text: /*
   * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License as published by the Free
   * Software Foundation; either version 2 of the License, or (at your option)
   * any later version.
   *
   * 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.
   *
   * The full GNU General Public License is included in this distribution in the
   * file called COPYING.
   */
  
  /*
   * This code implements the DMA subsystem. It provides a HW-neutral interface
   * for other kernel code to use asynchronous memory copy capabilities,
   * if present, and allows different HW DMA drivers to register as providing
   * this capability.
   *
   * Due to the fact we are accelerating what is already a relatively fast
   * operation, the code goes to great lengths to avoid additional overhead,
   * such as locking.
   *
   * LOCKING:
   *
   * The subsystem keeps a global list of dma_device structs it is protected by a
   * mutex, dma_list_mutex.
   *
   * A subsystem can get access to a channel by calling dmaengine_get() followed
   * by dma_find_channel(), or if it has need for an exclusive channel it can call
   * dma_request_channel().  Once a channel is allocated a reference is taken
   * against its corresponding driver to disable removal.
   *
   * Each device has a channels list, which runs unlocked but is never modified
   * once the device is registered, it's just setup by the driver.
   *
   * See Documentation/dmaengine.txt for more details
   */
  
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/mm.h>
  #include <linux/device.h>
  #include <linux/dmaengine.h>
  #include <linux/hardirq.h>
  #include <linux/spinlock.h>
  #include <linux/percpu.h>
  #include <linux/rcupdate.h>
  #include <linux/mutex.h>
  #include <linux/jiffies.h>
  #include <linux/rculist.h>
  #include <linux/idr.h>
  #include <linux/slab.h>
  
  static DEFINE_MUTEX(dma_list_mutex);
  static LIST_HEAD(dma_device_list);
  static long dmaengine_ref_count;
  static struct idr dma_idr;
  
  /* --- sysfs implementation --- */
  
  /**
   * dev_to_dma_chan - convert a device pointer to the its sysfs container object
   * @dev - device node
   *
   * Must be called under dma_list_mutex
   */
  static struct dma_chan *dev_to_dma_chan(struct device *dev)
  {
  	struct dma_chan_dev *chan_dev;
  
  	chan_dev = container_of(dev, typeof(*chan_dev), device);
  	return chan_dev->chan;
  }
  
  static ssize_t show_memcpy_count(struct device *dev, struct device_attribute *attr, char *buf)
  {
  	struct dma_chan *chan;
  	unsigned long count = 0;
  	int i;
  	int err;
  
  	mutex_lock(&dma_list_mutex);
  	chan = dev_to_dma_chan(dev);
  	if (chan) {
  		for_each_possible_cpu(i)
  			count += per_cpu_ptr(chan->local, i)->memcpy_count;
  		err = sprintf(buf, "%lu\n", count);
  	} else
  		err = -ENODEV;
  	mutex_unlock(&dma_list_mutex);
  
  	return err;
  }
  
  static ssize_t show_bytes_transferred(struct device *dev, struct device_attribute *attr,
  				      char *buf)
  {
  	struct dma_chan *chan;
  	unsigned long count = 0;
  	int i;
  	int err;
  
  	mutex_lock(&dma_list_mutex);
  	chan = dev_to_dma_chan(dev);
  	if (chan) {
  		for_each_possible_cpu(i)
  			count += per_cpu_ptr(chan->local, i)->bytes_transferred;
  		err = sprintf(buf, "%lu\n", count);
  	} else
  		err = -ENODEV;
  	mutex_unlock(&dma_list_mutex);
  
  	return err;
  }
  
  static ssize_t show_in_use(struct device *dev, struct device_attribute *attr, char *buf)
  {
  	struct dma_chan *chan;
  	int err;
  
  	mutex_lock(&dma_list_mutex);
  	chan = dev_to_dma_chan(dev);
  	if (chan)
  		err = sprintf(buf, "%d\n", chan->client_count);
  	else
  		err = -ENODEV;
  	mutex_unlock(&dma_list_mutex);
  
  	return err;
  }
  
  static struct device_attribute dma_attrs[] = {
  	__ATTR(memcpy_count, S_IRUGO, show_memcpy_count, NULL),
  	__ATTR(bytes_transferred, S_IRUGO, show_bytes_transferred, NULL),
  	__ATTR(in_use, S_IRUGO, show_in_use, NULL),
  	__ATTR_NULL
  };
  
  static void chan_dev_release(struct device *dev)
  {
  	struct dma_chan_dev *chan_dev;
  
  	chan_dev = container_of(dev, typeof(*chan_dev), device);
  	if (atomic_dec_and_test(chan_dev->idr_ref)) {
  		mutex_lock(&dma_list_mutex);
  		idr_remove(&dma_idr, chan_dev->dev_id);
  		mutex_unlock(&dma_list_mutex);
  		kfree(chan_dev->idr_ref);
  	}
  	kfree(chan_dev);
  }
  
  static struct class dma_devclass = {
  	.name		= "dma",
  	.dev_attrs	= dma_attrs,
  	.dev_release	= chan_dev_release,
  };
  
