }
    
    /*
     * return sends link address for new mstb
     */
    static bool drm_dp_port_setup_pdt(struct drm_dp_mst_port *port)
    {
    	int ret;
    	u8 rad[6], lct;
    	bool send_link = false;
    	switch (port->pdt) {
    	case DP_PEER_DEVICE_DP_LEGACY_CONV:
    	case DP_PEER_DEVICE_SST_SINK:
    		/* add i2c over sideband */
    		ret = drm_dp_mst_register_i2c_bus(&port->aux);
    		break;
    	case DP_PEER_DEVICE_MST_BRANCHING:
    		lct = drm_dp_calculate_rad(port, rad);
    
    		port->mstb = drm_dp_add_mst_branch_device(lct, rad);
    		port->mstb->mgr = port->mgr;
    		port->mstb->port_parent = port;
    
    		send_link = true;
    		break;
    	}
    	return send_link;
    }
    
    static void drm_dp_check_port_guid(struct drm_dp_mst_branch *mstb,
    				   struct drm_dp_mst_port *port)
    {
    	int ret;
    	if (port->dpcd_rev >= 0x12) {
    		port->guid_valid = drm_dp_validate_guid(mstb->mgr, port->guid);
    		if (!port->guid_valid) {
    			ret = drm_dp_send_dpcd_write(mstb->mgr,
    						     port,
    						     DP_GUID,
    						     16, port->guid);
    			port->guid_valid = true;
    		}
    	}
    }
    
    static void build_mst_prop_path(const struct drm_dp_mst_branch *mstb,
    				int pnum,
    				char *proppath,
    				size_t proppath_size)
    {
    	int i;
    	char temp[8];
    	snprintf(proppath, proppath_size, "mst:%d", mstb->mgr->conn_base_id);
    	for (i = 0; i < (mstb->lct - 1); i++) {
    		int shift = (i % 2) ? 0 : 4;
    		int port_num = (mstb->rad[i / 2] >> shift) & 0xf;
    		snprintf(temp, sizeof(temp), "-%d", port_num);
    		strlcat(proppath, temp, proppath_size);
    	}
    	snprintf(temp, sizeof(temp), "-%d", pnum);
    	strlcat(proppath, temp, proppath_size);
    }
    
    static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
    			    struct device *dev,
    			    struct drm_dp_link_addr_reply_port *port_msg)
    {
    	struct drm_dp_mst_port *port;
    	bool ret;
    	bool created = false;
    	int old_pdt = 0;
    	int old_ddps = 0;
    	port = drm_dp_get_port(mstb, port_msg->port_number);
    	if (!port) {
    		port = kzalloc(sizeof(*port), GFP_KERNEL);
    		if (!port)
    			return;
    		kref_init(&port->kref);
    		port->parent = mstb;
    		port->port_num = port_msg->port_number;
    		port->mgr = mstb->mgr;
    		port->aux.name = "DPMST";
    		port->aux.dev = dev;
    		created = true;
    	} else {
    		old_pdt = port->pdt;
    		old_ddps = port->ddps;
    	}
    
    	port->pdt = port_msg->peer_device_type;
    	port->input = port_msg->input_port;
    	port->mcs = port_msg->mcs;
    	port->ddps = port_msg->ddps;
    	port->ldps = port_msg->legacy_device_plug_status;
    	port->dpcd_rev = port_msg->dpcd_revision;
    	port->num_sdp_streams = port_msg->num_sdp_streams;
    	port->num_sdp_stream_sinks = port_msg->num_sdp_stream_sinks;
    	memcpy(port->guid, port_msg->peer_guid, 16);
    
    	/* manage mstb port lists with mgr lock - take a reference
    	   for this list */
    	if (created) {
    		mutex_lock(&mstb->mgr->lock);
    		kref_get(&port->kref);
    		list_add(&port->next, &mstb->ports);
    		mutex_unlock(&mstb->mgr->lock);
    	}
    
    	if (old_ddps != port->ddps) {
    		if (port->ddps) {
    			drm_dp_check_port_guid(mstb, port);
    			if (!port->input)
    				drm_dp_send_enum_path_resources(mstb->mgr, mstb, port);
    		} else {
    			port->guid_valid = false;
    			port->available_pbn = 0;
    			}
    	}
    
    	if (old_pdt != port->pdt && !port->input) {
    		drm_dp_port_teardown_pdt(port, old_pdt);
    
    		ret = drm_dp_port_setup_pdt(port);
    		if (ret == true)
    			drm_dp_send_link_address(mstb->mgr, port->mstb);
    	}
    
    	if (created && !port->input) {
    		char proppath[255];
    
    		build_mst_prop_path(mstb, port->port_num, proppath, sizeof(proppath));
    		port->connector = (*mstb->mgr->cbs->add_connector)(mstb->mgr, port, proppath);
    		if (!port->connector) {
    			/* remove it from the port list */
    			mutex_lock(&mstb->mgr->lock);
    			list_del(&port->next);
    			mutex_unlock(&mstb->mgr->lock);
    			/* drop port list reference */
    			drm_dp_put_port(port);
    			goto out;
    		}
    		if (port->port_num >= DP_MST_LOGICAL_PORT_0) {
    			port->cached_edid = drm_get_edid(port->connector, &port->aux.ddc);
    			drm_mode_connector_set_tile_property(port->connector);
    		}
    		(*mstb->mgr->cbs->register_connector)(port->connector);
    	}
    
    out:
    	/* put reference to this port */
    	drm_dp_put_port(port);
    }
    
    static void drm_dp_update_port(struct drm_dp_mst_branch *mstb,
    			       struct drm_dp_connection_status_notify *conn_stat)
    {
    	struct drm_dp_mst_port *port;
    	int old_pdt;
    	int old_ddps;
    	bool dowork = false;
    	port = drm_dp_get_port(mstb, conn_stat->port_number);
    	if (!port)
    		return;
    
    	old_ddps = port->ddps;
    	old_pdt = port->pdt;
    	port->pdt = conn_stat->peer_device_type;
    	port->mcs = conn_stat->message_capability_status;
    	port->ldps = conn_stat->legacy_device_plug_status;
    	port->ddps = conn_stat->displayport_device_plug_status;
    
    	if (old_ddps != port->ddps) {
    		if (port->ddps) {
    			drm_dp_check_port_guid(mstb, port);
    			dowork = true;
    		} else {
    			port->guid_valid = false;
    			port->available_pbn = 0;
    		}
    	}
    	if (old_pdt != port->pdt && !port->input) {
    		drm_dp_port_teardown_pdt(port, old_pdt);
    
    		if (drm_dp_port_setup_pdt(port))
    			dowork = true;
    	}
    
    	drm_dp_put_port(port);
    	if (dowork)
    		queue_work(system_long_wq, &mstb->mgr->work);
    
    }
    
    static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_topology_mgr *mgr,
    							       u8 lct, u8 *rad)
    {
    	struct drm_dp_mst_branch *mstb;
    	struct drm_dp_mst_port *port;
    	int i;
    	/* find the port by iterating down */
    
    	mutex_lock(&mgr->lock);
    	mstb = mgr->mst_primary;
    
    	for (i = 0; i < lct - 1; i++) {
    		int shift = (i % 2) ? 0 : 4;
    		int port_num = (rad[i / 2] >> shift) & 0xf;
    
    		list_for_each_entry(port, &mstb->ports, next) {
    			if (port->port_num == port_num) {
    				mstb = port->mstb;
    				if (!mstb) {
    					DRM_ERROR("failed to lookup MSTB with lct %d, rad %02x\n", lct, rad[0]);
    					goto out;
    				}
    
    				break;
    			}
    		}
    	}
    	kref_get(&mstb->kref);
    out:
    	mutex_unlock(&mgr->lock);
    	return mstb;
    }
    
    static struct drm_dp_mst_branch *get_mst_branch_device_by_guid_helper(
    	struct drm_dp_mst_branch *mstb,
    	uint8_t *guid)
    {
    	struct drm_dp_mst_branch *found_mstb;
    	struct drm_dp_mst_port *port;
    
    	list_for_each_entry(port, &mstb->ports, next) {
    		if (!port->mstb)
    			continue;
    
    		if (port->guid_valid && memcmp(port->guid, guid, 16) == 0)
    			return port->mstb;
    
    		found_mstb = get_mst_branch_device_by_guid_helper(port->mstb, guid);
    
    		if (found_mstb)
    			return found_mstb;
    	}
    
    	return NULL;
    }
    
    static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device_by_guid(
    	struct drm_dp_mst_topology_mgr *mgr,
    	uint8_t *guid)
    {
    	struct drm_dp_mst_branch *mstb;
    
