// SPDX-License-Identifier: GPL-2.0-only

  /*
   * Copyright (C) 2008 Advanced Micro Devices, Inc.
   *
   * Author: Joerg Roedel <joerg.roedel@amd.com>

   */

  #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

  	unsigned int	stack_len;
  	unsigned long	stack_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;

  /* 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:
  ");

  		stack_trace_print(entry->stack_entries, entry->stack_len, 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
  ",

  					 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);

  		cond_resched();

  	}
  }

  
  /*

   * 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
  "),

  		  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]
  ",

  		   &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
  ");

  		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%%)
  ",
  			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
  ");
  			return NULL;
  		}

  		__dma_entry_alloc_check_leak();

  	}

  	entry = __dma_entry_alloc();

  	spin_unlock_irqrestore(&free_entries_lock, flags);

  #ifdef CONFIG_STACKTRACE

  	entry->stack_len = stack_trace_save(entry->stack_entries,
  					    ARRAY_SIZE(entry->stack_entries),
  					    1);

  #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
  ", 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 (' ', '
  ', '\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
  ");

  		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]
  ",

  		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 dump_show(struct seq_file *seq, void *v)
  {
  	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) {
  			seq_printf(seq,
  				   "%s %s %s idx %d P=%llx N=%lx D=%llx L=%llx %s %s
  ",
  				   dev_name(entry->dev),
  				   dev_driver_string(entry->dev),
  				   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);
  	}
  	return 0;
  }
  DEFINE_SHOW_ATTRIBUTE(dump);

  static void dma_debug_fs_init(void)

  {

  	struct dentry *dentry = debugfs_create_dir("dma-api", NULL);

  	debugfs_create_bool("disabled", 0444, dentry, &global_disable);
  	debugfs_create_u32("error_count", 0444, dentry, &error_count);
  	debugfs_create_u32("all_errors", 0644, dentry, &show_all_errors);
  	debugfs_create_u32("num_errors", 0644, dentry, &show_num_errors);
  	debugfs_create_u32("num_free_entries", 0444, dentry, &num_free_entries);
  	debugfs_create_u32("min_free_entries", 0444, dentry, &min_free_entries);
  	debugfs_create_u32("nr_total_entries", 0444, dentry, &nr_total_entries);
  	debugfs_create_file("driver_filter", 0644, dentry, NULL, &filter_fops);

  	debugfs_create_file("dump", 0444, dentry, NULL, &dump_fops);

  }

  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]
  "
  				"One of leaked entries details: "
  				"[device address=0x%016llx] [size=%llu bytes] "
  				"[mapped with %s] [mapped as %s]
  ",
  			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
  ");

  		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);

  	}

  	dma_debug_fs_init();

  	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
  ", nr_total_entries);
  	} else if (num_free_entries > 0) {
  		pr_warn("%d debug entries requested but only %d allocated
  ",
  			nr_prealloc_entries, nr_total_entries);
  	} else {

  		pr_err("debugging out of memory error - disabled
  ");

  		global_disable = true;

  		return 0;

  	}

  	min_free_entries = num_free_entries;

  	dma_debug_initialized = true;

  	pr_info("debugging enabled by kernel config
  ");

  	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
  ");

  		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
  ");
  		} else {
  			err_printk(ref->dev, NULL,

  				   "device driver tries to free DMA "

  				   "memory it has not allocated [device "
  				   "address=0x%016llx] [size=%llu bytes]
  ",
  				   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]
  ",
  			   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]
  ",
  			   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]
  ",
  			   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]
  ",
  			   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]
  ", 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]
  ", 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]
  ", 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]
  ",

  				(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]
  ",
  				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]
  ",

  				(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]
  ",

  				(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]
  ",

  				(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]
  ",
  			   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]
  ",

  			   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]
  ",

  			   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]
  ",

  			   addr, len);
  
  	if (is_vmalloc_addr(addr))

  		err_printk(dev, NULL, "device driver maps memory from vmalloc area [addr=%p] [len=%lu]
  ",

  			   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);
  }

  
  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);
  }

  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]
  ",

  			current_driver_name);

  
  
  	return 1;
  }
  __setup("dma_debug_driver=", dma_debug_driver_setup);