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32 results

smp.c

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    • Adrian Bunk's avatar
      81e48073
      m32r/kernel/: cleanups · 81e48073
      Adrian Bunk authored
      
      This patch contains the following cleanups:
      - make the following needlessly global code static:
        - entry.S: resume_userspace
        - process.c: pm_idle
        - process.c: default_idle()
        - smp.c: send_IPI_allbutself()
        - time.c: timer_interrupt()
        - time.c: struct irq0
        - traps.c: set_eit_vector_entries()
        - traps.c: kstack_depth_to_print
        - traps.c: show_trace()
        - traps.c: die_lock
      - remove the following unused code:
        - head.S: startup_32
        - process.c: hlt_counter
        - process.c: disable_hlt()
        - process.c: enable_hlt()
        - process.c: dump_task_regs()
      - remove the following variables and their usages since they were
        always 0:
        - irq.c: irq_err_count
        - irq.c: irq_mis_count
      
      Signed-off-by: default avatarAdrian Bunk <bunk@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarHirokazu Takata <takata@linux-m32r.org>
      81e48073
      History
      m32r/kernel/: cleanups
      Adrian Bunk authored
      
      This patch contains the following cleanups:
      - make the following needlessly global code static:
        - entry.S: resume_userspace
        - process.c: pm_idle
        - process.c: default_idle()
        - smp.c: send_IPI_allbutself()
        - time.c: timer_interrupt()
        - time.c: struct irq0
        - traps.c: set_eit_vector_entries()
        - traps.c: kstack_depth_to_print
        - traps.c: show_trace()
        - traps.c: die_lock
      - remove the following unused code:
        - head.S: startup_32
        - process.c: hlt_counter
        - process.c: disable_hlt()
        - process.c: enable_hlt()
        - process.c: dump_task_regs()
      - remove the following variables and their usages since they were
        always 0:
        - irq.c: irq_err_count
        - irq.c: irq_mis_count
      
      Signed-off-by: default avatarAdrian Bunk <bunk@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarHirokazu Takata <takata@linux-m32r.org>
    debug.c 44.53 KiB
    /*
     * Copyright (C) 2008 Advanced Micro Devices, Inc.
     *
     * Author: Joerg Roedel <joerg.roedel@amd.com>
     *
     * This program is free software; you can redistribute it and/or modify it
     * under the terms of the GNU General Public License version 2 as published
     * by the Free Software Foundation.
     *
     * This program is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     * GNU General Public License for more details.
     *
     * You should have received a copy of the GNU General Public License
     * along with this program; if not, write to the Free Software
     * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
     */
    
    #define pr_fmt(fmt)	"DMA-API: " fmt
    
    #include <linux/sched/task_stack.h>
    #include <linux/scatterlist.h>
    #include <linux/dma-mapping.h>
    #include <linux/sched/task.h>
    #include <linux/stacktrace.h>
    #include <linux/dma-debug.h>
    #include <linux/spinlock.h>
    #include <linux/vmalloc.h>
    #include <linux/debugfs.h>
    #include <linux/uaccess.h>
    #include <linux/export.h>
    #include <linux/device.h>
    #include <linux/types.h>
    #include <linux/sched.h>
    #include <linux/ctype.h>
    #include <linux/list.h>
    #include <linux/slab.h>
    
    #include <asm/sections.h>
    
    #define HASH_SIZE       1024ULL
    #define HASH_FN_SHIFT   13
    #define HASH_FN_MASK    (HASH_SIZE - 1)
    
    #define PREALLOC_DMA_DEBUG_ENTRIES (1 << 16)
    /* If the pool runs out, add this many new entries at once */
    #define DMA_DEBUG_DYNAMIC_ENTRIES (PAGE_SIZE / sizeof(struct dma_debug_entry))
    
    enum {
    	dma_debug_single,
    	dma_debug_sg,
    	dma_debug_coherent,
    	dma_debug_resource,
    };
    
    enum map_err_types {
    	MAP_ERR_CHECK_NOT_APPLICABLE,
    	MAP_ERR_NOT_CHECKED,
    	MAP_ERR_CHECKED,
    };
    
    #define DMA_DEBUG_STACKTRACE_ENTRIES 5
    
    /**
     * struct dma_debug_entry - track a dma_map* or dma_alloc_coherent mapping
     * @list: node on pre-allocated free_entries list
     * @dev: 'dev' argument to dma_map_{page|single|sg} or dma_alloc_coherent
     * @type: single, page, sg, coherent
     * @pfn: page frame of the start address
     * @offset: offset of mapping relative to pfn
     * @size: length of the mapping
     * @direction: enum dma_data_direction
     * @sg_call_ents: 'nents' from dma_map_sg
     * @sg_mapped_ents: 'mapped_ents' from dma_map_sg
     * @map_err_type: track whether dma_mapping_error() was checked
     * @stacktrace: support backtraces when a violation is detected
     */
    struct dma_debug_entry {
    	struct list_head list;
    	struct device    *dev;
    	int              type;
    	unsigned long	 pfn;
    	size_t		 offset;
    	u64              dev_addr;
    	u64              size;
    	int              direction;
    	int		 sg_call_ents;
    	int		 sg_mapped_ents;
    	enum map_err_types  map_err_type;
    #ifdef CONFIG_STACKTRACE
    	struct		 stack_trace stacktrace;
    	unsigned long	 st_entries[DMA_DEBUG_STACKTRACE_ENTRIES];
    #endif
    };
    
    typedef bool (*match_fn)(struct dma_debug_entry *, struct dma_debug_entry *);
    
    struct hash_bucket {
    	struct list_head list;
    	spinlock_t lock;
    } ____cacheline_aligned_in_smp;
    
    /* Hash list to save the allocated dma addresses */
    static struct hash_bucket dma_entry_hash[HASH_SIZE];
    /* List of pre-allocated dma_debug_entry's */
    static LIST_HEAD(free_entries);
    /* Lock for the list above */
    static DEFINE_SPINLOCK(free_entries_lock);
    
    /* Global disable flag - will be set in case of an error */
    static bool global_disable __read_mostly;
    
    /* Early initialization disable flag, set at the end of dma_debug_init */
    static bool dma_debug_initialized __read_mostly;
    
    static inline bool dma_debug_disabled(void)
    {
    	return global_disable || !dma_debug_initialized;
    }
    
    /* Global error count */
    static u32 error_count;
    
    /* Global error show enable*/
    static u32 show_all_errors __read_mostly;
    /* Number of errors to show */
    static u32 show_num_errors = 1;
    
    static u32 num_free_entries;
    static u32 min_free_entries;
    static u32 nr_total_entries;
    
    /* number of preallocated entries requested by kernel cmdline */
    static u32 nr_prealloc_entries = PREALLOC_DMA_DEBUG_ENTRIES;
    
    /* debugfs dentry's for the stuff above */
    static struct dentry *dma_debug_dent        __read_mostly;
    static struct dentry *global_disable_dent   __read_mostly;
    static struct dentry *error_count_dent      __read_mostly;
    static struct dentry *show_all_errors_dent  __read_mostly;
    static struct dentry *show_num_errors_dent  __read_mostly;
    static struct dentry *num_free_entries_dent __read_mostly;
    static struct dentry *min_free_entries_dent __read_mostly;
    static struct dentry *nr_total_entries_dent __read_mostly;
    static struct dentry *filter_dent           __read_mostly;
    