    	/* find the port by iterating down */
    	mutex_lock(&mgr->lock);
    
    	if (mgr->guid_valid && memcmp(mgr->guid, guid, 16) == 0)
    		mstb = mgr->mst_primary;
    	else
    		mstb = get_mst_branch_device_by_guid_helper(mgr->mst_primary, guid);
    
    	if (mstb)
    		kref_get(&mstb->kref);
    
    	mutex_unlock(&mgr->lock);
    	return mstb;
    }
    
    static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
    					       struct drm_dp_mst_branch *mstb)
    {
    	struct drm_dp_mst_port *port;
    	struct drm_dp_mst_branch *mstb_child;
    	if (!mstb->link_address_sent)
    		drm_dp_send_link_address(mgr, mstb);
    
    	list_for_each_entry(port, &mstb->ports, next) {
    		if (port->input)
    			continue;
    
    		if (!port->ddps)
    			continue;
    
    		if (!port->available_pbn)
    			drm_dp_send_enum_path_resources(mgr, mstb, port);
    
    		if (port->mstb) {
    			mstb_child = drm_dp_get_validated_mstb_ref(mgr, port->mstb);
    			if (mstb_child) {
    				drm_dp_check_and_send_link_address(mgr, mstb_child);
    				drm_dp_put_mst_branch_device(mstb_child);
    			}
    		}
    	}
    }
    
    static void drm_dp_mst_link_probe_work(struct work_struct *work)
    {
    	struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, work);
    	struct drm_dp_mst_branch *mstb;
    
    	mutex_lock(&mgr->lock);
    	mstb = mgr->mst_primary;
    	if (mstb) {
    		kref_get(&mstb->kref);
    	}
    	mutex_unlock(&mgr->lock);
    	if (mstb) {
    		drm_dp_check_and_send_link_address(mgr, mstb);
    		drm_dp_put_mst_branch_device(mstb);
    	}
    }
    
    static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
    				 u8 *guid)
    {
    	static u8 zero_guid[16];
    
    	if (!memcmp(guid, zero_guid, 16)) {
    		u64 salt = get_jiffies_64();
    		memcpy(&guid[0], &salt, sizeof(u64));
    		memcpy(&guid[8], &salt, sizeof(u64));
    		return false;
    	}
    	return true;
    }
    
    #if 0
    static int build_dpcd_read(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32 offset, u8 num_bytes)
    {
    	struct drm_dp_sideband_msg_req_body req;
    
    	req.req_type = DP_REMOTE_DPCD_READ;
    	req.u.dpcd_read.port_number = port_num;
    	req.u.dpcd_read.dpcd_address = offset;
    	req.u.dpcd_read.num_bytes = num_bytes;
    	drm_dp_encode_sideband_req(&req, msg);
    
    	return 0;
    }
    #endif
    
    static int drm_dp_send_sideband_msg(struct drm_dp_mst_topology_mgr *mgr,
    				    bool up, u8 *msg, int len)
    {
    	int ret;
    	int regbase = up ? DP_SIDEBAND_MSG_UP_REP_BASE : DP_SIDEBAND_MSG_DOWN_REQ_BASE;
    	int tosend, total, offset;
    	int retries = 0;
    
    retry:
    	total = len;
    	offset = 0;
    	do {
    		tosend = min3(mgr->max_dpcd_transaction_bytes, 16, total);
    
    		ret = drm_dp_dpcd_write(mgr->aux, regbase + offset,
    					&msg[offset],
    					tosend);
    		if (ret != tosend) {
    			if (ret == -EIO && retries < 5) {
    				retries++;
    				goto retry;
    			}
    			DRM_DEBUG_KMS("failed to dpcd write %d %d\n", tosend, ret);
    
    			return -EIO;
    		}
    		offset += tosend;
    		total -= tosend;
    	} while (total > 0);
    	return 0;
    }
    
    static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr,
    				  struct drm_dp_sideband_msg_tx *txmsg)
    {
    	struct drm_dp_mst_branch *mstb = txmsg->dst;
    	u8 req_type;
    
    	/* both msg slots are full */
    	if (txmsg->seqno == -1) {
    		if (mstb->tx_slots[0] && mstb->tx_slots[1]) {
    			DRM_DEBUG_KMS("%s: failed to find slot\n", __func__);
    			return -EAGAIN;
    		}
    		if (mstb->tx_slots[0] == NULL && mstb->tx_slots[1] == NULL) {
    			txmsg->seqno = mstb->last_seqno;
    			mstb->last_seqno ^= 1;
    		} else if (mstb->tx_slots[0] == NULL)
    			txmsg->seqno = 0;
    		else
    			txmsg->seqno = 1;
    		mstb->tx_slots[txmsg->seqno] = txmsg;
    	}
    
    	req_type = txmsg->msg[0] & 0x7f;
    	if (req_type == DP_CONNECTION_STATUS_NOTIFY ||
    		req_type == DP_RESOURCE_STATUS_NOTIFY)
    		hdr->broadcast = 1;
    	else
    		hdr->broadcast = 0;
    	hdr->path_msg = txmsg->path_msg;
    	hdr->lct = mstb->lct;
    	hdr->lcr = mstb->lct - 1;
    	if (mstb->lct > 1)
    		memcpy(hdr->rad, mstb->rad, mstb->lct / 2);
    	hdr->seqno = txmsg->seqno;
    	return 0;
    }
    /*
     * process a single block of the next message in the sideband queue
     */
    static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr,
    				   struct drm_dp_sideband_msg_tx *txmsg,
    				   bool up)
    {
    	u8 chunk[48];
    	struct drm_dp_sideband_msg_hdr hdr;
    	int len, space, idx, tosend;
    	int ret;
    
    	memset(&hdr, 0, sizeof(struct drm_dp_sideband_msg_hdr));
    
    	if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) {
    		txmsg->seqno = -1;
    		txmsg->state = DRM_DP_SIDEBAND_TX_START_SEND;
    	}
    
    	/* make hdr from dst mst - for replies use seqno
    	   otherwise assign one */
    	ret = set_hdr_from_dst_qlock(&hdr, txmsg);
    	if (ret < 0)
    		return ret;
    
    	/* amount left to send in this message */
    	len = txmsg->cur_len - txmsg->cur_offset;
    
    	/* 48 - sideband msg size - 1 byte for data CRC, x header bytes */
    	space = 48 - 1 - drm_dp_calc_sb_hdr_size(&hdr);
    
    	tosend = min(len, space);
    	if (len == txmsg->cur_len)
    		hdr.somt = 1;
    	if (space >= len)
    		hdr.eomt = 1;
    
    
    	hdr.msg_len = tosend + 1;
    	drm_dp_encode_sideband_msg_hdr(&hdr, chunk, &idx);
    	memcpy(&chunk[idx], &txmsg->msg[txmsg->cur_offset], tosend);
    	/* add crc at end */
    	drm_dp_crc_sideband_chunk_req(&chunk[idx], tosend);
    	idx += tosend + 1;
    
    	ret = drm_dp_send_sideband_msg(mgr, up, chunk, idx);
    	if (ret) {
    		DRM_DEBUG_KMS("sideband msg failed to send\n");
    		return ret;
    	}
    
    	txmsg->cur_offset += tosend;
    	if (txmsg->cur_offset == txmsg->cur_len) {
    		txmsg->state = DRM_DP_SIDEBAND_TX_SENT;
    		return 1;
    	}
    	return 0;
    }
    
    static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr)
    {
    	struct drm_dp_sideband_msg_tx *txmsg;
    	int ret;
    
    	WARN_ON(!mutex_is_locked(&mgr->qlock));
    
    	/* construct a chunk from the first msg in the tx_msg queue */
    	if (list_empty(&mgr->tx_msg_downq)) {
    		mgr->tx_down_in_progress = false;
    		return;
    	}
    	mgr->tx_down_in_progress = true;
    
    	txmsg = list_first_entry(&mgr->tx_msg_downq, struct drm_dp_sideband_msg_tx, next);
    	ret = process_single_tx_qlock(mgr, txmsg, false);
    	if (ret == 1) {
    		/* txmsg is sent it should be in the slots now */
    		list_del(&txmsg->next);
    	} else if (ret) {
    		DRM_DEBUG_KMS("failed to send msg in q %d\n", ret);
    		list_del(&txmsg->next);
    		if (txmsg->seqno != -1)
    			txmsg->dst->tx_slots[txmsg->seqno] = NULL;
    		txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT;
    		wake_up(&mgr->tx_waitq);
    	}
    	if (list_empty(&mgr->tx_msg_downq)) {
    		mgr->tx_down_in_progress = false;
    		return;
    	}
    }
    
    /* called holding qlock */
    static void process_single_up_tx_qlock(struct drm_dp_mst_topology_mgr *mgr,
    				       struct drm_dp_sideband_msg_tx *txmsg)
    {
    	int ret;
    
    	/* construct a chunk from the first msg in the tx_msg queue */
    	ret = process_single_tx_qlock(mgr, txmsg, true);
    
    	if (ret != 1)
    		DRM_DEBUG_KMS("failed to send msg in q %d\n", ret);
    
    	txmsg->dst->tx_slots[txmsg->seqno] = NULL;
    }
    
    static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr,
    				 struct drm_dp_sideband_msg_tx *txmsg)
    {
    	mutex_lock(&mgr->qlock);
    	list_add_tail(&txmsg->next, &mgr->tx_msg_downq);
    	if (!mgr->tx_down_in_progress)
    		process_single_down_tx_qlock(mgr);
    	mutex_unlock(&mgr->qlock);
    }
    
    static void drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
    				     struct drm_dp_mst_branch *mstb)
    {
    	int len;
    	struct drm_dp_sideband_msg_tx *txmsg;
    	int ret;
    
