diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 40ccac61137e27f936128d037e1fe4c52dc721fd..22ce801e3a8d94ca0db6e21289a0c475df7437d5 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -613,6 +613,27 @@ Some of these date from the very introduction of KMS in 2008 ...
Level: Intermediate
+Remove automatic page mapping from dma-buf importing
+----------------------------------------------------
+
+When importing dma-bufs, the dma-buf and PRIME frameworks automatically map
+imported pages into the importer's DMA area. drm_gem_prime_fd_to_handle() and
+drm_gem_prime_handle_to_fd() require that importers call dma_buf_attach()
+even if they never do actual device DMA, but only CPU access through
+dma_buf_vmap(). This is a problem for USB devices, which do not support DMA
+operations.
+
+To fix the issue, automatic page mappings should be removed from the
+buffer-sharing code. Fixing this is a bit more involved, since the import/export
+cache is also tied to &drm_gem_object.import_attach. Meanwhile we paper over
+this problem for USB devices by fishing out the USB host controller device, as
+long as that supports DMA. Otherwise importing can still needlessly fail.
+
+Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter
+
+Level: Advanced
+
+
Better Testing
==============
diff --git a/drivers/gpu/drm/tiny/gm12u320.c b/drivers/gpu/drm/tiny/gm12u320.c
index 33f65f4626e5a3cb2e66722aa20a36300d0044d7..23866a54e3f919ec89af46e365c31dceb15f177d 100644
--- a/drivers/gpu/drm/tiny/gm12u320.c
+++ b/drivers/gpu/drm/tiny/gm12u320.c
@@ -83,6 +83,7 @@ MODULE_PARM_DESC(eco_mode, "Turn on Eco mode (less bright, more silent)");
struct gm12u320_device {
struct drm_device dev;
+ struct device *dmadev;
struct drm_simple_display_pipe pipe;
struct drm_connector conn;
unsigned char *cmd_buf;
@@ -601,6 +602,22 @@ static const uint64_t gm12u320_pipe_modifiers[] = {
DRM_FORMAT_MOD_INVALID
};
+/*
+ * FIXME: Dma-buf sharing requires DMA support by the importing device.
+ * This function is a workaround to make USB devices work as well.
+ * See todo.rst for how to fix the issue in the dma-buf framework.
+ */
+static struct drm_gem_object *gm12u320_gem_prime_import(struct drm_device *dev,
+ struct dma_buf *dma_buf)
+{
+ struct gm12u320_device *gm12u320 = to_gm12u320(dev);
+
+ if (!gm12u320->dmadev)
+ return ERR_PTR(-ENODEV);
+
+ return drm_gem_prime_import_dev(dev, dma_buf, gm12u320->dmadev);
+}
+
DEFINE_DRM_GEM_FOPS(gm12u320_fops);
static const struct drm_driver gm12u320_drm_driver = {
@@ -614,6 +631,7 @@ static const struct drm_driver gm12u320_drm_driver = {
.fops = &gm12u320_fops,
DRM_GEM_SHMEM_DRIVER_OPS,
+ .gem_prime_import = gm12u320_gem_prime_import,
};
static const struct drm_mode_config_funcs gm12u320_mode_config_funcs = {
@@ -640,15 +658,18 @@ static int gm12u320_usb_probe(struct usb_interface *interface,
struct gm12u320_device, dev);
if (IS_ERR(gm12u320))
return PTR_ERR(gm12u320);
+ dev = &gm12u320->dev;
+
+ gm12u320->dmadev = usb_intf_get_dma_device(to_usb_interface(dev->dev));
+ if (!gm12u320->dmadev)
+ drm_warn(dev, "buffer sharing not supported"); /* not an error */
INIT_DELAYED_WORK(&gm12u320->fb_update.work, gm12u320_fb_update_work);
mutex_init(&gm12u320->fb_update.lock);
- dev = &gm12u320->dev;
-
ret = drmm_mode_config_init(dev);
if (ret)
- return ret;
+ goto err_put_device;
dev->mode_config.min_width = GM12U320_USER_WIDTH;
dev->mode_config.max_width = GM12U320_USER_WIDTH;
@@ -658,15 +679,15 @@ static int gm12u320_usb_probe(struct usb_interface *interface,
ret = gm12u320_usb_alloc(gm12u320);
if (ret)
- return ret;
+ goto err_put_device;
ret = gm12u320_set_ecomode(gm12u320);
if (ret)
- return ret;
+ goto err_put_device;
ret = gm12u320_conn_init(gm12u320);
if (ret)
- return ret;
+ goto err_put_device;
ret = drm_simple_display_pipe_init(&gm12u320->dev,
&gm12u320->pipe,
@@ -676,24 +697,31 @@ static int gm12u320_usb_probe(struct usb_interface *interface,
gm12u320_pipe_modifiers,
&gm12u320->conn);
if (ret)
- return ret;
+ goto err_put_device;
drm_mode_config_reset(dev);
usb_set_intfdata(interface, dev);
ret = drm_dev_register(dev, 0);
if (ret)
- return ret;
+ goto err_put_device;
drm_fbdev_generic_setup(dev, 0);
return 0;
+
+err_put_device:
+ put_device(gm12u320->dmadev);
+ return ret;
}
static void gm12u320_usb_disconnect(struct usb_interface *interface)
{
struct drm_device *dev = usb_get_intfdata(interface);
+ struct gm12u320_device *gm12u320 = to_gm12u320(dev);
+ put_device(gm12u320->dmadev);
+ gm12u320->dmadev = NULL;
drm_dev_unplug(dev);
drm_atomic_helper_shutdown(dev);
}
diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c
index 9269092697d8ca4faa574fd93fd05fd6d90ffac4..5703277c6f5276197f1d5a4c5d8d6ae76723456b 100644
--- a/drivers/gpu/drm/udl/udl_drv.c
+++ b/drivers/gpu/drm/udl/udl_drv.c
@@ -32,6 +32,22 @@ static int udl_usb_resume(struct usb_interface *interface)
return drm_mode_config_helper_resume(dev);
}
+/*
+ * FIXME: Dma-buf sharing requires DMA support by the importing device.