    /* per-driver filter related state */
    
    #define NAME_MAX_LEN	64
    
    static char                  current_driver_name[NAME_MAX_LEN] __read_mostly;
    static struct device_driver *current_driver                    __read_mostly;
    
    static DEFINE_RWLOCK(driver_name_lock);
    
    static const char *const maperr2str[] = {
    	[MAP_ERR_CHECK_NOT_APPLICABLE] = "dma map error check not applicable",
    	[MAP_ERR_NOT_CHECKED] = "dma map error not checked",
    	[MAP_ERR_CHECKED] = "dma map error checked",
    };
    
    static const char *type2name[5] = { "single", "page",
    				    "scather-gather", "coherent",
    				    "resource" };
    
    static const char *dir2name[4] = { "DMA_BIDIRECTIONAL", "DMA_TO_DEVICE",
    				   "DMA_FROM_DEVICE", "DMA_NONE" };
    
    /*
     * The access to some variables in this macro is racy. We can't use atomic_t
     * here because all these variables are exported to debugfs. Some of them even
     * writeable. This is also the reason why a lock won't help much. But anyway,
     * the races are no big deal. Here is why:
     *
     *   error_count: the addition is racy, but the worst thing that can happen is
     *                that we don't count some errors
     *   show_num_errors: the subtraction is racy. Also no big deal because in
     *                    worst case this will result in one warning more in the
     *                    system log than the user configured. This variable is
     *                    writeable via debugfs.
     */
    static inline void dump_entry_trace(struct dma_debug_entry *entry)
    {
    #ifdef CONFIG_STACKTRACE
    	if (entry) {
    		pr_warning("Mapped at:\n");
    		print_stack_trace(&entry->stacktrace, 0);
    	}
    #endif
    }
    
    static bool driver_filter(struct device *dev)
    {
    	struct device_driver *drv;
    	unsigned long flags;
    	bool ret;
    
    	/* driver filter off */
    	if (likely(!current_driver_name[0]))
    		return true;
    
    	/* driver filter on and initialized */
    	if (current_driver && dev && dev->driver == current_driver)
    		return true;
    
    	/* driver filter on, but we can't filter on a NULL device... */
    	if (!dev)
    		return false;
    
    	if (current_driver || !current_driver_name[0])
    		return false;
    
    	/* driver filter on but not yet initialized */
    	drv = dev->driver;
    	if (!drv)
    		return false;
    
    	/* lock to protect against change of current_driver_name */
    	read_lock_irqsave(&driver_name_lock, flags);
    
    	ret = false;
    	if (drv->name &&
    	    strncmp(current_driver_name, drv->name, NAME_MAX_LEN - 1) == 0) {
    		current_driver = drv;
    		ret = true;
    	}
    
    	read_unlock_irqrestore(&driver_name_lock, flags);
    
    	return ret;
    }
    
    #define err_printk(dev, entry, format, arg...) do {			\
    		error_count += 1;					\
    		if (driver_filter(dev) &&				\
    		    (show_all_errors || show_num_errors > 0)) {		\
    			WARN(1, pr_fmt("%s %s: ") format,		\
    			     dev ? dev_driver_string(dev) : "NULL",	\
    			     dev ? dev_name(dev) : "NULL", ## arg);	\
    			dump_entry_trace(entry);			\
    		}							\
    		if (!show_all_errors && show_num_errors > 0)		\
    			show_num_errors -= 1;				\
    	} while (0);
    
    /*
     * Hash related functions
     *
     * Every DMA-API request is saved into a struct dma_debug_entry. To
     * have quick access to these structs they are stored into a hash.
     */
    static int hash_fn(struct dma_debug_entry *entry)
    {
    	/*
    	 * Hash function is based on the dma address.
    	 * We use bits 20-27 here as the index into the hash
    	 */
    	return (entry->dev_addr >> HASH_FN_SHIFT) & HASH_FN_MASK;
    }
    
    /*
     * Request exclusive access to a hash bucket for a given dma_debug_entry.
     */
    static struct hash_bucket *get_hash_bucket(struct dma_debug_entry *entry,
    					   unsigned long *flags)
    	__acquires(&dma_entry_hash[idx].lock)
    {
    	int idx = hash_fn(entry);
    	unsigned long __flags;
    
    	spin_lock_irqsave(&dma_entry_hash[idx].lock, __flags);
    	*flags = __flags;
    	return &dma_entry_hash[idx];
    }
    
    /*
     * Give up exclusive access to the hash bucket
     */
    static void put_hash_bucket(struct hash_bucket *bucket,
    			    unsigned long *flags)
    	__releases(&bucket->lock)
    {
    	unsigned long __flags = *flags;
    
    	spin_unlock_irqrestore(&bucket->lock, __flags);
    }
    
    static bool exact_match(struct dma_debug_entry *a, struct dma_debug_entry *b)
    {
    	return ((a->dev_addr == b->dev_addr) &&
    		(a->dev == b->dev)) ? true : false;
    }
    
    static bool containing_match(struct dma_debug_entry *a,
    			     struct dma_debug_entry *b)
    {
    	if (a->dev != b->dev)
    		return false;
    
    	if ((b->dev_addr <= a->dev_addr) &&
    	    ((b->dev_addr + b->size) >= (a->dev_addr + a->size)))
    		return true;
    
    	return false;
    }
    
    /*
     * Search a given entry in the hash bucket list
     */
    static struct dma_debug_entry *__hash_bucket_find(struct hash_bucket *bucket,
    						  struct dma_debug_entry *ref,
    						  match_fn match)
    {
    	struct dma_debug_entry *entry, *ret = NULL;
    	int matches = 0, match_lvl, last_lvl = -1;
    
    	list_for_each_entry(entry, &bucket->list, list) {
    		if (!match(ref, entry))
    			continue;
    
    		/*
    		 * Some drivers map the same physical address multiple
    		 * times. Without a hardware IOMMU this results in the
    		 * same device addresses being put into the dma-debug
    		 * hash multiple times too. This can result in false
    		 * positives being reported. Therefore we implement a
    		 * best-fit algorithm here which returns the entry from
    		 * the hash which fits best to the reference value
    		 * instead of the first-fit.
    		 */
    		matches += 1;
    		match_lvl = 0;
    		entry->size         == ref->size         ? ++match_lvl : 0;
    		entry->type         == ref->type         ? ++match_lvl : 0;
    		entry->direction    == ref->direction    ? ++match_lvl : 0;
    		entry->sg_call_ents == ref->sg_call_ents ? ++match_lvl : 0;
    
    		if (match_lvl == 4) {
    			/* perfect-fit - return the result */
    			return entry;
    		} else if (match_lvl > last_lvl) {
    			/*
    			 * We found an entry that fits better then the
    			 * previous one or it is the 1st match.
    			 */
    			last_lvl = match_lvl;
    			ret      = entry;
    		}
    	}
    
    	/*
    	 * If we have multiple matches but no perfect-fit, just return
    	 * NULL.
    	 */
    	ret = (matches == 1) ? ret : NULL;
    
    	return ret;
    }
    
    static struct dma_debug_entry *bucket_find_exact(struct hash_bucket *bucket,
    						 struct dma_debug_entry *ref)
    {
    	return __hash_bucket_find(bucket, ref, exact_match);
    }
    
    static struct dma_debug_entry *bucket_find_contain(struct hash_bucket **bucket,
    						   struct dma_debug_entry *ref,
    						   unsigned long *flags)
    {
    
    	unsigned int max_range = dma_get_max_seg_size(ref->dev);
    	struct dma_debug_entry *entry, index = *ref;
    	unsigned int range = 0;
    
    	while (range <= max_range) {
    		entry = __hash_bucket_find(*bucket, ref, containing_match);
    
    		if (entry)
    			return entry;
    