    	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
    	if (!txmsg)
    		return;
    
    	txmsg->dst = mstb;
    	len = build_link_address(txmsg);
    
    	mstb->link_address_sent = true;
    	drm_dp_queue_down_tx(mgr, txmsg);
    
    	ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
    	if (ret > 0) {
    		int i;
    
    		if (txmsg->reply.reply_type == 1)
    			DRM_DEBUG_KMS("link address nak received\n");
    		else {
    			DRM_DEBUG_KMS("link address reply: %d\n", txmsg->reply.u.link_addr.nports);
    			for (i = 0; i < txmsg->reply.u.link_addr.nports; i++) {
    				DRM_DEBUG_KMS("port %d: input %d, pdt: %d, pn: %d, dpcd_rev: %02x, mcs: %d, ddps: %d, ldps %d, sdp %d/%d\n", i,
    				       txmsg->reply.u.link_addr.ports[i].input_port,
    				       txmsg->reply.u.link_addr.ports[i].peer_device_type,
    				       txmsg->reply.u.link_addr.ports[i].port_number,
    				       txmsg->reply.u.link_addr.ports[i].dpcd_revision,
    				       txmsg->reply.u.link_addr.ports[i].mcs,
    				       txmsg->reply.u.link_addr.ports[i].ddps,
    				       txmsg->reply.u.link_addr.ports[i].legacy_device_plug_status,
    				       txmsg->reply.u.link_addr.ports[i].num_sdp_streams,
    				       txmsg->reply.u.link_addr.ports[i].num_sdp_stream_sinks);
    			}
    			for (i = 0; i < txmsg->reply.u.link_addr.nports; i++) {
    				drm_dp_add_port(mstb, mgr->dev, &txmsg->reply.u.link_addr.ports[i]);
    			}
    			(*mgr->cbs->hotplug)(mgr);
    		}
    	} else {
    		mstb->link_address_sent = false;
    		DRM_DEBUG_KMS("link address failed %d\n", ret);
    	}
    
    	kfree(txmsg);
    }
    
    static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
    					   struct drm_dp_mst_branch *mstb,
    					   struct drm_dp_mst_port *port)
    {
    	int len;
    	struct drm_dp_sideband_msg_tx *txmsg;
    	int ret;
    
    	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
    	if (!txmsg)
    		return -ENOMEM;
    
    	txmsg->dst = mstb;
    	len = build_enum_path_resources(txmsg, port->port_num);
    
    	drm_dp_queue_down_tx(mgr, txmsg);
    
    	ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
    	if (ret > 0) {
    		if (txmsg->reply.reply_type == 1)
    			DRM_DEBUG_KMS("enum path resources nak received\n");
    		else {
    			if (port->port_num != txmsg->reply.u.path_resources.port_number)
    				DRM_ERROR("got incorrect port in response\n");
    			DRM_DEBUG_KMS("enum path resources %d: %d %d\n", txmsg->reply.u.path_resources.port_number, txmsg->reply.u.path_resources.full_payload_bw_number,
    			       txmsg->reply.u.path_resources.avail_payload_bw_number);
    			port->available_pbn = txmsg->reply.u.path_resources.avail_payload_bw_number;
    		}
    	}
    
    	kfree(txmsg);
    	return 0;
    }
    
    static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr,
    				   struct drm_dp_mst_port *port,
    				   int id,
    				   int pbn)
    {
    	struct drm_dp_sideband_msg_tx *txmsg;
    	struct drm_dp_mst_branch *mstb;
    	int len, ret;
    	u8 sinks[DRM_DP_MAX_SDP_STREAMS];
    	int i;
    
    	mstb = drm_dp_get_validated_mstb_ref(mgr, port->parent);
    	if (!mstb)
    		return -EINVAL;
    
    	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
    	if (!txmsg) {
    		ret = -ENOMEM;
    		goto fail_put;
    	}
    
    	for (i = 0; i < port->num_sdp_streams; i++)
    		sinks[i] = i;
    
    	txmsg->dst = mstb;
    	len = build_allocate_payload(txmsg, port->port_num,
    				     id,
    				     pbn, port->num_sdp_streams, sinks);
    
    	drm_dp_queue_down_tx(mgr, txmsg);
    
    	ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
    	if (ret > 0) {
    		if (txmsg->reply.reply_type == 1) {
    			ret = -EINVAL;
    		} else
    			ret = 0;
    	}
    	kfree(txmsg);
    fail_put:
    	drm_dp_put_mst_branch_device(mstb);
    	return ret;
    }
    
    static int drm_dp_create_payload_step1(struct drm_dp_mst_topology_mgr *mgr,
    				       int id,
    				       struct drm_dp_payload *payload)
    {
    	int ret;
    
    	ret = drm_dp_dpcd_write_payload(mgr, id, payload);
    	if (ret < 0) {
    		payload->payload_state = 0;
    		return ret;
    	}
    	payload->payload_state = DP_PAYLOAD_LOCAL;
    	return 0;
    }
    
    static int drm_dp_create_payload_step2(struct drm_dp_mst_topology_mgr *mgr,
    				       struct drm_dp_mst_port *port,
    				       int id,
    				       struct drm_dp_payload *payload)
    {
    	int ret;
    	ret = drm_dp_payload_send_msg(mgr, port, id, port->vcpi.pbn);
    	if (ret < 0)
    		return ret;
    	payload->payload_state = DP_PAYLOAD_REMOTE;
    	return ret;
    }
    
    static int drm_dp_destroy_payload_step1(struct drm_dp_mst_topology_mgr *mgr,
    					struct drm_dp_mst_port *port,
    					int id,
    					struct drm_dp_payload *payload)
    {
    	DRM_DEBUG_KMS("\n");
    	/* its okay for these to fail */
    	if (port) {
    		drm_dp_payload_send_msg(mgr, port, id, 0);
    	}
    
    	drm_dp_dpcd_write_payload(mgr, id, payload);
    	payload->payload_state = DP_PAYLOAD_DELETE_LOCAL;
    	return 0;
    }
    
    static int drm_dp_destroy_payload_step2(struct drm_dp_mst_topology_mgr *mgr,
    					int id,
    					struct drm_dp_payload *payload)
    {
    	payload->payload_state = 0;
    	return 0;
    }
    
    /**
     * drm_dp_update_payload_part1() - Execute payload update part 1
     * @mgr: manager to use.
     *
     * This iterates over all proposed virtual channels, and tries to
     * allocate space in the link for them. For 0->slots transitions,
     * this step just writes the VCPI to the MST device. For slots->0
     * transitions, this writes the updated VCPIs and removes the
     * remote VC payloads.
     *
     * after calling this the driver should generate ACT and payload
     * packets.
     */
    int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
    {
    	int i, j;
    	int cur_slots = 1;
    	struct drm_dp_payload req_payload;
    	struct drm_dp_mst_port *port;
    
    	mutex_lock(&mgr->payload_lock);
    	for (i = 0; i < mgr->max_payloads; i++) {
    		/* solve the current payloads - compare to the hw ones
    		   - update the hw view */
    		req_payload.start_slot = cur_slots;
    		if (mgr->proposed_vcpis[i]) {
    			port = container_of(mgr->proposed_vcpis[i], struct drm_dp_mst_port, vcpi);
    			req_payload.num_slots = mgr->proposed_vcpis[i]->num_slots;
    			req_payload.vcpi = mgr->proposed_vcpis[i]->vcpi;
    		} else {
    			port = NULL;
    			req_payload.num_slots = 0;
    		}
    
    		if (mgr->payloads[i].start_slot != req_payload.start_slot) {
    			mgr->payloads[i].start_slot = req_payload.start_slot;
    		}
    		/* work out what is required to happen with this payload */
    		if (mgr->payloads[i].num_slots != req_payload.num_slots) {
    
    			/* need to push an update for this payload */
    			if (req_payload.num_slots) {
    				drm_dp_create_payload_step1(mgr, mgr->proposed_vcpis[i]->vcpi, &req_payload);
    				mgr->payloads[i].num_slots = req_payload.num_slots;
    				mgr->payloads[i].vcpi = req_payload.vcpi;
    			} else if (mgr->payloads[i].num_slots) {
    				mgr->payloads[i].num_slots = 0;
    				drm_dp_destroy_payload_step1(mgr, port, port->vcpi.vcpi, &mgr->payloads[i]);
    				req_payload.payload_state = mgr->payloads[i].payload_state;
    				mgr->payloads[i].start_slot = 0;
    			}
    			mgr->payloads[i].payload_state = req_payload.payload_state;
    		}
    		cur_slots += req_payload.num_slots;
    	}
    
    	for (i = 0; i < mgr->max_payloads; i++) {
    		if (mgr->payloads[i].payload_state == DP_PAYLOAD_DELETE_LOCAL) {
    			DRM_DEBUG_KMS("removing payload %d\n", i);
    			for (j = i; j < mgr->max_payloads - 1; j++) {
    				memcpy(&mgr->payloads[j], &mgr->payloads[j + 1], sizeof(struct drm_dp_payload));
    				mgr->proposed_vcpis[j] = mgr->proposed_vcpis[j + 1];
    				if (mgr->proposed_vcpis[j] && mgr->proposed_vcpis[j]->num_slots) {
    					set_bit(j + 1, &mgr->payload_mask);
    				} else {
    					clear_bit(j + 1, &mgr->payload_mask);
    				}
    			}
    			memset(&mgr->payloads[mgr->max_payloads - 1], 0, sizeof(struct drm_dp_payload));
    			mgr->proposed_vcpis[mgr->max_payloads - 1] = NULL;
    			clear_bit(mgr->max_payloads, &mgr->payload_mask);
    