+ * This function is a workaround to make USB devices work as well.
+ * See todo.rst for how to fix the issue in the dma-buf framework.
+ */
+static struct drm_gem_object *udl_driver_gem_prime_import(struct drm_device *dev,
+ struct dma_buf *dma_buf)
+{
+ struct udl_device *udl = to_udl(dev);
+
+ if (!udl->dmadev)
+ return ERR_PTR(-ENODEV);
+
+ return drm_gem_prime_import_dev(dev, dma_buf, udl->dmadev);
+}
+
DEFINE_DRM_GEM_FOPS(udl_driver_fops);
static const struct drm_driver driver = {
@@ -40,6 +56,7 @@ static const struct drm_driver driver = {
/* GEM hooks */
.fops = &udl_driver_fops,
DRM_GEM_SHMEM_DRIVER_OPS,
+ .gem_prime_import = udl_driver_gem_prime_import,
.name = DRIVER_NAME,
.desc = DRIVER_DESC,
diff --git a/drivers/gpu/drm/udl/udl_drv.h b/drivers/gpu/drm/udl/udl_drv.h
index 875e73551ae981451501d0b3142bd5e9667ae5f5..cc16a13316e4e1f565331449b6ee17b6cee3b543 100644
--- a/drivers/gpu/drm/udl/udl_drv.h
+++ b/drivers/gpu/drm/udl/udl_drv.h
@@ -50,6 +50,7 @@ struct urb_list {
struct udl_device {
struct drm_device drm;
struct device *dev;
+ struct device *dmadev;
struct drm_simple_display_pipe display_pipe;
diff --git a/drivers/gpu/drm/udl/udl_main.c b/drivers/gpu/drm/udl/udl_main.c
index 0e2a376cb0752a33a659e7236969571077e12c42..853f147036f6b5c5ecda9598c0bbd8d0f010a8d0 100644
--- a/drivers/gpu/drm/udl/udl_main.c
+++ b/drivers/gpu/drm/udl/udl_main.c
@@ -315,6 +315,10 @@ int udl_init(struct udl_device *udl)
DRM_DEBUG("\n");
+ udl->dmadev = usb_intf_get_dma_device(to_usb_interface(dev->dev));
+ if (!udl->dmadev)
+ drm_warn(dev, "buffer sharing not supported"); /* not an error */
+
mutex_init(&udl->gem_lock);
if (!udl_parse_vendor_descriptor(udl)) {
@@ -343,12 +347,18 @@ int udl_init(struct udl_device *udl)
err:
if (udl->urbs.count)
udl_free_urb_list(dev);
+ put_device(udl->dmadev);
DRM_ERROR("%d\n", ret);
return ret;
}
int udl_drop_usb(struct drm_device *dev)
{
+ struct udl_device *udl = to_udl(dev);
+
udl_free_urb_list(dev);
+ put_device(udl->dmadev);
+ udl->dmadev = NULL;
+
return 0;
}
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 8f07b051610096d3957702c255d44b8183103ef2..a566bb494e246b852578130522539d577f06d256 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -748,6 +748,38 @@ void usb_put_intf(struct usb_interface *intf)
}
EXPORT_SYMBOL_GPL(usb_put_intf);
+/**
+ * usb_intf_get_dma_device - acquire a reference on the usb interface's DMA endpoint
+ * @intf: the usb interface
+ *
+ * While a USB device cannot perform DMA operations by itself, many USB
+ * controllers can. A call to usb_intf_get_dma_device() returns the DMA endpoint
+ * for the given USB interface, if any. The returned device structure must be
+ * released with put_device().
+ *
+ * See also usb_get_dma_device().
+ *
+ * Returns: A reference to the usb interface's DMA endpoint; or NULL if none
+ * exists.
+ */
+struct device *usb_intf_get_dma_device(struct usb_interface *intf)
+{
+ struct usb_device *udev = interface_to_usbdev(intf);
+ struct device *dmadev;
+
+ if (!udev->bus)
+ return NULL;
+
+ dmadev = get_device(udev->bus->sysdev);
+ if (!dmadev || !dmadev->dma_mask) {
+ put_device(dmadev);
+ return NULL;
+ }
+
+ return dmadev;
+}
+EXPORT_SYMBOL_GPL(usb_intf_get_dma_device);
+
/* USB device locking
*
* USB devices and interfaces are locked using the semaphore in their
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 7d72c4e0713c1068d11a01256de7a37bc44b809b..d6a41841b93e4f92647e938d0bff02712b795f12 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -746,6 +746,8 @@ extern int usb_lock_device_for_reset(struct usb_device *udev,
extern int usb_reset_device(struct usb_device *dev);
extern void usb_queue_reset_device(struct usb_interface *dev);
+extern struct device *usb_intf_get_dma_device(struct usb_interface *intf);
+
#ifdef CONFIG_ACPI
extern int usb_acpi_set_power_state(struct usb_device *hdev, int index,
bool enable);