    		/*
    		 * Nothing found, go back a hash bucket
    		 */
    		put_hash_bucket(*bucket, flags);
    		range          += (1 << HASH_FN_SHIFT);
    		index.dev_addr -= (1 << HASH_FN_SHIFT);
    		*bucket = get_hash_bucket(&index, flags);
    	}
    
    	return NULL;
    }
    
    /*
     * Add an entry to a hash bucket
     */
    static void hash_bucket_add(struct hash_bucket *bucket,
    			    struct dma_debug_entry *entry)
    {
    	list_add_tail(&entry->list, &bucket->list);
    }
    
    /*
     * Remove entry from a hash bucket list
     */
    static void hash_bucket_del(struct dma_debug_entry *entry)
    {
    	list_del(&entry->list);
    }
    
    static unsigned long long phys_addr(struct dma_debug_entry *entry)
    {
    	if (entry->type == dma_debug_resource)
    		return __pfn_to_phys(entry->pfn) + entry->offset;
    
    	return page_to_phys(pfn_to_page(entry->pfn)) + entry->offset;
    }
    
    /*
     * Dump mapping entries for debugging purposes
     */
    void debug_dma_dump_mappings(struct device *dev)
    {
    	int idx;
    
    	for (idx = 0; idx < HASH_SIZE; idx++) {
    		struct hash_bucket *bucket = &dma_entry_hash[idx];
    		struct dma_debug_entry *entry;
    		unsigned long flags;
    
    		spin_lock_irqsave(&bucket->lock, flags);
    
    		list_for_each_entry(entry, &bucket->list, list) {
    			if (!dev || dev == entry->dev) {
    				dev_info(entry->dev,
    					 "%s idx %d P=%Lx N=%lx D=%Lx L=%Lx %s %s\n",
    					 type2name[entry->type], idx,
    					 phys_addr(entry), entry->pfn,
    					 entry->dev_addr, entry->size,
    					 dir2name[entry->direction],
    					 maperr2str[entry->map_err_type]);
    			}
    		}
    
    		spin_unlock_irqrestore(&bucket->lock, flags);
    	}
    }
    
    /*
     * For each mapping (initial cacheline in the case of
     * dma_alloc_coherent/dma_map_page, initial cacheline in each page of a
     * scatterlist, or the cacheline specified in dma_map_single) insert
     * into this tree using the cacheline as the key. At
     * dma_unmap_{single|sg|page} or dma_free_coherent delete the entry.  If
     * the entry already exists at insertion time add a tag as a reference
     * count for the overlapping mappings.  For now, the overlap tracking
     * just ensures that 'unmaps' balance 'maps' before marking the
     * cacheline idle, but we should also be flagging overlaps as an API
     * violation.
     *
     * Memory usage is mostly constrained by the maximum number of available
     * dma-debug entries in that we need a free dma_debug_entry before
     * inserting into the tree.  In the case of dma_map_page and
     * dma_alloc_coherent there is only one dma_debug_entry and one
     * dma_active_cacheline entry to track per event.  dma_map_sg(), on the
     * other hand, consumes a single dma_debug_entry, but inserts 'nents'
     * entries into the tree.
     *
     * At any time debug_dma_assert_idle() can be called to trigger a
     * warning if any cachelines in the given page are in the active set.
     */
    static RADIX_TREE(dma_active_cacheline, GFP_NOWAIT);
    static DEFINE_SPINLOCK(radix_lock);
    #define ACTIVE_CACHELINE_MAX_OVERLAP ((1 << RADIX_TREE_MAX_TAGS) - 1)
    #define CACHELINE_PER_PAGE_SHIFT (PAGE_SHIFT - L1_CACHE_SHIFT)
    #define CACHELINES_PER_PAGE (1 << CACHELINE_PER_PAGE_SHIFT)
    
    static phys_addr_t to_cacheline_number(struct dma_debug_entry *entry)
    {
    	return (entry->pfn << CACHELINE_PER_PAGE_SHIFT) +
    		(entry->offset >> L1_CACHE_SHIFT);
    }
    
    static int active_cacheline_read_overlap(phys_addr_t cln)
    {
    	int overlap = 0, i;
    
    	for (i = RADIX_TREE_MAX_TAGS - 1; i >= 0; i--)
    		if (radix_tree_tag_get(&dma_active_cacheline, cln, i))
    			overlap |= 1 << i;
    	return overlap;
    }
    
    static int active_cacheline_set_overlap(phys_addr_t cln, int overlap)
    {
    	int i;
    
    	if (overlap > ACTIVE_CACHELINE_MAX_OVERLAP || overlap < 0)
    		return overlap;
    
    	for (i = RADIX_TREE_MAX_TAGS - 1; i >= 0; i--)
    		if (overlap & 1 << i)
    			radix_tree_tag_set(&dma_active_cacheline, cln, i);
    		else
    			radix_tree_tag_clear(&dma_active_cacheline, cln, i);
    
    	return overlap;
    }
    
    static void active_cacheline_inc_overlap(phys_addr_t cln)
    {
    	int overlap = active_cacheline_read_overlap(cln);
    
    	overlap = active_cacheline_set_overlap(cln, ++overlap);
    
    	/* If we overflowed the overlap counter then we're potentially
    	 * leaking dma-mappings.  Otherwise, if maps and unmaps are
    	 * balanced then this overflow may cause false negatives in
    	 * debug_dma_assert_idle() as the cacheline may be marked idle
    	 * prematurely.
    	 */
    	WARN_ONCE(overlap > ACTIVE_CACHELINE_MAX_OVERLAP,
    		  pr_fmt("exceeded %d overlapping mappings of cacheline %pa\n"),
    		  ACTIVE_CACHELINE_MAX_OVERLAP, &cln);
    }
    
    static int active_cacheline_dec_overlap(phys_addr_t cln)
    {
    	int overlap = active_cacheline_read_overlap(cln);
    
    	return active_cacheline_set_overlap(cln, --overlap);
    }
    
    static int active_cacheline_insert(struct dma_debug_entry *entry)
    {
    	phys_addr_t cln = to_cacheline_number(entry);
    	unsigned long flags;
    	int rc;
    
    	/* If the device is not writing memory then we don't have any
    	 * concerns about the cpu consuming stale data.  This mitigates
    	 * legitimate usages of overlapping mappings.
    	 */
    	if (entry->direction == DMA_TO_DEVICE)
    		return 0;
    
    	spin_lock_irqsave(&radix_lock, flags);
    	rc = radix_tree_insert(&dma_active_cacheline, cln, entry);
    	if (rc == -EEXIST)
    		active_cacheline_inc_overlap(cln);
    	spin_unlock_irqrestore(&radix_lock, flags);
    
    	return rc;
    }
    
    static void active_cacheline_remove(struct dma_debug_entry *entry)
    {
    	phys_addr_t cln = to_cacheline_number(entry);
    	unsigned long flags;
    