    		}
    	}
    	mutex_unlock(&mgr->payload_lock);
    
    	return 0;
    }
    EXPORT_SYMBOL(drm_dp_update_payload_part1);
    
    /**
     * drm_dp_update_payload_part2() - Execute payload update part 2
     * @mgr: manager to use.
     *
     * This iterates over all proposed virtual channels, and tries to
     * allocate space in the link for them. For 0->slots transitions,
     * this step writes the remote VC payload commands. For slots->0
     * this just resets some internal state.
     */
    int drm_dp_update_payload_part2(struct drm_dp_mst_topology_mgr *mgr)
    {
    	struct drm_dp_mst_port *port;
    	int i;
    	int ret = 0;
    	mutex_lock(&mgr->payload_lock);
    	for (i = 0; i < mgr->max_payloads; i++) {
    
    		if (!mgr->proposed_vcpis[i])
    			continue;
    
    		port = container_of(mgr->proposed_vcpis[i], struct drm_dp_mst_port, vcpi);
    
    		DRM_DEBUG_KMS("payload %d %d\n", i, mgr->payloads[i].payload_state);
    		if (mgr->payloads[i].payload_state == DP_PAYLOAD_LOCAL) {
    			ret = drm_dp_create_payload_step2(mgr, port, mgr->proposed_vcpis[i]->vcpi, &mgr->payloads[i]);
    		} else if (mgr->payloads[i].payload_state == DP_PAYLOAD_DELETE_LOCAL) {
    			ret = drm_dp_destroy_payload_step2(mgr, mgr->proposed_vcpis[i]->vcpi, &mgr->payloads[i]);
    		}
    		if (ret) {
    			mutex_unlock(&mgr->payload_lock);
    			return ret;
    		}
    	}
    	mutex_unlock(&mgr->payload_lock);
    	return 0;
    }
    EXPORT_SYMBOL(drm_dp_update_payload_part2);
    
    #if 0 /* unused as of yet */
    static int drm_dp_send_dpcd_read(struct drm_dp_mst_topology_mgr *mgr,
    				 struct drm_dp_mst_port *port,
    				 int offset, int size)
    {
    	int len;
    	struct drm_dp_sideband_msg_tx *txmsg;
    
    	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
    	if (!txmsg)
    		return -ENOMEM;
    
    	len = build_dpcd_read(txmsg, port->port_num, 0, 8);
    	txmsg->dst = port->parent;
    
    	drm_dp_queue_down_tx(mgr, txmsg);
    
    	return 0;
    }
    #endif
    
    static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
    				  struct drm_dp_mst_port *port,
    				  int offset, int size, u8 *bytes)
    {
    	int len;
    	int ret;
    	struct drm_dp_sideband_msg_tx *txmsg;
    	struct drm_dp_mst_branch *mstb;
    
    	mstb = drm_dp_get_validated_mstb_ref(mgr, port->parent);
    	if (!mstb)
    		return -EINVAL;
    
    	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
    	if (!txmsg) {
    		ret = -ENOMEM;
    		goto fail_put;
    	}
    
    	len = build_dpcd_write(txmsg, port->port_num, offset, size, bytes);
    	txmsg->dst = mstb;
    
    	drm_dp_queue_down_tx(mgr, txmsg);
    
    	ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
    	if (ret > 0) {
    		if (txmsg->reply.reply_type == 1) {
    			ret = -EINVAL;
    		} else
    			ret = 0;
    	}
    	kfree(txmsg);
    fail_put:
    	drm_dp_put_mst_branch_device(mstb);
    	return ret;
    }
    
    static int drm_dp_encode_up_ack_reply(struct drm_dp_sideband_msg_tx *msg, u8 req_type)
    {
    	struct drm_dp_sideband_msg_reply_body reply;
    
    	reply.reply_type = 0;
    	reply.req_type = req_type;
    	drm_dp_encode_sideband_reply(&reply, msg);
    	return 0;
    }
    
    static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr,
    				    struct drm_dp_mst_branch *mstb,
    				    int req_type, int seqno, bool broadcast)
    {
    	struct drm_dp_sideband_msg_tx *txmsg;
    
    	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
    	if (!txmsg)
    		return -ENOMEM;
    
    	txmsg->dst = mstb;
    	txmsg->seqno = seqno;
    	drm_dp_encode_up_ack_reply(txmsg, req_type);
    
    	mutex_lock(&mgr->qlock);
    
    	process_single_up_tx_qlock(mgr, txmsg);
    
    	mutex_unlock(&mgr->qlock);
    
    	kfree(txmsg);
    	return 0;
    }
    
    static bool drm_dp_get_vc_payload_bw(int dp_link_bw,
    				     int dp_link_count,
    				     int *out)
    {
    	switch (dp_link_bw) {
    	default:
    		DRM_DEBUG_KMS("invalid link bandwidth in DPCD: %x (link count: %d)\n",
    			      dp_link_bw, dp_link_count);
    		return false;
    
    	case DP_LINK_BW_1_62:
    		*out = 3 * dp_link_count;
    		break;
    	case DP_LINK_BW_2_7:
    		*out = 5 * dp_link_count;
    		break;
    	case DP_LINK_BW_5_4:
    		*out = 10 * dp_link_count;
    		break;
    	}
    	return true;
    }
    
    /**
     * drm_dp_mst_topology_mgr_set_mst() - Set the MST state for a topology manager
     * @mgr: manager to set state for
     * @mst_state: true to enable MST on this connector - false to disable.
     *
     * This is called by the driver when it detects an MST capable device plugged
     * into a DP MST capable port, or when a DP MST capable device is unplugged.
     */
    int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool mst_state)
    {
    	int ret = 0;
    	struct drm_dp_mst_branch *mstb = NULL;
    
    	mutex_lock(&mgr->lock);
    	if (mst_state == mgr->mst_state)
    		goto out_unlock;
    
    	mgr->mst_state = mst_state;
    	/* set the device into MST mode */
    	if (mst_state) {
    		WARN_ON(mgr->mst_primary);
    
    		/* get dpcd info */
    		ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, DP_RECEIVER_CAP_SIZE);
    		if (ret != DP_RECEIVER_CAP_SIZE) {
    			DRM_DEBUG_KMS("failed to read DPCD\n");
    			goto out_unlock;
    		}
    
    		if (!drm_dp_get_vc_payload_bw(mgr->dpcd[1],
    					      mgr->dpcd[2] & DP_MAX_LANE_COUNT_MASK,
    					      &mgr->pbn_div)) {
    			ret = -EINVAL;
    			goto out_unlock;
    		}
    
    		mgr->total_pbn = 2560;
    		mgr->total_slots = DIV_ROUND_UP(mgr->total_pbn, mgr->pbn_div);
    		mgr->avail_slots = mgr->total_slots;
    
    		/* add initial branch device at LCT 1 */
    		mstb = drm_dp_add_mst_branch_device(1, NULL);
    		if (mstb == NULL) {
    			ret = -ENOMEM;
    			goto out_unlock;
    		}
    		mstb->mgr = mgr;
    
    		/* give this the main reference */
    		mgr->mst_primary = mstb;
    		kref_get(&mgr->mst_primary->kref);
    
    		{
    			struct drm_dp_payload reset_pay;
    			reset_pay.start_slot = 0;
    			reset_pay.num_slots = 0x3f;
    			drm_dp_dpcd_write_payload(mgr, 0, &reset_pay);
    		}
    
    		ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
    					 DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC);
    		if (ret < 0) {
    			goto out_unlock;
    		}
    
    
    		/* sort out guid */
    		ret = drm_dp_dpcd_read(mgr->aux, DP_GUID, mgr->guid, 16);
    		if (ret != 16) {
    			DRM_DEBUG_KMS("failed to read DP GUID %d\n", ret);
    			goto out_unlock;
    		}
    
    		mgr->guid_valid = drm_dp_validate_guid(mgr, mgr->guid);
    		if (!mgr->guid_valid) {
    			ret = drm_dp_dpcd_write(mgr->aux, DP_GUID, mgr->guid, 16);
    			mgr->guid_valid = true;
    		}
    
    		queue_work(system_long_wq, &mgr->work);
    
    		ret = 0;
    	} else {
    		/* disable MST on the device */
    		mstb = mgr->mst_primary;
    		mgr->mst_primary = NULL;
    		/* this can fail if the device is gone */
    		drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, 0);
    		ret = 0;
    		memset(mgr->payloads, 0, mgr->max_payloads * sizeof(struct drm_dp_payload));
    		mgr->payload_mask = 0;
    		set_bit(0, &mgr->payload_mask);
    		mgr->vcpi_mask = 0;
    	}
    
    out_unlock:
    	mutex_unlock(&mgr->lock);
    	if (mstb)
    		drm_dp_put_mst_branch_device(mstb);
    	return ret;
    
