/*
   * 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
   */

  #include <linux/scatterlist.h>

  #include <linux/dma-mapping.h>

  #include <linux/stacktrace.h>

  #include <linux/dma-debug.h>

  #include <linux/spinlock.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)

  enum {
  	dma_debug_single,
  	dma_debug_page,
  	dma_debug_sg,
  	dma_debug_coherent,
  };

  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 {
  	struct list_head list;
  	struct device    *dev;
  	int              type;
  	phys_addr_t      paddr;
  	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 u32 global_disable __read_mostly;

  /* 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 req_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 *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[4] = { "single", "page",
  				    "scather-gather", "coherent" };
  
  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:
  ");

  		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, "%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)
  {
  	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)
  {
  	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, &index, 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);
  }
  
  /*

   * 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 D=%Lx L=%Lx %s %s
  ",

  					 type2name[entry->type], idx,
  					 (unsigned long long)entry->paddr,
  					 entry->dev_addr, entry->size,

  					 dir2name[entry->direction],
  					 maperr2str[entry->map_err_type]);

  			}
  		}
  
  		spin_unlock_irqrestore(&bucket->lock, flags);
  	}
  }
  EXPORT_SYMBOL(debug_dma_dump_mappings);
  
  /*

   * 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;
  
  	bucket = get_hash_bucket(entry, &flags);
  	hash_bucket_add(bucket, entry);
  	put_hash_bucket(bucket, &flags);
  }

  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;
  }

  /* 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 (list_empty(&free_entries)) {

  		pr_err("DMA-API: debugging out of memory - disabling
  ");

  		global_disable = true;

  		spin_unlock_irqrestore(&free_entries_lock, flags);
  		return NULL;

  	}

  	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;
  
  	/*
  	 * 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);
  }

  int dma_debug_resize_entries(u32 num_entries)
  {
  	int i, delta, ret = 0;
  	unsigned long flags;
  	struct dma_debug_entry *entry;
  	LIST_HEAD(tmp);
  
  	spin_lock_irqsave(&free_entries_lock, flags);
  
  	if (nr_total_entries < num_entries) {
  		delta = num_entries - nr_total_entries;
  
  		spin_unlock_irqrestore(&free_entries_lock, flags);
  
  		for (i = 0; i < delta; i++) {
  			entry = kzalloc(sizeof(*entry), GFP_KERNEL);
  			if (!entry)
  				break;
  
  			list_add_tail(&entry->list, &tmp);
  		}
  
  		spin_lock_irqsave(&free_entries_lock, flags);
  
  		list_splice(&tmp, &free_entries);
  		nr_total_entries += i;
  		num_free_entries += i;
  	} else {
  		delta = nr_total_entries - num_entries;
  
  		for (i = 0; i < delta && !list_empty(&free_entries); i++) {
  			entry = __dma_entry_alloc();
  			kfree(entry);
  		}
  
  		nr_total_entries -= i;
  	}
  
  	if (nr_total_entries != num_entries)
  		ret = 1;
  
  	spin_unlock_irqrestore(&free_entries_lock, flags);
  
  	return ret;
  }
  EXPORT_SYMBOL(dma_debug_resize_entries);

  /*
   * 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 int prealloc_memory(u32 num_entries)
  {
  	struct dma_debug_entry *entry, *next_entry;
  	int i;
  
  	for (i = 0; i < num_entries; ++i) {
  		entry = kzalloc(sizeof(*entry), GFP_KERNEL);
  		if (!entry)
  			goto out_err;
  
  		list_add_tail(&entry->list, &free_entries);
  	}
  
  	num_free_entries = num_entries;
  	min_free_entries = num_entries;

  	pr_info("DMA-API: preallocated %d debug entries
  ", num_entries);

  
  	return 0;
  
  out_err:
  
  	list_for_each_entry_safe(entry, next_entry, &free_entries, list) {
  		list_del(&entry->list);
  		kfree(entry);
  	}
  
  	return -ENOMEM;
  }

  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("DMA-API: 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("DMA-API: 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 dma_debug_fs_init(void)
  {
  	dma_debug_dent = debugfs_create_dir("dma-api", NULL);
  	if (!dma_debug_dent) {

  		pr_err("DMA-API: can not create debugfs directory
  ");