    	/* ...mirror the insert case */
    	if (entry->direction == DMA_TO_DEVICE)
    		return;
    
    	spin_lock_irqsave(&radix_lock, flags);
    	/* since we are counting overlaps the final put of the
    	 * cacheline will occur when the overlap count is 0.
    	 * active_cacheline_dec_overlap() returns -1 in that case
    	 */
    	if (active_cacheline_dec_overlap(cln) < 0)
    		radix_tree_delete(&dma_active_cacheline, cln);
    	spin_unlock_irqrestore(&radix_lock, flags);
    }
    
    /**
     * debug_dma_assert_idle() - assert that a page is not undergoing dma
     * @page: page to lookup in the dma_active_cacheline tree
     *
     * Place a call to this routine in cases where the cpu touching the page
     * before the dma completes (page is dma_unmapped) will lead to data
     * corruption.
     */
    void debug_dma_assert_idle(struct page *page)
    {
    	static struct dma_debug_entry *ents[CACHELINES_PER_PAGE];
    	struct dma_debug_entry *entry = NULL;
    	void **results = (void **) &ents;
    	unsigned int nents, i;
    	unsigned long flags;
    	phys_addr_t cln;
    
    	if (dma_debug_disabled())
    		return;
    
    	if (!page)
    		return;
    
    	cln = (phys_addr_t) page_to_pfn(page) << CACHELINE_PER_PAGE_SHIFT;
    	spin_lock_irqsave(&radix_lock, flags);
    	nents = radix_tree_gang_lookup(&dma_active_cacheline, results, cln,
    				       CACHELINES_PER_PAGE);
    	for (i = 0; i < nents; i++) {
    		phys_addr_t ent_cln = to_cacheline_number(ents[i]);
    
    		if (ent_cln == cln) {
    			entry = ents[i];
    			break;
    		} else if (ent_cln >= cln + CACHELINES_PER_PAGE)
    			break;
    	}
    	spin_unlock_irqrestore(&radix_lock, flags);
    
    	if (!entry)
    		return;
    
    	cln = to_cacheline_number(entry);
    	err_printk(entry->dev, entry,
    		   "cpu touching an active dma mapped cacheline [cln=%pa]\n",
    		   &cln);
    }
    
    /*
     * Wrapper function for adding an entry to the hash.
     * This function takes care of locking itself.
     */
    static void add_dma_entry(struct dma_debug_entry *entry)
    {
    	struct hash_bucket *bucket;
    	unsigned long flags;
    	int rc;
    
    	bucket = get_hash_bucket(entry, &flags);
    	hash_bucket_add(bucket, entry);
    	put_hash_bucket(bucket, &flags);
    
    	rc = active_cacheline_insert(entry);
    	if (rc == -ENOMEM) {
    		pr_err("cacheline tracking ENOMEM, dma-debug disabled\n");
    		global_disable = true;
    	}
    
    	/* TODO: report -EEXIST errors here as overlapping mappings are
    	 * not supported by the DMA API
    	 */
    }
    
    static int dma_debug_create_entries(gfp_t gfp)
    {
    	struct dma_debug_entry *entry;
    	int i;
    
    	entry = (void *)get_zeroed_page(gfp);
    	if (!entry)
    		return -ENOMEM;
    
    	for (i = 0; i < DMA_DEBUG_DYNAMIC_ENTRIES; i++)
    		list_add_tail(&entry[i].list, &free_entries);
    
    	num_free_entries += DMA_DEBUG_DYNAMIC_ENTRIES;
    	nr_total_entries += DMA_DEBUG_DYNAMIC_ENTRIES;
    
    	return 0;
    }
    
    static struct dma_debug_entry *__dma_entry_alloc(void)
    {
    	struct dma_debug_entry *entry;
    
    	entry = list_entry(free_entries.next, struct dma_debug_entry, list);
    	list_del(&entry->list);
    	memset(entry, 0, sizeof(*entry));
    
    	num_free_entries -= 1;
    	if (num_free_entries < min_free_entries)
    		min_free_entries = num_free_entries;
    
    	return entry;
    }
    
    void __dma_entry_alloc_check_leak(void)
    {
    	u32 tmp = nr_total_entries % nr_prealloc_entries;
    
    	/* Shout each time we tick over some multiple of the initial pool */
    	if (tmp < DMA_DEBUG_DYNAMIC_ENTRIES) {
    		pr_info("dma_debug_entry pool grown to %u (%u00%%)\n",
    			nr_total_entries,
    			(nr_total_entries / nr_prealloc_entries));
    	}
    }
    
    /* struct dma_entry allocator
     *
     * The next two functions implement the allocator for
     * struct dma_debug_entries.
     */
    static struct dma_debug_entry *dma_entry_alloc(void)
    {
    	struct dma_debug_entry *entry;
    	unsigned long flags;
    
    	spin_lock_irqsave(&free_entries_lock, flags);
    	if (num_free_entries == 0) {
    		if (dma_debug_create_entries(GFP_ATOMIC)) {
    			global_disable = true;
    			spin_unlock_irqrestore(&free_entries_lock, flags);
    			pr_err("debugging out of memory - disabling\n");
    			return NULL;
    		}
    		__dma_entry_alloc_check_leak();
    	}
    
    	entry = __dma_entry_alloc();
    
    	spin_unlock_irqrestore(&free_entries_lock, flags);
    
    #ifdef CONFIG_STACKTRACE
    	entry->stacktrace.max_entries = DMA_DEBUG_STACKTRACE_ENTRIES;
    	entry->stacktrace.entries = entry->st_entries;
    	entry->stacktrace.skip = 2;
    	save_stack_trace(&entry->stacktrace);
    #endif
    
    	return entry;
    }
    
    static void dma_entry_free(struct dma_debug_entry *entry)
    {
    	unsigned long flags;
    
    	active_cacheline_remove(entry);
    
    	/*
    	 * add to beginning of the list - this way the entries are
    	 * more likely cache hot when they are reallocated.
    	 */
    	spin_lock_irqsave(&free_entries_lock, flags);
    	list_add(&entry->list, &free_entries);
    	num_free_entries += 1;
    	spin_unlock_irqrestore(&free_entries_lock, flags);
    }
    
    /*
     * DMA-API debugging init code
     *
     * The init code does two things:
     *   1. Initialize core data structures
     *   2. Preallocate a given number of dma_debug_entry structs
     */
    
    static ssize_t filter_read(struct file *file, char __user *user_buf,
    			   size_t count, loff_t *ppos)
    {
    	char buf[NAME_MAX_LEN + 1];
    	unsigned long flags;
    	int len;
    
    	if (!current_driver_name[0])
    		return 0;
    
    	/*
    	 * We can't copy to userspace directly because current_driver_name can
    	 * only be read under the driver_name_lock with irqs disabled. So
    	 * create a temporary copy first.
    	 */
    	read_lock_irqsave(&driver_name_lock, flags);
    	len = scnprintf(buf, NAME_MAX_LEN + 1, "%s\n", current_driver_name);
    	read_unlock_irqrestore(&driver_name_lock, flags);
    
    	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
    }
    
    static ssize_t filter_write(struct file *file, const char __user *userbuf,
    			    size_t count, loff_t *ppos)
    {
    	char buf[NAME_MAX_LEN];
    	unsigned long flags;
    	size_t len;
    	int i;
    
    	/*
    	 * We can't copy from userspace directly. Access to
    	 * current_driver_name is protected with a write_lock with irqs
    	 * disabled. Since copy_from_user can fault and may sleep we
    	 * need to copy to temporary buffer first
    	 */
    	len = min(count, (size_t)(NAME_MAX_LEN - 1));
    	if (copy_from_user(buf, userbuf, len))
    		return -EFAULT;
    
    	buf[len] = 0;
    
    	write_lock_irqsave(&driver_name_lock, flags);
    