    }
    EXPORT_SYMBOL(drm_dp_mst_topology_mgr_set_mst);
    
    /**
     * drm_dp_mst_topology_mgr_suspend() - suspend the MST manager
     * @mgr: manager to suspend
     *
     * This function tells the MST device that we can't handle UP messages
     * anymore. This should stop it from sending any since we are suspended.
     */
    void drm_dp_mst_topology_mgr_suspend(struct drm_dp_mst_topology_mgr *mgr)
    {
    	mutex_lock(&mgr->lock);
    	drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
    			   DP_MST_EN | DP_UPSTREAM_IS_SRC);
    	mutex_unlock(&mgr->lock);
    	flush_work(&mgr->work);
    	flush_work(&mgr->destroy_connector_work);
    }
    EXPORT_SYMBOL(drm_dp_mst_topology_mgr_suspend);
    
    /**
     * drm_dp_mst_topology_mgr_resume() - resume the MST manager
     * @mgr: manager to resume
     *
     * This will fetch DPCD and see if the device is still there,
     * if it is, it will rewrite the MSTM control bits, and return.
     *
     * if the device fails this returns -1, and the driver should do
     * a full MST reprobe, in case we were undocked.
     */
    int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr)
    {
    	int ret = 0;
    
    	mutex_lock(&mgr->lock);
    
    	if (mgr->mst_primary) {
    		int sret;
    		sret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, DP_RECEIVER_CAP_SIZE);
    		if (sret != DP_RECEIVER_CAP_SIZE) {
    			DRM_DEBUG_KMS("dpcd read failed - undocked during suspend?\n");
    			ret = -1;
    			goto out_unlock;
    		}
    
    		ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
    					 DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC);
    		if (ret < 0) {
    			DRM_DEBUG_KMS("mst write failed - undocked during suspend?\n");
    			ret = -1;
    			goto out_unlock;
    		}
    		ret = 0;
    	} else
    		ret = -1;
    
    out_unlock:
    	mutex_unlock(&mgr->lock);
    	return ret;
    }
    EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume);
    
    static void drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
    {
    	int len;
    	u8 replyblock[32];
    	int replylen, origlen, curreply;
    	int ret;
    	struct drm_dp_sideband_msg_rx *msg;
    	int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE : DP_SIDEBAND_MSG_DOWN_REP_BASE;
    	msg = up ? &mgr->up_req_recv : &mgr->down_rep_recv;
    
    	len = min(mgr->max_dpcd_transaction_bytes, 16);
    	ret = drm_dp_dpcd_read(mgr->aux, basereg,
    			       replyblock, len);
    	if (ret != len) {
    		DRM_DEBUG_KMS("failed to read DPCD down rep %d %d\n", len, ret);
    		return;
    	}
    	ret = drm_dp_sideband_msg_build(msg, replyblock, len, true);
    	if (!ret) {
    		DRM_DEBUG_KMS("sideband msg build failed %d\n", replyblock[0]);
    		return;
    	}
    	replylen = msg->curchunk_len + msg->curchunk_hdrlen;
    
    	origlen = replylen;
    	replylen -= len;
    	curreply = len;
    	while (replylen > 0) {
    		len = min3(replylen, mgr->max_dpcd_transaction_bytes, 16);
    		ret = drm_dp_dpcd_read(mgr->aux, basereg + curreply,
    				    replyblock, len);
    		if (ret != len) {
    			DRM_DEBUG_KMS("failed to read a chunk\n");
    		}
    		ret = drm_dp_sideband_msg_build(msg, replyblock, len, false);
    		if (ret == false)
    			DRM_DEBUG_KMS("failed to build sideband msg\n");
    		curreply += len;
    		replylen -= len;
    	}
    }
    
    static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr)
    {
    	int ret = 0;
    
    	drm_dp_get_one_sb_msg(mgr, false);
    
    	if (mgr->down_rep_recv.have_eomt) {
    		struct drm_dp_sideband_msg_tx *txmsg;
    		struct drm_dp_mst_branch *mstb;
    		int slot = -1;
    		mstb = drm_dp_get_mst_branch_device(mgr,
    						    mgr->down_rep_recv.initial_hdr.lct,
    						    mgr->down_rep_recv.initial_hdr.rad);
    
    		if (!mstb) {
    			DRM_DEBUG_KMS("Got MST reply from unknown device %d\n", mgr->down_rep_recv.initial_hdr.lct);
    			memset(&mgr->down_rep_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
    			return 0;
    		}
    
    		/* find the message */
    		slot = mgr->down_rep_recv.initial_hdr.seqno;
    		mutex_lock(&mgr->qlock);
    		txmsg = mstb->tx_slots[slot];
    		/* remove from slots */
    		mutex_unlock(&mgr->qlock);
    
    		if (!txmsg) {
    			DRM_DEBUG_KMS("Got MST reply with no msg %p %d %d %02x %02x\n",
    			       mstb,
    			       mgr->down_rep_recv.initial_hdr.seqno,
    			       mgr->down_rep_recv.initial_hdr.lct,
    				      mgr->down_rep_recv.initial_hdr.rad[0],
    				      mgr->down_rep_recv.msg[0]);
    			drm_dp_put_mst_branch_device(mstb);
    			memset(&mgr->down_rep_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
    			return 0;
    		}
    
    		drm_dp_sideband_parse_reply(&mgr->down_rep_recv, &txmsg->reply);
    		if (txmsg->reply.reply_type == 1) {
    			DRM_DEBUG_KMS("Got NAK reply: req 0x%02x, reason 0x%02x, nak data 0x%02x\n", txmsg->reply.req_type, txmsg->reply.u.nak.reason, txmsg->reply.u.nak.nak_data);
    		}
    
    		memset(&mgr->down_rep_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
    		drm_dp_put_mst_branch_device(mstb);
    
    		mutex_lock(&mgr->qlock);
    		txmsg->state = DRM_DP_SIDEBAND_TX_RX;
    		mstb->tx_slots[slot] = NULL;
    		mutex_unlock(&mgr->qlock);
    
    		wake_up(&mgr->tx_waitq);
    	}
    	return ret;
    }
    
    static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
    {
    	int ret = 0;
    	drm_dp_get_one_sb_msg(mgr, true);
    
    	if (mgr->up_req_recv.have_eomt) {
    		struct drm_dp_sideband_msg_req_body msg;
    		struct drm_dp_mst_branch *mstb = NULL;
    		bool seqno;
    
    		if (!mgr->up_req_recv.initial_hdr.broadcast) {
    			mstb = drm_dp_get_mst_branch_device(mgr,
    							    mgr->up_req_recv.initial_hdr.lct,
    							    mgr->up_req_recv.initial_hdr.rad);
    			if (!mstb) {
    				DRM_DEBUG_KMS("Got MST reply from unknown device %d\n", mgr->up_req_recv.initial_hdr.lct);
    				memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
    				return 0;
    			}
    		}
    
    		seqno = mgr->up_req_recv.initial_hdr.seqno;
    		drm_dp_sideband_parse_req(&mgr->up_req_recv, &msg);
    
    		if (msg.req_type == DP_CONNECTION_STATUS_NOTIFY) {
    			drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, msg.req_type, seqno, false);
    
    			if (!mstb)
    				mstb = drm_dp_get_mst_branch_device_by_guid(mgr, msg.u.conn_stat.guid);
    
    			if (!mstb) {
    				DRM_DEBUG_KMS("Got MST reply from unknown device %d\n", mgr->up_req_recv.initial_hdr.lct);
    				memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
    				return 0;
    			}
    
    			drm_dp_update_port(mstb, &msg.u.conn_stat);
    			DRM_DEBUG_KMS("Got CSN: pn: %d ldps:%d ddps: %d mcs: %d ip: %d pdt: %d\n", msg.u.conn_stat.port_number, msg.u.conn_stat.legacy_device_plug_status, msg.u.conn_stat.displayport_device_plug_status, msg.u.conn_stat.message_capability_status, msg.u.conn_stat.input_port, msg.u.conn_stat.peer_device_type);
    			(*mgr->cbs->hotplug)(mgr);
    
    		} else if (msg.req_type == DP_RESOURCE_STATUS_NOTIFY) {
    			drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, msg.req_type, seqno, false);
    			if (!mstb)
    				mstb = drm_dp_get_mst_branch_device_by_guid(mgr, msg.u.resource_stat.guid);
    
    			if (!mstb) {
    				DRM_DEBUG_KMS("Got MST reply from unknown device %d\n", mgr->up_req_recv.initial_hdr.lct);
    				memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
    				return 0;
    			}
    
    			DRM_DEBUG_KMS("Got RSN: pn: %d avail_pbn %d\n", msg.u.resource_stat.port_number, msg.u.resource_stat.available_pbn);
    		}
    
    		drm_dp_put_mst_branch_device(mstb);
    		memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
    	}
    	return ret;
    }
    