  		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;

  	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;

  	local_irq_save(flags);

  	for (i = 0; i < HASH_SIZE; ++i) {

  		spin_lock(&dma_entry_hash[i].lock);

  		list_for_each_entry(entry, &dma_entry_hash[i].list, list) {

  			if (entry->dev == dev) {

  				count += 1;

  				*out_entry = entry;
  			}

  		}

  		spin_unlock(&dma_entry_hash[i].lock);

  	}

  	local_irq_restore(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 (global_disable)

  		return 0;

  
  	switch (action) {
  	case BUS_NOTIFY_UNBOUND_DRIVER:

  		count = device_dma_allocations(dev, &entry);

  		if (count == 0)
  			break;

  		err_printk(dev, entry, "DMA-API: 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 (global_disable)
  		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);

  }

  /*
   * Let the architectures decide how many entries should be preallocated.
   */
  void dma_debug_init(u32 num_entries)
  {
  	int i;
  
  	if (global_disable)
  		return;
  
  	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("DMA-API: error creating debugfs entries - disabling
  ");

  		global_disable = true;
  
  		return;
  	}

  	if (req_entries)
  		num_entries = req_entries;

  	if (prealloc_memory(num_entries) != 0) {

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

  		global_disable = true;
  
  		return;
  	}

  	nr_total_entries = num_free_entries;

  	pr_info("DMA-API: debugging enabled by kernel config
  ");

  }

  static __init int dma_debug_cmdline(char *str)
  {
  	if (!str)
  		return -EINVAL;
  
  	if (strncmp(str, "off", 3) == 0) {

  		pr_info("DMA-API: debugging disabled on kernel command line
  ");

  		global_disable = true;
  	}
  
  	return 0;
  }
  
  static __init int dma_debug_entries_cmdline(char *str)
  {
  	int res;
  
  	if (!str)
  		return -EINVAL;
  
  	res = get_option(&str, &req_entries);
  
  	if (!res)
  		req_entries = 0;
  
  	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,

  				   "DMA-API: device driver tries to free an "
  				   "invalid DMA memory address
  ");
  		} else {
  			err_printk(ref->dev, NULL,
  				   "DMA-API: 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, "DMA-API: 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, "DMA-API: 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) &&
  		   (ref->paddr != entry->paddr)) {

  		err_printk(ref->dev, entry, "DMA-API: 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,

  			   (unsigned long long)entry->paddr,
  			   (unsigned long long)ref->paddr);

  	}
  
  	if (ref->sg_call_ents && ref->type == dma_debug_sg &&
  	    ref->sg_call_ents != entry->sg_call_ents) {

  		err_printk(ref->dev, entry, "DMA-API: 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, "DMA-API: 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]);
  	}

  	if (entry->map_err_type == MAP_ERR_NOT_CHECKED) {
  		err_printk(ref->dev, entry,
  			   "DMA-API: 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, void *addr)
  {
  	if (object_is_on_stack(addr))

  		err_printk(dev, NULL, "DMA-API: device driver maps memory from"
  				"stack [addr=%p]
  ", addr);

  }

  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, _text, _etext) ||
  	    overlap(addr, len, __start_rodata, __end_rodata))
  		err_printk(dev, NULL, "DMA-API: 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, "DMA-API: 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, "DMA-API: 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, "DMA-API: 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, "DMA-API: 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, "DMA-API: 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]);

  
  out:
  	put_hash_bucket(bucket, &flags);