    	/*
    	 * Now handle the string we got from userspace very carefully.
    	 * The rules are:
    	 *         - only use the first token we got
    	 *         - token delimiter is everything looking like a space
    	 *           character (' ', '\n', '\t' ...)
    	 *
    	 */
    	if (!isalnum(buf[0])) {
    		/*
    		 * If the first character userspace gave us is not
    		 * alphanumerical then assume the filter should be
    		 * switched off.
    		 */
    		if (current_driver_name[0])
    			pr_info("switching off dma-debug driver filter\n");
    		current_driver_name[0] = 0;
    		current_driver = NULL;
    		goto out_unlock;
    	}
    
    	/*
    	 * Now parse out the first token and use it as the name for the
    	 * driver to filter for.
    	 */
    	for (i = 0; i < NAME_MAX_LEN - 1; ++i) {
    		current_driver_name[i] = buf[i];
    		if (isspace(buf[i]) || buf[i] == ' ' || buf[i] == 0)
    			break;
    	}
    	current_driver_name[i] = 0;
    	current_driver = NULL;
    
    	pr_info("enable driver filter for driver [%s]\n",
    		current_driver_name);
    
    out_unlock:
    	write_unlock_irqrestore(&driver_name_lock, flags);
    
    	return count;
    }
    
    static const struct file_operations filter_fops = {
    	.read  = filter_read,
    	.write = filter_write,
    	.llseek = default_llseek,
    };
    
    static int dma_debug_fs_init(void)
    {
    	dma_debug_dent = debugfs_create_dir("dma-api", NULL);
    	if (!dma_debug_dent) {
    		pr_err("can not create debugfs directory\n");
    		return -ENOMEM;
    	}
    
    	global_disable_dent = debugfs_create_bool("disabled", 0444,
    			dma_debug_dent,
    			&global_disable);
    	if (!global_disable_dent)
    		goto out_err;
    
    	error_count_dent = debugfs_create_u32("error_count", 0444,
    			dma_debug_dent, &error_count);
    	if (!error_count_dent)
    		goto out_err;
    
    	show_all_errors_dent = debugfs_create_u32("all_errors", 0644,
    			dma_debug_dent,
    			&show_all_errors);
    	if (!show_all_errors_dent)
    		goto out_err;
    
    	show_num_errors_dent = debugfs_create_u32("num_errors", 0644,
    			dma_debug_dent,
    			&show_num_errors);
    	if (!show_num_errors_dent)
    		goto out_err;
    
    	num_free_entries_dent = debugfs_create_u32("num_free_entries", 0444,
    			dma_debug_dent,
    			&num_free_entries);
    	if (!num_free_entries_dent)
    		goto out_err;
    
    	min_free_entries_dent = debugfs_create_u32("min_free_entries", 0444,
    			dma_debug_dent,
    			&min_free_entries);
    	if (!min_free_entries_dent)
    		goto out_err;
    
    	nr_total_entries_dent = debugfs_create_u32("nr_total_entries", 0444,
    			dma_debug_dent,
    			&nr_total_entries);
    	if (!nr_total_entries_dent)
    		goto out_err;
    
    	filter_dent = debugfs_create_file("driver_filter", 0644,
    					  dma_debug_dent, NULL, &filter_fops);
    	if (!filter_dent)
    		goto out_err;
    
    	return 0;
    
    out_err:
    	debugfs_remove_recursive(dma_debug_dent);
    
    	return -ENOMEM;
    }
    
    static int device_dma_allocations(struct device *dev, struct dma_debug_entry **out_entry)
    {
    	struct dma_debug_entry *entry;
    	unsigned long flags;
    	int count = 0, i;
    
    	for (i = 0; i < HASH_SIZE; ++i) {
    		spin_lock_irqsave(&dma_entry_hash[i].lock, flags);
    		list_for_each_entry(entry, &dma_entry_hash[i].list, list) {
    			if (entry->dev == dev) {
    				count += 1;
    				*out_entry = entry;
    			}
    		}
    		spin_unlock_irqrestore(&dma_entry_hash[i].lock, flags);
    	}
    
    	return count;
    }
    
    static int dma_debug_device_change(struct notifier_block *nb, unsigned long action, void *data)
    {
    	struct device *dev = data;
    	struct dma_debug_entry *uninitialized_var(entry);
    	int count;
    
    	if (dma_debug_disabled())
    		return 0;
    
    	switch (action) {
    	case BUS_NOTIFY_UNBOUND_DRIVER:
    		count = device_dma_allocations(dev, &entry);
    		if (count == 0)
    			break;
    		err_printk(dev, entry, "device driver has pending "
    				"DMA allocations while released from device "
    				"[count=%d]\n"
    				"One of leaked entries details: "
    				"[device address=0x%016llx] [size=%llu bytes] "
    				"[mapped with %s] [mapped as %s]\n",
    			count, entry->dev_addr, entry->size,
    			dir2name[entry->direction], type2name[entry->type]);
    		break;
    	default:
    		break;
    	}
    
    	return 0;
    }
    
    void dma_debug_add_bus(struct bus_type *bus)
    {
    	struct notifier_block *nb;
    
    	if (dma_debug_disabled())
    		return;
    
    	nb = kzalloc(sizeof(struct notifier_block), GFP_KERNEL);
    	if (nb == NULL) {
    		pr_err("dma_debug_add_bus: out of memory\n");
    		return;
    	}
    
    	nb->notifier_call = dma_debug_device_change;
    
    	bus_register_notifier(bus, nb);
    }
    
    static int dma_debug_init(void)
    {
    	int i, nr_pages;
    
    	/* Do not use dma_debug_initialized here, since we really want to be
    	 * called to set dma_debug_initialized
    	 */
    	if (global_disable)
    		return 0;
    
    	for (i = 0; i < HASH_SIZE; ++i) {
    		INIT_LIST_HEAD(&dma_entry_hash[i].list);
    		spin_lock_init(&dma_entry_hash[i].lock);
    	}
    
    	if (dma_debug_fs_init() != 0) {
    		pr_err("error creating debugfs entries - disabling\n");
    		global_disable = true;
    
    		return 0;
    	}
    
    	nr_pages = DIV_ROUND_UP(nr_prealloc_entries, DMA_DEBUG_DYNAMIC_ENTRIES);
    	for (i = 0; i < nr_pages; ++i)
    		dma_debug_create_entries(GFP_KERNEL);
    	if (num_free_entries >= nr_prealloc_entries) {
    		pr_info("preallocated %d debug entries\n", nr_total_entries);
    	} else if (num_free_entries > 0) {
    		pr_warn("%d debug entries requested but only %d allocated\n",
    			nr_prealloc_entries, nr_total_entries);
    	} else {
    		pr_err("debugging out of memory error - disabled\n");
    		global_disable = true;
    
    		return 0;
    	}
    	min_free_entries = num_free_entries;
    
    	dma_debug_initialized = true;
    
    	pr_info("debugging enabled by kernel config\n");
    	return 0;
    }
    core_initcall(dma_debug_init);
    
    static __init int dma_debug_cmdline(char *str)
    {
    	if (!str)
    		return -EINVAL;
    
    	if (strncmp(str, "off", 3) == 0) {
    		pr_info("debugging disabled on kernel command line\n");
    		global_disable = true;
    	}
    
    	return 0;
    }
    
    static __init int dma_debug_entries_cmdline(char *str)
    {
    	if (!str)
    		return -EINVAL;
    	if (!get_option(&str, &nr_prealloc_entries))
    		nr_prealloc_entries = PREALLOC_DMA_DEBUG_ENTRIES;
    	return 0;
    }
    