    /**
     * drm_dp_mst_hpd_irq() - MST hotplug IRQ notify
     * @mgr: manager to notify irq for.
     * @esi: 4 bytes from SINK_COUNT_ESI
     * @handled: whether the hpd interrupt was consumed or not
     *
     * This should be called from the driver when it detects a short IRQ,
     * along with the value of the DEVICE_SERVICE_IRQ_VECTOR_ESI0. The
     * topology manager will process the sideband messages received as a result
     * of this.
     */
    int drm_dp_mst_hpd_irq(struct drm_dp_mst_topology_mgr *mgr, u8 *esi, bool *handled)
    {
    	int ret = 0;
    	int sc;
    	*handled = false;
    	sc = esi[0] & 0x3f;
    
    	if (sc != mgr->sink_count) {
    		mgr->sink_count = sc;
    		*handled = true;
    	}
    
    	if (esi[1] & DP_DOWN_REP_MSG_RDY) {
    		ret = drm_dp_mst_handle_down_rep(mgr);
    		*handled = true;
    	}
    
    	if (esi[1] & DP_UP_REQ_MSG_RDY) {
    		ret |= drm_dp_mst_handle_up_req(mgr);
    		*handled = true;
    	}
    
    	drm_dp_mst_kick_tx(mgr);
    	return ret;
    }
    EXPORT_SYMBOL(drm_dp_mst_hpd_irq);
    
    /**
     * drm_dp_mst_detect_port() - get connection status for an MST port
     * @mgr: manager for this port
     * @port: unverified pointer to a port
     *
     * This returns the current connection state for a port. It validates the
     * port pointer still exists so the caller doesn't require a reference
     */
    enum drm_connector_status drm_dp_mst_detect_port(struct drm_connector *connector,
    						 struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
    {
    	enum drm_connector_status status = connector_status_disconnected;
    
    	/* we need to search for the port in the mgr in case its gone */
    	port = drm_dp_get_validated_port_ref(mgr, port);
    	if (!port)
    		return connector_status_disconnected;
    
    	if (!port->ddps)
    		goto out;
    
    	switch (port->pdt) {
    	case DP_PEER_DEVICE_NONE:
    	case DP_PEER_DEVICE_MST_BRANCHING:
    		break;
    
    	case DP_PEER_DEVICE_SST_SINK:
    		status = connector_status_connected;
    		/* for logical ports - cache the EDID */
    		if (port->port_num >= 8 && !port->cached_edid) {
    			port->cached_edid = drm_get_edid(connector, &port->aux.ddc);
    		}
    		break;
    	case DP_PEER_DEVICE_DP_LEGACY_CONV:
    		if (port->ldps)
    			status = connector_status_connected;
    		break;
    	}
    out:
    	drm_dp_put_port(port);
    	return status;
    }
    EXPORT_SYMBOL(drm_dp_mst_detect_port);
    
    /**
     * drm_dp_mst_port_has_audio() - Check whether port has audio capability or not
     * @mgr: manager for this port
     * @port: unverified pointer to a port.
     *
     * This returns whether the port supports audio or not.
     */
    bool drm_dp_mst_port_has_audio(struct drm_dp_mst_topology_mgr *mgr,
    					struct drm_dp_mst_port *port)
    {
    	bool ret = false;
    
    	port = drm_dp_get_validated_port_ref(mgr, port);
    	if (!port)
    		return ret;
    	ret = port->has_audio;
    	drm_dp_put_port(port);
    	return ret;
    }
    EXPORT_SYMBOL(drm_dp_mst_port_has_audio);
    
    /**
     * drm_dp_mst_get_edid() - get EDID for an MST port
     * @connector: toplevel connector to get EDID for
     * @mgr: manager for this port
     * @port: unverified pointer to a port.
     *
     * This returns an EDID for the port connected to a connector,
     * It validates the pointer still exists so the caller doesn't require a
     * reference.
     */
    struct edid *drm_dp_mst_get_edid(struct drm_connector *connector, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
    {
    	struct edid *edid = NULL;
    
    	/* we need to search for the port in the mgr in case its gone */
    	port = drm_dp_get_validated_port_ref(mgr, port);
    	if (!port)
    		return NULL;
    
    	if (port->cached_edid)
    		edid = drm_edid_duplicate(port->cached_edid);
    	else {
    		edid = drm_get_edid(connector, &port->aux.ddc);
    		drm_mode_connector_set_tile_property(connector);
    	}
    	port->has_audio = drm_detect_monitor_audio(edid);
    	drm_dp_put_port(port);
    	return edid;
    }
    EXPORT_SYMBOL(drm_dp_mst_get_edid);
    
    /**
     * drm_dp_find_vcpi_slots() - find slots for this PBN value
     * @mgr: manager to use
     * @pbn: payload bandwidth to convert into slots.
     */
    int drm_dp_find_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr,
    			   int pbn)
    {
    	int num_slots;
    
    	num_slots = DIV_ROUND_UP(pbn, mgr->pbn_div);
    
    	if (num_slots > mgr->avail_slots)
    		return -ENOSPC;
    	return num_slots;
    }
    EXPORT_SYMBOL(drm_dp_find_vcpi_slots);
    
    static int drm_dp_init_vcpi(struct drm_dp_mst_topology_mgr *mgr,
    			    struct drm_dp_vcpi *vcpi, int pbn)
    {
    	int num_slots;
    	int ret;
    
    	num_slots = DIV_ROUND_UP(pbn, mgr->pbn_div);
    
    	if (num_slots > mgr->avail_slots)
    		return -ENOSPC;
    
    	vcpi->pbn = pbn;
    	vcpi->aligned_pbn = num_slots * mgr->pbn_div;
    	vcpi->num_slots = num_slots;
    
    	ret = drm_dp_mst_assign_payload_id(mgr, vcpi);
    	if (ret < 0)
    		return ret;
    	return 0;
    }
    
    /**
     * drm_dp_mst_allocate_vcpi() - Allocate a virtual channel
     * @mgr: manager for this port
     * @port: port to allocate a virtual channel for.
     * @pbn: payload bandwidth number to request
     * @slots: returned number of slots for this PBN.
     */
    bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port, int pbn, int *slots)
    {
    	int ret;
    
    	port = drm_dp_get_validated_port_ref(mgr, port);
    	if (!port)
    		return false;
    
    	if (port->vcpi.vcpi > 0) {
    		DRM_DEBUG_KMS("payload: vcpi %d already allocated for pbn %d - requested pbn %d\n", port->vcpi.vcpi, port->vcpi.pbn, pbn);
    		if (pbn == port->vcpi.pbn) {
    			*slots = port->vcpi.num_slots;
    			drm_dp_put_port(port);
    			return true;
    		}
    	}
    
    	ret = drm_dp_init_vcpi(mgr, &port->vcpi, pbn);
    	if (ret) {
    		DRM_DEBUG_KMS("failed to init vcpi %d %d %d\n", DIV_ROUND_UP(pbn, mgr->pbn_div), mgr->avail_slots, ret);
    		goto out;
    	}
    	DRM_DEBUG_KMS("initing vcpi for %d %d\n", pbn, port->vcpi.num_slots);
    	*slots = port->vcpi.num_slots;
    
    	drm_dp_put_port(port);
    	return true;
    out:
    	return false;
    }
    EXPORT_SYMBOL(drm_dp_mst_allocate_vcpi);
    
    int drm_dp_mst_get_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
    {
    	int slots = 0;
    	port = drm_dp_get_validated_port_ref(mgr, port);
    	if (!port)
    		return slots;
    
    	slots = port->vcpi.num_slots;
    	drm_dp_put_port(port);
    	return slots;
    }
    EXPORT_SYMBOL(drm_dp_mst_get_vcpi_slots);
    
    /**
     * drm_dp_mst_reset_vcpi_slots() - Reset number of slots to 0 for VCPI
     * @mgr: manager for this port
     * @port: unverified pointer to a port.
     *
     * This just resets the number of slots for the ports VCPI for later programming.
     */
    void drm_dp_mst_reset_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
    {
    	port = drm_dp_get_validated_port_ref(mgr, port);
    	if (!port)
    		return;
    	port->vcpi.num_slots = 0;
    	drm_dp_put_port(port);
    }
    EXPORT_SYMBOL(drm_dp_mst_reset_vcpi_slots);
    