  /* --- client and device registration --- */
  
  #define dma_device_satisfies_mask(device, mask) \
  	__dma_device_satisfies_mask((device), &(mask))
  static int
  __dma_device_satisfies_mask(struct dma_device *device, dma_cap_mask_t *want)
  {
  	dma_cap_mask_t has;
  
  	bitmap_and(has.bits, want->bits, device->cap_mask.bits,
  		DMA_TX_TYPE_END);
  	return bitmap_equal(want->bits, has.bits, DMA_TX_TYPE_END);
  }
  
  static struct module *dma_chan_to_owner(struct dma_chan *chan)
  {
  	return chan->device->dev->driver->owner;
  }
  
  /**
   * balance_ref_count - catch up the channel reference count
   * @chan - channel to balance ->client_count versus dmaengine_ref_count
   *
   * balance_ref_count must be called under dma_list_mutex
   */
  static void balance_ref_count(struct dma_chan *chan)
  {
  	struct module *owner = dma_chan_to_owner(chan);
  
  	while (chan->client_count < dmaengine_ref_count) {
  		__module_get(owner);
  		chan->client_count++;
  	}
  }
  
  /**
   * dma_chan_get - try to grab a dma channel's parent driver module
   * @chan - channel to grab
   *
   * Must be called under dma_list_mutex
   */
  static int dma_chan_get(struct dma_chan *chan)
  {
  	int err = -ENODEV;
  	struct module *owner = dma_chan_to_owner(chan);
  
  	if (chan->client_count) {
  		__module_get(owner);
  		err = 0;
  	} else if (try_module_get(owner))
  		err = 0;
  
  	if (err == 0)
  		chan->client_count++;
  
  	/* allocate upon first client reference */
  	if (chan->client_count == 1 && err == 0) {
  		int desc_cnt = chan->device->device_alloc_chan_resources(chan);
  
  		if (desc_cnt < 0) {
  			err = desc_cnt;
  			chan->client_count = 0;
  			module_put(owner);
  		} else if (!dma_has_cap(DMA_PRIVATE, chan->device->cap_mask))
  			balance_ref_count(chan);
  	}
  
  	return err;
  }
  
  /**
   * dma_chan_put - drop a reference to a dma channel's parent driver module
   * @chan - channel to release
   *
   * Must be called under dma_list_mutex
   */
  static void dma_chan_put(struct dma_chan *chan)
  {
  	if (!chan->client_count)
  		return; /* this channel failed alloc_chan_resources */
  	chan->client_count--;
  	module_put(dma_chan_to_owner(chan));
  	if (chan->client_count == 0)
  		chan->device->device_free_chan_resources(chan);
  }
  
  enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie)
  {
  	enum dma_status status;
  	unsigned long dma_sync_wait_timeout = jiffies + msecs_to_jiffies(5000);
  
  	dma_async_issue_pending(chan);
  	do {
  		status = dma_async_is_tx_complete(chan, cookie, NULL, NULL);
  		if (time_after_eq(jiffies, dma_sync_wait_timeout)) {
  			printk(KERN_ERR "dma_sync_wait_timeout!\n");
  			return DMA_ERROR;
  		}
  	} while (status == DMA_IN_PROGRESS);
  
  	return status;
  }
  EXPORT_SYMBOL(dma_sync_wait);
  
  /**
   * dma_cap_mask_all - enable iteration over all operation types
   */
  static dma_cap_mask_t dma_cap_mask_all;
  
  /**
   * dma_chan_tbl_ent - tracks channel allocations per core/operation
   * @chan - associated channel for this entry
   */
  struct dma_chan_tbl_ent {
  	struct dma_chan *chan;
  };
  
  /**
   * channel_table - percpu lookup table for memory-to-memory offload providers
   */
  static struct dma_chan_tbl_ent __percpu *channel_table[DMA_TX_TYPE_END];
  
  static int __init dma_channel_table_init(void)
  {
  	enum dma_transaction_type cap;
  	int err = 0;
  
  	bitmap_fill(dma_cap_mask_all.bits, DMA_TX_TYPE_END);
  
  	/* 'interrupt', 'private', and 'slave' are channel capabilities,
  	 * but are not associated with an operation so they do not need
  	 * an entry in the channel_table
  	 */
  	clear_bit(DMA_INTERRUPT, dma_cap_mask_all.bits);
  	clear_bit(DMA_PRIVATE, dma_cap_mask_all.bits);
  	clear_bit(DMA_SLAVE, dma_cap_mask_all.bits);
  
  	for_each_dma_cap_mask(cap, dma_cap_mask_all) {
  		channel_table[cap] = alloc_percpu(struct dma_chan_tbl_ent);
  		if (!channel_table[cap]) {
  			err = -ENOMEM;
  			break;
  		}
  	}
  
  	if (err) {
  		pr_err("dmaengine: initialization failure\n");
  		for_each_dma_cap_mask(cap, dma_cap_mask_all)
  			if (channel_table[cap])
  				free_percpu(channel_table[cap]);
  	}
  
  	return err;
  }
  arch_initcall(dma_channel_table_init);
  