    __setup("dma_debug=", dma_debug_cmdline);
    __setup("dma_debug_entries=", dma_debug_entries_cmdline);
    
    static void check_unmap(struct dma_debug_entry *ref)
    {
    	struct dma_debug_entry *entry;
    	struct hash_bucket *bucket;
    	unsigned long flags;
    
    	bucket = get_hash_bucket(ref, &flags);
    	entry = bucket_find_exact(bucket, ref);
    
    	if (!entry) {
    		/* must drop lock before calling dma_mapping_error */
    		put_hash_bucket(bucket, &flags);
    
    		if (dma_mapping_error(ref->dev, ref->dev_addr)) {
    			err_printk(ref->dev, NULL,
    				   "device driver tries to free an "
    				   "invalid DMA memory address\n");
    		} else {
    			err_printk(ref->dev, NULL,
    				   "device driver tries to free DMA "
    				   "memory it has not allocated [device "
    				   "address=0x%016llx] [size=%llu bytes]\n",
    				   ref->dev_addr, ref->size);
    		}
    		return;
    	}
    
    	if (ref->size != entry->size) {
    		err_printk(ref->dev, entry, "device driver frees "
    			   "DMA memory with different size "
    			   "[device address=0x%016llx] [map size=%llu bytes] "
    			   "[unmap size=%llu bytes]\n",
    			   ref->dev_addr, entry->size, ref->size);
    	}
    
    	if (ref->type != entry->type) {
    		err_printk(ref->dev, entry, "device driver frees "
    			   "DMA memory with wrong function "
    			   "[device address=0x%016llx] [size=%llu bytes] "
    			   "[mapped as %s] [unmapped as %s]\n",
    			   ref->dev_addr, ref->size,
    			   type2name[entry->type], type2name[ref->type]);
    	} else if ((entry->type == dma_debug_coherent) &&
    		   (phys_addr(ref) != phys_addr(entry))) {
    		err_printk(ref->dev, entry, "device driver frees "
    			   "DMA memory with different CPU address "
    			   "[device address=0x%016llx] [size=%llu bytes] "
    			   "[cpu alloc address=0x%016llx] "
    			   "[cpu free address=0x%016llx]",
    			   ref->dev_addr, ref->size,
    			   phys_addr(entry),
    			   phys_addr(ref));
    	}
    
    	if (ref->sg_call_ents && ref->type == dma_debug_sg &&
    	    ref->sg_call_ents != entry->sg_call_ents) {
    		err_printk(ref->dev, entry, "device driver frees "
    			   "DMA sg list with different entry count "
    			   "[map count=%d] [unmap count=%d]\n",
    			   entry->sg_call_ents, ref->sg_call_ents);
    	}
    
    	/*
    	 * This may be no bug in reality - but most implementations of the
    	 * DMA API don't handle this properly, so check for it here
    	 */
    	if (ref->direction != entry->direction) {
    		err_printk(ref->dev, entry, "device driver frees "
    			   "DMA memory with different direction "
    			   "[device address=0x%016llx] [size=%llu bytes] "
    			   "[mapped with %s] [unmapped with %s]\n",
    			   ref->dev_addr, ref->size,
    			   dir2name[entry->direction],
    			   dir2name[ref->direction]);
    	}
    
    	/*
    	 * Drivers should use dma_mapping_error() to check the returned
    	 * addresses of dma_map_single() and dma_map_page().
    	 * If not, print this warning message. See Documentation/DMA-API.txt.
    	 */
    	if (entry->map_err_type == MAP_ERR_NOT_CHECKED) {
    		err_printk(ref->dev, entry,
    			   "device driver failed to check map error"
    			   "[device address=0x%016llx] [size=%llu bytes] "
    			   "[mapped as %s]",
    			   ref->dev_addr, ref->size,
    			   type2name[entry->type]);
    	}
    
    	hash_bucket_del(entry);
    	dma_entry_free(entry);
    
    	put_hash_bucket(bucket, &flags);
    }
    
    static void check_for_stack(struct device *dev,
    			    struct page *page, size_t offset)
    {
    	void *addr;
    	struct vm_struct *stack_vm_area = task_stack_vm_area(current);
    
    	if (!stack_vm_area) {
    		/* Stack is direct-mapped. */
    		if (PageHighMem(page))
    			return;
    		addr = page_address(page) + offset;
    		if (object_is_on_stack(addr))
    			err_printk(dev, NULL, "device driver maps memory from stack [addr=%p]\n", addr);
    	} else {
    		/* Stack is vmalloced. */
    		int i;
    
    		for (i = 0; i < stack_vm_area->nr_pages; i++) {
    			if (page != stack_vm_area->pages[i])
    				continue;
    
    			addr = (u8 *)current->stack + i * PAGE_SIZE + offset;
    			err_printk(dev, NULL, "device driver maps memory from stack [probable addr=%p]\n", addr);
    			break;
    		}
    	}
    }
    
    static inline bool overlap(void *addr, unsigned long len, void *start, void *end)
    {
    	unsigned long a1 = (unsigned long)addr;
    	unsigned long b1 = a1 + len;
    	unsigned long a2 = (unsigned long)start;
    	unsigned long b2 = (unsigned long)end;
    
    	return !(b1 <= a2 || a1 >= b2);
    }
    
    static void check_for_illegal_area(struct device *dev, void *addr, unsigned long len)
    {
    	if (overlap(addr, len, _stext, _etext) ||
    	    overlap(addr, len, __start_rodata, __end_rodata))
    		err_printk(dev, NULL, "device driver maps memory from kernel text or rodata [addr=%p] [len=%lu]\n", addr, len);
    }
    
    static void check_sync(struct device *dev,
    		       struct dma_debug_entry *ref,
    		       bool to_cpu)
    {
    	struct dma_debug_entry *entry;
    	struct hash_bucket *bucket;
    	unsigned long flags;
    
    	bucket = get_hash_bucket(ref, &flags);
    
    	entry = bucket_find_contain(&bucket, ref, &flags);
    
    	if (!entry) {
    		err_printk(dev, NULL, "device driver tries "
    				"to sync DMA memory it has not allocated "
    				"[device address=0x%016llx] [size=%llu bytes]\n",
    				(unsigned long long)ref->dev_addr, ref->size);
    		goto out;
    	}
    
    	if (ref->size > entry->size) {
    		err_printk(dev, entry, "device driver syncs"
    				" DMA memory outside allocated range "
    				"[device address=0x%016llx] "
    				"[allocation size=%llu bytes] "
    				"[sync offset+size=%llu]\n",
    				entry->dev_addr, entry->size,
    				ref->size);
    	}
    
    	if (entry->direction == DMA_BIDIRECTIONAL)
    		goto out;
    
    	if (ref->direction != entry->direction) {
    		err_printk(dev, entry, "device driver syncs "
    				"DMA memory with different direction "
    				"[device address=0x%016llx] [size=%llu bytes] "
    				"[mapped with %s] [synced with %s]\n",
    				(unsigned long long)ref->dev_addr, entry->size,
    				dir2name[entry->direction],
    				dir2name[ref->direction]);
    	}
    