    /**
     * drm_dp_mst_deallocate_vcpi() - deallocate a VCPI
     * @mgr: manager for this port
     * @port: unverified port to deallocate vcpi for
     */
    void drm_dp_mst_deallocate_vcpi(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
    {
    	port = drm_dp_get_validated_port_ref(mgr, port);
    	if (!port)
    		return;
    
    	drm_dp_mst_put_payload_id(mgr, port->vcpi.vcpi);
    	port->vcpi.num_slots = 0;
    	port->vcpi.pbn = 0;
    	port->vcpi.aligned_pbn = 0;
    	port->vcpi.vcpi = 0;
    	drm_dp_put_port(port);
    }
    EXPORT_SYMBOL(drm_dp_mst_deallocate_vcpi);
    
    static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr,
    				     int id, struct drm_dp_payload *payload)
    {
    	u8 payload_alloc[3], status;
    	int ret;
    	int retries = 0;
    
    	drm_dp_dpcd_writeb(mgr->aux, DP_PAYLOAD_TABLE_UPDATE_STATUS,
    			   DP_PAYLOAD_TABLE_UPDATED);
    
    	payload_alloc[0] = id;
    	payload_alloc[1] = payload->start_slot;
    	payload_alloc[2] = payload->num_slots;
    
    	ret = drm_dp_dpcd_write(mgr->aux, DP_PAYLOAD_ALLOCATE_SET, payload_alloc, 3);
    	if (ret != 3) {
    		DRM_DEBUG_KMS("failed to write payload allocation %d\n", ret);
    		goto fail;
    	}
    
    retry:
    	ret = drm_dp_dpcd_readb(mgr->aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status);
    	if (ret < 0) {
    		DRM_DEBUG_KMS("failed to read payload table status %d\n", ret);
    		goto fail;
    	}
    
    	if (!(status & DP_PAYLOAD_TABLE_UPDATED)) {
    		retries++;
    		if (retries < 20) {
    			usleep_range(10000, 20000);
    			goto retry;
    		}
    		DRM_DEBUG_KMS("status not set after read payload table status %d\n", status);
    		ret = -EINVAL;
    		goto fail;
    	}
    	ret = 0;
    fail:
    	return ret;
    }
    
    
    /**
     * drm_dp_check_act_status() - Check ACT handled status.
     * @mgr: manager to use
     *
     * Check the payload status bits in the DPCD for ACT handled completion.
     */
    int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr)
    {
    	u8 status;
    	int ret;
    	int count = 0;
    
    	do {
    		ret = drm_dp_dpcd_readb(mgr->aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status);
    
    		if (ret < 0) {
    			DRM_DEBUG_KMS("failed to read payload table status %d\n", ret);
    			goto fail;
    		}
    
    		if (status & DP_PAYLOAD_ACT_HANDLED)
    			break;
    		count++;
    		udelay(100);
    
    	} while (count < 30);
    
    	if (!(status & DP_PAYLOAD_ACT_HANDLED)) {
    		DRM_DEBUG_KMS("failed to get ACT bit %d after %d retries\n", status, count);
    		ret = -EINVAL;
    		goto fail;
    	}
    	return 0;
    fail:
    	return ret;
    }
    EXPORT_SYMBOL(drm_dp_check_act_status);
    
    /**
     * drm_dp_calc_pbn_mode() - Calculate the PBN for a mode.
     * @clock: dot clock for the mode
     * @bpp: bpp for the mode.
     *
     * This uses the formula in the spec to calculate the PBN value for a mode.
     */
    int drm_dp_calc_pbn_mode(int clock, int bpp)
    {
    	fixed20_12 pix_bw;
    	fixed20_12 fbpp;
    	fixed20_12 result;
    	fixed20_12 margin, tmp;
    	u32 res;
    
    	pix_bw.full = dfixed_const(clock);
    	fbpp.full = dfixed_const(bpp);
    	tmp.full = dfixed_const(8);
    	fbpp.full = dfixed_div(fbpp, tmp);
    
    	result.full = dfixed_mul(pix_bw, fbpp);
    	margin.full = dfixed_const(54);
    	tmp.full = dfixed_const(64);
    	margin.full = dfixed_div(margin, tmp);
    	result.full = dfixed_div(result, margin);
    
    	margin.full = dfixed_const(1006);
    	tmp.full = dfixed_const(1000);
    	margin.full = dfixed_div(margin, tmp);
    	result.full = dfixed_mul(result, margin);
    
    	result.full = dfixed_div(result, tmp);
    	result.full = dfixed_ceil(result);
    	res = dfixed_trunc(result);
    	return res;
    }
    EXPORT_SYMBOL(drm_dp_calc_pbn_mode);
    
    static int test_calc_pbn_mode(void)
    {
    	int ret;
    	ret = drm_dp_calc_pbn_mode(154000, 30);
    	if (ret != 689)
    		return -EINVAL;
    	ret = drm_dp_calc_pbn_mode(234000, 30);
    	if (ret != 1047)
    		return -EINVAL;
    	return 0;
    }
    
    /* we want to kick the TX after we've ack the up/down IRQs. */
    static void drm_dp_mst_kick_tx(struct drm_dp_mst_topology_mgr *mgr)
    {
    	queue_work(system_long_wq, &mgr->tx_work);
    }
    
    static void drm_dp_mst_dump_mstb(struct seq_file *m,
    				 struct drm_dp_mst_branch *mstb)
    {
    	struct drm_dp_mst_port *port;
    	int tabs = mstb->lct;
    	char prefix[10];
    	int i;
    
    	for (i = 0; i < tabs; i++)
    		prefix[i] = '\t';
    	prefix[i] = '\0';
    
    	seq_printf(m, "%smst: %p, %d\n", prefix, mstb, mstb->num_ports);
    	list_for_each_entry(port, &mstb->ports, next) {
    		seq_printf(m, "%sport: %d: ddps: %d ldps: %d, sdp: %d/%d, %p, conn: %p\n", prefix, port->port_num, port->ddps, port->ldps, port->num_sdp_streams, port->num_sdp_stream_sinks, port, port->connector);
    		if (port->mstb)
    			drm_dp_mst_dump_mstb(m, port->mstb);
    	}
    }
    
    static bool dump_dp_payload_table(struct drm_dp_mst_topology_mgr *mgr,
    				  char *buf)
    {
    	int ret;
    	int i;
    	for (i = 0; i < 4; i++) {
    		ret = drm_dp_dpcd_read(mgr->aux, DP_PAYLOAD_TABLE_UPDATE_STATUS + (i * 16), &buf[i * 16], 16);
    		if (ret != 16)
    			break;
    	}
    	if (i == 4)
    		return true;
    	return false;
    }
    
    /**
     * drm_dp_mst_dump_topology(): dump topology to seq file.
     * @m: seq_file to dump output to
     * @mgr: manager to dump current topology for.
     *
     * helper to dump MST topology to a seq file for debugfs.
     */
    void drm_dp_mst_dump_topology(struct seq_file *m,
    			      struct drm_dp_mst_topology_mgr *mgr)
    {
    	int i;
    	struct drm_dp_mst_port *port;
    	mutex_lock(&mgr->lock);
    	if (mgr->mst_primary)
    		drm_dp_mst_dump_mstb(m, mgr->mst_primary);
    
    	/* dump VCPIs */
    	mutex_unlock(&mgr->lock);
    
    	mutex_lock(&mgr->payload_lock);
    	seq_printf(m, "vcpi: %lx %lx\n", mgr->payload_mask, mgr->vcpi_mask);
    
    	for (i = 0; i < mgr->max_payloads; i++) {
    		if (mgr->proposed_vcpis[i]) {
    			port = container_of(mgr->proposed_vcpis[i], struct drm_dp_mst_port, vcpi);
    			seq_printf(m, "vcpi %d: %d %d %d\n", i, port->port_num, port->vcpi.vcpi, port->vcpi.num_slots);
    		} else
    			seq_printf(m, "vcpi %d:unsed\n", i);
    	}
    	for (i = 0; i < mgr->max_payloads; i++) {
    		seq_printf(m, "payload %d: %d, %d, %d\n",
    			   i,
    			   mgr->payloads[i].payload_state,
    			   mgr->payloads[i].start_slot,
    			   mgr->payloads[i].num_slots);
    
    
    	}
    	mutex_unlock(&mgr->payload_lock);
    
    	mutex_lock(&mgr->lock);
    	if (mgr->mst_primary) {
    		u8 buf[64];
    		bool bret;
    		int ret;
    		ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, buf, DP_RECEIVER_CAP_SIZE);
    		seq_printf(m, "dpcd: ");
    		for (i = 0; i < DP_RECEIVER_CAP_SIZE; i++)
    			seq_printf(m, "%02x ", buf[i]);
    		seq_printf(m, "\n");
    		ret = drm_dp_dpcd_read(mgr->aux, DP_FAUX_CAP, buf, 2);
    		seq_printf(m, "faux/mst: ");
    		for (i = 0; i < 2; i++)
    			seq_printf(m, "%02x ", buf[i]);
    		seq_printf(m, "\n");
    		ret = drm_dp_dpcd_read(mgr->aux, DP_MSTM_CTRL, buf, 1);
    		seq_printf(m, "mst ctrl: ");
    		for (i = 0; i < 1; i++)
    			seq_printf(m, "%02x ", buf[i]);
    		seq_printf(m, "\n");
    
    		/* dump the standard OUI branch header */
    		ret = drm_dp_dpcd_read(mgr->aux, DP_BRANCH_OUI, buf, DP_BRANCH_OUI_HEADER_SIZE);
    		seq_printf(m, "branch oui: ");
    		for (i = 0; i < 0x3; i++)
    			seq_printf(m, "%02x", buf[i]);
    		seq_printf(m, " devid: ");
    		for (i = 0x3; i < 0x8; i++)
    			seq_printf(m, "%c", buf[i]);
    		seq_printf(m, " revision: hw: %x.%x sw: %x.%x", buf[0x9] >> 4, buf[0x9] & 0xf, buf[0xa], buf[0xb]);
    		seq_printf(m, "\n");
    		bret = dump_dp_payload_table(mgr, buf);
    		if (bret == true) {
    			seq_printf(m, "payload table: ");
    			for (i = 0; i < 63; i++)
    				seq_printf(m, "%02x ", buf[i]);
    			seq_printf(m, "\n");
    		}
    