  }

  void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
  			size_t size, int direction, dma_addr_t dma_addr,
  			bool map_single)
  {
  	struct dma_debug_entry *entry;
  
  	if (unlikely(global_disable))
  		return;

  	if (dma_mapping_error(dev, dma_addr))

  		return;
  
  	entry = dma_entry_alloc();
  	if (!entry)
  		return;
  
  	entry->dev       = dev;
  	entry->type      = dma_debug_page;
  	entry->paddr     = page_to_phys(page) + offset;
  	entry->dev_addr  = dma_addr;
  	entry->size      = size;
  	entry->direction = direction;

  	entry->map_err_type = MAP_ERR_NOT_CHECKED;

  	if (map_single)

  		entry->type = dma_debug_single;

  
  	if (!PageHighMem(page)) {

  		void *addr = page_address(page) + offset;

  		check_for_stack(dev, addr);
  		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(global_disable))
  		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, bool map_single)
  {
  	struct dma_debug_entry ref = {
  		.type           = dma_debug_page,
  		.dev            = dev,
  		.dev_addr       = addr,
  		.size           = size,
  		.direction      = direction,
  	};
  
  	if (unlikely(global_disable))
  		return;
  
  	if (map_single)
  		ref.type = dma_debug_single;
  
  	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(global_disable))
  		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->paddr          = sg_phys(s);

  		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;

  		if (!PageHighMem(sg_page(s))) {
  			check_for_stack(dev, sg_virt(s));

  			check_for_illegal_area(dev, sg_virt(s), sg_dma_len(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(global_disable))
  		return;
  
  	for_each_sg(sglist, s, nelems, i) {
  
  		struct dma_debug_entry ref = {
  			.type           = dma_debug_sg,
  			.dev            = dev,
  			.paddr          = sg_phys(s),

  			.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(global_disable))
  		return;
  
  	if (unlikely(virt == NULL))
  		return;
  
  	entry = dma_entry_alloc();
  	if (!entry)
  		return;
  
  	entry->type      = dma_debug_coherent;
  	entry->dev       = dev;
  	entry->paddr     = virt_to_phys(virt);
  	entry->size      = size;
  	entry->dev_addr  = dma_addr;
  	entry->direction = DMA_BIDIRECTIONAL;
  
  	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,
  		.paddr          = virt_to_phys(virt),
  		.dev_addr       = addr,
  		.size           = size,
  		.direction      = DMA_BIDIRECTIONAL,
  	};
  
  	if (unlikely(global_disable))
  		return;
  
  	check_unmap(&ref);
  }
  EXPORT_SYMBOL(debug_dma_free_coherent);

  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(global_disable))
  		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(global_disable))
  		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_single_range_for_cpu(struct device *dev,
  					 dma_addr_t dma_handle,
  					 unsigned long offset, size_t size,
  					 int direction)
  {

  	struct dma_debug_entry ref;

  	if (unlikely(global_disable))
  		return;

  	ref.type         = dma_debug_single;
  	ref.dev          = dev;
  	ref.dev_addr     = dma_handle;
  	ref.size         = offset + size;
  	ref.direction    = direction;
  	ref.sg_call_ents = 0;
  
  	check_sync(dev, &ref, true);

  }
  EXPORT_SYMBOL(debug_dma_sync_single_range_for_cpu);
  
  void debug_dma_sync_single_range_for_device(struct device *dev,
  					    dma_addr_t dma_handle,
  					    unsigned long offset,
  					    size_t size, int direction)
  {

  	struct dma_debug_entry ref;

  	if (unlikely(global_disable))
  		return;

  	ref.type         = dma_debug_single;
  	ref.dev          = dev;
  	ref.dev_addr     = dma_handle;
  	ref.size         = offset + size;
  	ref.direction    = direction;
  	ref.sg_call_ents = 0;
  
  	check_sync(dev, &ref, false);

  }
  EXPORT_SYMBOL(debug_dma_sync_single_range_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(global_disable))
  		return;
  
  	for_each_sg(sg, s, nelems, i) {

  
  		struct dma_debug_entry ref = {
  			.type           = dma_debug_sg,
  			.dev            = dev,
  			.paddr          = sg_phys(s),
  			.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(global_disable))
  		return;
  
  	for_each_sg(sg, s, nelems, i) {

  
  		struct dma_debug_entry ref = {
  			.type           = dma_debug_sg,
  			.dev            = dev,
  			.paddr          = sg_phys(s),
  			.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("DMA-API: enable driver filter for driver [%s]
  ",
  			current_driver_name);

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