    	if (to_cpu && !(entry->direction == DMA_FROM_DEVICE) &&
    		      !(ref->direction == DMA_TO_DEVICE))
    		err_printk(dev, entry, "device driver syncs "
    				"device read-only DMA memory for cpu "
    				"[device address=0x%016llx] [size=%llu bytes] "
    				"[mapped with %s] [synced with %s]\n",
    				(unsigned long long)ref->dev_addr, entry->size,
    				dir2name[entry->direction],
    				dir2name[ref->direction]);
    
    	if (!to_cpu && !(entry->direction == DMA_TO_DEVICE) &&
    		       !(ref->direction == DMA_FROM_DEVICE))
    		err_printk(dev, entry, "device driver syncs "
    				"device write-only DMA memory to device "
    				"[device address=0x%016llx] [size=%llu bytes] "
    				"[mapped with %s] [synced with %s]\n",
    				(unsigned long long)ref->dev_addr, entry->size,
    				dir2name[entry->direction],
    				dir2name[ref->direction]);
    
    	if (ref->sg_call_ents && ref->type == dma_debug_sg &&
    	    ref->sg_call_ents != entry->sg_call_ents) {
    		err_printk(ref->dev, entry, "device driver syncs "
    			   "DMA sg list with different entry count "
    			   "[map count=%d] [sync count=%d]\n",
    			   entry->sg_call_ents, ref->sg_call_ents);
    	}
    
    out:
    	put_hash_bucket(bucket, &flags);
    }
    
    static void check_sg_segment(struct device *dev, struct scatterlist *sg)
    {
    #ifdef CONFIG_DMA_API_DEBUG_SG
    	unsigned int max_seg = dma_get_max_seg_size(dev);
    	u64 start, end, boundary = dma_get_seg_boundary(dev);
    
    	/*
    	 * Either the driver forgot to set dma_parms appropriately, or
    	 * whoever generated the list forgot to check them.
    	 */
    	if (sg->length > max_seg)
    		err_printk(dev, NULL, "mapping sg segment longer than device claims to support [len=%u] [max=%u]\n",
    			   sg->length, max_seg);
    	/*
    	 * In some cases this could potentially be the DMA API
    	 * implementation's fault, but it would usually imply that
    	 * the scatterlist was built inappropriately to begin with.
    	 */
    	start = sg_dma_address(sg);
    	end = start + sg_dma_len(sg) - 1;
    	if ((start ^ end) & ~boundary)
    		err_printk(dev, NULL, "mapping sg segment across boundary [start=0x%016llx] [end=0x%016llx] [boundary=0x%016llx]\n",
    			   start, end, boundary);
    #endif
    }
    
    void debug_dma_map_single(struct device *dev, const void *addr,
    			    unsigned long len)
    {
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	if (!virt_addr_valid(addr))
    		err_printk(dev, NULL, "device driver maps memory from invalid area [addr=%p] [len=%lu]\n",
    			   addr, len);
    
    	if (is_vmalloc_addr(addr))
    		err_printk(dev, NULL, "device driver maps memory from vmalloc area [addr=%p] [len=%lu]\n",
    			   addr, len);
    }
    EXPORT_SYMBOL(debug_dma_map_single);
    
    void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
    			size_t size, int direction, dma_addr_t dma_addr)
    {
    	struct dma_debug_entry *entry;
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	if (dma_mapping_error(dev, dma_addr))
    		return;
    
    	entry = dma_entry_alloc();
    	if (!entry)
    		return;
    
    	entry->dev       = dev;
    	entry->type      = dma_debug_single;
    	entry->pfn	 = page_to_pfn(page);
    	entry->offset	 = offset,
    	entry->dev_addr  = dma_addr;
    	entry->size      = size;
    	entry->direction = direction;
    	entry->map_err_type = MAP_ERR_NOT_CHECKED;
    
    	check_for_stack(dev, page, offset);
    
    	if (!PageHighMem(page)) {
    		void *addr = page_address(page) + offset;
    
    		check_for_illegal_area(dev, addr, size);
    	}
    
    	add_dma_entry(entry);
    }
    EXPORT_SYMBOL(debug_dma_map_page);
    
    void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
    {
    	struct dma_debug_entry ref;
    	struct dma_debug_entry *entry;
    	struct hash_bucket *bucket;
    	unsigned long flags;
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	ref.dev = dev;
    	ref.dev_addr = dma_addr;
    	bucket = get_hash_bucket(&ref, &flags);
    
    	list_for_each_entry(entry, &bucket->list, list) {
    		if (!exact_match(&ref, entry))
    			continue;
    
    		/*
    		 * The same physical address can be mapped multiple
    		 * times. Without a hardware IOMMU this results in the
    		 * same device addresses being put into the dma-debug
    		 * hash multiple times too. This can result in false
    		 * positives being reported. Therefore we implement a
    		 * best-fit algorithm here which updates the first entry
    		 * from the hash which fits the reference value and is
    		 * not currently listed as being checked.
    		 */
    		if (entry->map_err_type == MAP_ERR_NOT_CHECKED) {
    			entry->map_err_type = MAP_ERR_CHECKED;
    			break;
    		}
    	}
    
    	put_hash_bucket(bucket, &flags);
    }
    EXPORT_SYMBOL(debug_dma_mapping_error);
    
    void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
    			  size_t size, int direction)
    {
    	struct dma_debug_entry ref = {
    		.type           = dma_debug_single,
    		.dev            = dev,
    		.dev_addr       = addr,
    		.size           = size,
    		.direction      = direction,
    	};
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    	check_unmap(&ref);
    }
    EXPORT_SYMBOL(debug_dma_unmap_page);
    
    void debug_dma_map_sg(struct device *dev, struct scatterlist *sg,
    		      int nents, int mapped_ents, int direction)
    {
    	struct dma_debug_entry *entry;
    	struct scatterlist *s;
    	int i;
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	for_each_sg(sg, s, mapped_ents, i) {
    		entry = dma_entry_alloc();
    		if (!entry)
    			return;
    
    		entry->type           = dma_debug_sg;
    		entry->dev            = dev;
    		entry->pfn	      = page_to_pfn(sg_page(s));
    		entry->offset	      = s->offset,
    		entry->size           = sg_dma_len(s);
    		entry->dev_addr       = sg_dma_address(s);
    		entry->direction      = direction;
    		entry->sg_call_ents   = nents;
    		entry->sg_mapped_ents = mapped_ents;
    
    		check_for_stack(dev, sg_page(s), s->offset);
    
    		if (!PageHighMem(sg_page(s))) {
    			check_for_illegal_area(dev, sg_virt(s), sg_dma_len(s));
    		}
    
    		check_sg_segment(dev, s);
    
    		add_dma_entry(entry);
    	}
    }
    EXPORT_SYMBOL(debug_dma_map_sg);
    
    static int get_nr_mapped_entries(struct device *dev,
    				 struct dma_debug_entry *ref)
    {
    	struct dma_debug_entry *entry;
    	struct hash_bucket *bucket;
    	unsigned long flags;
    	int mapped_ents;
    
    	bucket       = get_hash_bucket(ref, &flags);
    	entry        = bucket_find_exact(bucket, ref);
    	mapped_ents  = 0;
    
    	if (entry)
    		mapped_ents = entry->sg_mapped_ents;
    	put_hash_bucket(bucket, &flags);
    