    	}
    
    	mutex_unlock(&mgr->lock);
    
    }
    EXPORT_SYMBOL(drm_dp_mst_dump_topology);
    
    static void drm_dp_tx_work(struct work_struct *work)
    {
    	struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, tx_work);
    
    	mutex_lock(&mgr->qlock);
    	if (mgr->tx_down_in_progress)
    		process_single_down_tx_qlock(mgr);
    	mutex_unlock(&mgr->qlock);
    }
    
    static void drm_dp_destroy_connector_work(struct work_struct *work)
    {
    	struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, destroy_connector_work);
    	struct drm_dp_mst_port *port;
    	bool send_hotplug = false;
    	/*
    	 * Not a regular list traverse as we have to drop the destroy
    	 * connector lock before destroying the connector, to avoid AB->BA
    	 * ordering between this lock and the config mutex.
    	 */
    	for (;;) {
    		mutex_lock(&mgr->destroy_connector_lock);
    		port = list_first_entry_or_null(&mgr->destroy_connector_list, struct drm_dp_mst_port, next);
    		if (!port) {
    			mutex_unlock(&mgr->destroy_connector_lock);
    			break;
    		}
    		list_del(&port->next);
    		mutex_unlock(&mgr->destroy_connector_lock);
    
    		mgr->cbs->destroy_connector(mgr, port->connector);
    
    		drm_dp_port_teardown_pdt(port, port->pdt);
    
    		if (!port->input && port->vcpi.vcpi > 0)
    			drm_dp_mst_put_payload_id(mgr, port->vcpi.vcpi);
    		kfree(port);
    		send_hotplug = true;
    	}
    	if (send_hotplug)
    		(*mgr->cbs->hotplug)(mgr);
    }
    
    /**
     * drm_dp_mst_topology_mgr_init - initialise a topology manager
     * @mgr: manager struct to initialise
     * @dev: device providing this structure - for i2c addition.
     * @aux: DP helper aux channel to talk to this device
     * @max_dpcd_transaction_bytes: hw specific DPCD transaction limit
     * @max_payloads: maximum number of payloads this GPU can source
     * @conn_base_id: the connector object ID the MST device is connected to.
     *
     * Return 0 for success, or negative error code on failure
     */
    int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
    				 struct device *dev, struct drm_dp_aux *aux,
    				 int max_dpcd_transaction_bytes,
    				 int max_payloads, int conn_base_id)
    {
    	mutex_init(&mgr->lock);
    	mutex_init(&mgr->qlock);
    	mutex_init(&mgr->payload_lock);
    	mutex_init(&mgr->destroy_connector_lock);
    	INIT_LIST_HEAD(&mgr->tx_msg_downq);
    	INIT_LIST_HEAD(&mgr->destroy_connector_list);
    	INIT_WORK(&mgr->work, drm_dp_mst_link_probe_work);
    	INIT_WORK(&mgr->tx_work, drm_dp_tx_work);
    	INIT_WORK(&mgr->destroy_connector_work, drm_dp_destroy_connector_work);
    	init_waitqueue_head(&mgr->tx_waitq);
    	mgr->dev = dev;
    	mgr->aux = aux;
    	mgr->max_dpcd_transaction_bytes = max_dpcd_transaction_bytes;
    	mgr->max_payloads = max_payloads;
    	mgr->conn_base_id = conn_base_id;
    	mgr->payloads = kcalloc(max_payloads, sizeof(struct drm_dp_payload), GFP_KERNEL);
    	if (!mgr->payloads)
    		return -ENOMEM;
    	mgr->proposed_vcpis = kcalloc(max_payloads, sizeof(struct drm_dp_vcpi *), GFP_KERNEL);
    	if (!mgr->proposed_vcpis)
    		return -ENOMEM;
    	set_bit(0, &mgr->payload_mask);
    	test_calc_pbn_mode();
    	return 0;
    }
    EXPORT_SYMBOL(drm_dp_mst_topology_mgr_init);
    
    /**
     * drm_dp_mst_topology_mgr_destroy() - destroy topology manager.
     * @mgr: manager to destroy
     */
    void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr)
    {
    	flush_work(&mgr->work);
    	flush_work(&mgr->destroy_connector_work);
    	mutex_lock(&mgr->payload_lock);
    	kfree(mgr->payloads);
    	mgr->payloads = NULL;
    	kfree(mgr->proposed_vcpis);
    	mgr->proposed_vcpis = NULL;
    	mutex_unlock(&mgr->payload_lock);
    	mgr->dev = NULL;
    	mgr->aux = NULL;
    }
    EXPORT_SYMBOL(drm_dp_mst_topology_mgr_destroy);
    
    /* I2C device */
    static int drm_dp_mst_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
    			       int num)
    {
    	struct drm_dp_aux *aux = adapter->algo_data;
    	struct drm_dp_mst_port *port = container_of(aux, struct drm_dp_mst_port, aux);
    	struct drm_dp_mst_branch *mstb;
    	struct drm_dp_mst_topology_mgr *mgr = port->mgr;
    	unsigned int i;
    	bool reading = false;
    	struct drm_dp_sideband_msg_req_body msg;
    	struct drm_dp_sideband_msg_tx *txmsg = NULL;
    	int ret;
    
    	mstb = drm_dp_get_validated_mstb_ref(mgr, port->parent);
    	if (!mstb)
    		return -EREMOTEIO;
    
    	/* construct i2c msg */
    	/* see if last msg is a read */
    	if (msgs[num - 1].flags & I2C_M_RD)
    		reading = true;
    
    	if (!reading || (num - 1 > DP_REMOTE_I2C_READ_MAX_TRANSACTIONS)) {
    		DRM_DEBUG_KMS("Unsupported I2C transaction for MST device\n");
    		ret = -EIO;
    		goto out;
    	}
    
    	memset(&msg, 0, sizeof(msg));
    	msg.req_type = DP_REMOTE_I2C_READ;
    	msg.u.i2c_read.num_transactions = num - 1;
    	msg.u.i2c_read.port_number = port->port_num;
    	for (i = 0; i < num - 1; i++) {
    		msg.u.i2c_read.transactions[i].i2c_dev_id = msgs[i].addr;
    		msg.u.i2c_read.transactions[i].num_bytes = msgs[i].len;
    		msg.u.i2c_read.transactions[i].bytes = msgs[i].buf;
    	}
    	msg.u.i2c_read.read_i2c_device_id = msgs[num - 1].addr;
    	msg.u.i2c_read.num_bytes_read = msgs[num - 1].len;
    
    	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
    	if (!txmsg) {
    		ret = -ENOMEM;
    		goto out;
    	}
    
    	txmsg->dst = mstb;
    	drm_dp_encode_sideband_req(&msg, txmsg);
    
    	drm_dp_queue_down_tx(mgr, txmsg);
    
    	ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
    	if (ret > 0) {
    
    		if (txmsg->reply.reply_type == 1) { /* got a NAK back */
    			ret = -EREMOTEIO;
    			goto out;
    		}
    		if (txmsg->reply.u.remote_i2c_read_ack.num_bytes != msgs[num - 1].len) {
    			ret = -EIO;
    			goto out;
    		}
    		memcpy(msgs[num - 1].buf, txmsg->reply.u.remote_i2c_read_ack.bytes, msgs[num - 1].len);
    		ret = num;
    	}
    out:
    	kfree(txmsg);
    	drm_dp_put_mst_branch_device(mstb);
    	return ret;
    }
    
    static u32 drm_dp_mst_i2c_functionality(struct i2c_adapter *adapter)
    {
    	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
    	       I2C_FUNC_SMBUS_READ_BLOCK_DATA |
    	       I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
    	       I2C_FUNC_10BIT_ADDR;
    }
    
    static const struct i2c_algorithm drm_dp_mst_i2c_algo = {
    	.functionality = drm_dp_mst_i2c_functionality,
    	.master_xfer = drm_dp_mst_i2c_xfer,
    };
    
    /**
     * drm_dp_mst_register_i2c_bus() - register an I2C adapter for I2C-over-AUX
     * @aux: DisplayPort AUX channel
     *
     * Returns 0 on success or a negative error code on failure.
     */
    static int drm_dp_mst_register_i2c_bus(struct drm_dp_aux *aux)
    {
    	aux->ddc.algo = &drm_dp_mst_i2c_algo;
    	aux->ddc.algo_data = aux;
    	aux->ddc.retries = 3;
    
    	aux->ddc.class = I2C_CLASS_DDC;
    	aux->ddc.owner = THIS_MODULE;
    	aux->ddc.dev.parent = aux->dev;
    	aux->ddc.dev.of_node = aux->dev->of_node;
    
    	strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev),
    		sizeof(aux->ddc.name));
    
    	return i2c_add_adapter(&aux->ddc);
    }
    
    /**
     * drm_dp_mst_unregister_i2c_bus() - unregister an I2C-over-AUX adapter
     * @aux: DisplayPort AUX channel
     */
    static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_aux *aux)
    {
    	i2c_del_adapter(&aux->ddc);
    }