    	return mapped_ents;
    }
    
    void debug_dma_unmap_sg(struct device *dev, struct scatterlist *sglist,
    			int nelems, int dir)
    {
    	struct scatterlist *s;
    	int mapped_ents = 0, i;
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	for_each_sg(sglist, s, nelems, i) {
    
    		struct dma_debug_entry ref = {
    			.type           = dma_debug_sg,
    			.dev            = dev,
    			.pfn		= page_to_pfn(sg_page(s)),
    			.offset		= s->offset,
    			.dev_addr       = sg_dma_address(s),
    			.size           = sg_dma_len(s),
    			.direction      = dir,
    			.sg_call_ents   = nelems,
    		};
    
    		if (mapped_ents && i >= mapped_ents)
    			break;
    
    		if (!i)
    			mapped_ents = get_nr_mapped_entries(dev, &ref);
    
    		check_unmap(&ref);
    	}
    }
    EXPORT_SYMBOL(debug_dma_unmap_sg);
    
    void debug_dma_alloc_coherent(struct device *dev, size_t size,
    			      dma_addr_t dma_addr, void *virt)
    {
    	struct dma_debug_entry *entry;
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	if (unlikely(virt == NULL))
    		return;
    
    	/* handle vmalloc and linear addresses */
    	if (!is_vmalloc_addr(virt) && !virt_addr_valid(virt))
    		return;
    
    	entry = dma_entry_alloc();
    	if (!entry)
    		return;
    
    	entry->type      = dma_debug_coherent;
    	entry->dev       = dev;
    	entry->offset	 = offset_in_page(virt);
    	entry->size      = size;
    	entry->dev_addr  = dma_addr;
    	entry->direction = DMA_BIDIRECTIONAL;
    
    	if (is_vmalloc_addr(virt))
    		entry->pfn = vmalloc_to_pfn(virt);
    	else
    		entry->pfn = page_to_pfn(virt_to_page(virt));
    
    	add_dma_entry(entry);
    }
    EXPORT_SYMBOL(debug_dma_alloc_coherent);
    
    void debug_dma_free_coherent(struct device *dev, size_t size,
    			 void *virt, dma_addr_t addr)
    {
    	struct dma_debug_entry ref = {
    		.type           = dma_debug_coherent,
    		.dev            = dev,
    		.offset		= offset_in_page(virt),
    		.dev_addr       = addr,
    		.size           = size,
    		.direction      = DMA_BIDIRECTIONAL,
    	};
    
    	/* handle vmalloc and linear addresses */
    	if (!is_vmalloc_addr(virt) && !virt_addr_valid(virt))
    		return;
    
    	if (is_vmalloc_addr(virt))
    		ref.pfn = vmalloc_to_pfn(virt);
    	else
    		ref.pfn = page_to_pfn(virt_to_page(virt));
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	check_unmap(&ref);
    }
    EXPORT_SYMBOL(debug_dma_free_coherent);
    
    void debug_dma_map_resource(struct device *dev, phys_addr_t addr, size_t size,
    			    int direction, dma_addr_t dma_addr)
    {
    	struct dma_debug_entry *entry;
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	entry = dma_entry_alloc();
    	if (!entry)
    		return;
    
    	entry->type		= dma_debug_resource;
    	entry->dev		= dev;
    	entry->pfn		= PHYS_PFN(addr);
    	entry->offset		= offset_in_page(addr);
    	entry->size		= size;
    	entry->dev_addr		= dma_addr;
    	entry->direction	= direction;
    	entry->map_err_type	= MAP_ERR_NOT_CHECKED;
    
    	add_dma_entry(entry);
    }
    EXPORT_SYMBOL(debug_dma_map_resource);
    
    void debug_dma_unmap_resource(struct device *dev, dma_addr_t dma_addr,
    			      size_t size, int direction)
    {
    	struct dma_debug_entry ref = {
    		.type           = dma_debug_resource,
    		.dev            = dev,
    		.dev_addr       = dma_addr,
    		.size           = size,
    		.direction      = direction,
    	};
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	check_unmap(&ref);
    }
    EXPORT_SYMBOL(debug_dma_unmap_resource);
    
    void debug_dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle,
    				   size_t size, int direction)
    {
    	struct dma_debug_entry ref;
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	ref.type         = dma_debug_single;
    	ref.dev          = dev;
    	ref.dev_addr     = dma_handle;
    	ref.size         = size;
    	ref.direction    = direction;
    	ref.sg_call_ents = 0;
    
    	check_sync(dev, &ref, true);
    }
    EXPORT_SYMBOL(debug_dma_sync_single_for_cpu);
    
    void debug_dma_sync_single_for_device(struct device *dev,
    				      dma_addr_t dma_handle, size_t size,
    				      int direction)
    {
    	struct dma_debug_entry ref;
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	ref.type         = dma_debug_single;
    	ref.dev          = dev;
    	ref.dev_addr     = dma_handle;
    	ref.size         = size;
    	ref.direction    = direction;
    	ref.sg_call_ents = 0;
    
    	check_sync(dev, &ref, false);
    }
    EXPORT_SYMBOL(debug_dma_sync_single_for_device);
    
    void debug_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
    			       int nelems, int direction)
    {
    	struct scatterlist *s;
    	int mapped_ents = 0, i;
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	for_each_sg(sg, s, nelems, i) {
    
    		struct dma_debug_entry ref = {
    			.type           = dma_debug_sg,
    			.dev            = dev,
    			.pfn		= page_to_pfn(sg_page(s)),
    			.offset		= s->offset,
    			.dev_addr       = sg_dma_address(s),
    			.size           = sg_dma_len(s),
    			.direction      = direction,
    			.sg_call_ents   = nelems,
    		};
    
    		if (!i)
    			mapped_ents = get_nr_mapped_entries(dev, &ref);
    
    		if (i >= mapped_ents)
    			break;
    
    		check_sync(dev, &ref, true);
    	}
    }
    EXPORT_SYMBOL(debug_dma_sync_sg_for_cpu);
    
    void debug_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
    				  int nelems, int direction)
    {
    	struct scatterlist *s;
    	int mapped_ents = 0, i;
    
    	if (unlikely(dma_debug_disabled()))
    		return;
    
    	for_each_sg(sg, s, nelems, i) {
    
    		struct dma_debug_entry ref = {
    			.type           = dma_debug_sg,
    			.dev            = dev,
    			.pfn		= page_to_pfn(sg_page(s)),
    			.offset		= s->offset,
    			.dev_addr       = sg_dma_address(s),
    			.size           = sg_dma_len(s),
    			.direction      = direction,
    			.sg_call_ents   = nelems,
    		};
    		if (!i)
    			mapped_ents = get_nr_mapped_entries(dev, &ref);
    
    		if (i >= mapped_ents)
    			break;
    
    		check_sync(dev, &ref, false);
    	}
    }
    EXPORT_SYMBOL(debug_dma_sync_sg_for_device);
    
    static int __init dma_debug_driver_setup(char *str)
    {
    	int i;
    
    	for (i = 0; i < NAME_MAX_LEN - 1; ++i, ++str) {
    		current_driver_name[i] = *str;
    		if (*str == 0)
    			break;
    	}
    
    	if (current_driver_name[0])
    		pr_info("enable driver filter for driver [%s]\n",
    			current_driver_name);
    
    
    	return 1;
    }
    __setup("dma_debug_driver=", dma_debug_driver_setup);