  /**
   * dma_find_channel - find a channel to carry out the operation
   * @tx_type: transaction type
   */
  struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type)
  {
  	return this_cpu_read(channel_table[tx_type]->chan);
  }
  EXPORT_SYMBOL(dma_find_channel);
  
  /**
   * dma_issue_pending_all - flush all pending operations across all channels
   */
  void dma_issue_pending_all(void)
  {
  	struct dma_device *device;
  	struct dma_chan *chan;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(device, &dma_device_list, global_node) {
  		if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
  			continue;
  		list_for_each_entry(chan, &device->channels, device_node)
  			if (chan->client_count)
  				device->device_issue_pending(chan);
  	}
  	rcu_read_unlock();
  }
  EXPORT_SYMBOL(dma_issue_pending_all);
  
  /**
   * nth_chan - returns the nth channel of the given capability
   * @cap: capability to match
   * @n: nth channel desired
   *
   * Defaults to returning the channel with the desired capability and the
   * lowest reference count when 'n' cannot be satisfied.  Must be called
   * under dma_list_mutex.
   */
  static struct dma_chan *nth_chan(enum dma_transaction_type cap, int n)
  {
  	struct dma_device *device;
  	struct dma_chan *chan;
  	struct dma_chan *ret = NULL;
  	struct dma_chan *min = NULL;
  
  	list_for_each_entry(device, &dma_device_list, global_node) {
  		if (!dma_has_cap(cap, device->cap_mask) ||
  		    dma_has_cap(DMA_PRIVATE, device->cap_mask))
  			continue;
  		list_for_each_entry(chan, &device->channels, device_node) {
  			if (!chan->client_count)
  				continue;
  			if (!min)
  				min = chan;
  			else if (chan->table_count < min->table_count)
  				min = chan;
  
  			if (n-- == 0) {
  				ret = chan;
  				break; /* done */
  			}
  		}
  		if (ret)
  			break; /* done */
  	}
  
  	if (!ret)
  		ret = min;
  
  	if (ret)
  		ret->table_count++;
  
  	return ret;
  }
  
  /**
   * dma_channel_rebalance - redistribute the available channels
   *
   * Optimize for cpu isolation (each cpu gets a dedicated channel for an
   * operation type) in the SMP case,  and operation isolation (avoid
   * multi-tasking channels) in the non-SMP case.  Must be called under
   * dma_list_mutex.
   */
  static void dma_channel_rebalance(void)
  {
  	struct dma_chan *chan;
  	struct dma_device *device;
  	int cpu;
  	int cap;
  	int n;
  
  	/* undo the last distribution */
  	for_each_dma_cap_mask(cap, dma_cap_mask_all)
  		for_each_possible_cpu(cpu)
  			per_cpu_ptr(channel_table[cap], cpu)->chan = NULL;
  
  	list_for_each_entry(device, &dma_device_list, global_node) {
  		if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
  			continue;
  		list_for_each_entry(chan, &device->channels, device_node)
  			chan->table_count = 0;
  	}
  
  	/* don't populate the channel_table if no clients are available */
  	if (!dmaengine_ref_count)
  		return;
  
  	/* redistribute available channels */
  	n = 0;
  	for_each_dma_cap_mask(cap, dma_cap_mask_all)
  		for_each_online_cpu(cpu) {
  			if (num_possible_cpus() > 1)
  				chan = nth_chan(cap, n++);
  			else
  				chan = nth_chan(cap, -1);
  
  			per_cpu_ptr(channel_table[cap], cpu)->chan = chan;
  		}
  }
  
  static struct dma_chan *private_candidate(dma_cap_mask_t *mask, struct dma_device *dev,
  					  dma_filter_fn fn, void *fn_param)
  {
  	struct dma_chan *chan;
  
  	if (!__dma_device_satisfies_mask(dev, mask)) {
  		pr_debug("%s: wrong capabilities\n", __func__);
  		return NULL;
  	}
  	/* devices with multiple channels need special handling as we need to
  	 * ensure that all channels are either private or public.
  	 */
  	if (dev->chancnt > 1 && !dma_has_cap(DMA_PRIVATE, dev->cap_mask))
  		list_for_each_entry(chan, &dev->channels, device_node) {
  			/* some channels are already publicly allocated */
  			if (chan->client_count)
  				return NULL;
  		}
  
  	list_for_each_entry(chan, &dev->channels, device_node) {
  		if (chan->client_count) {
  			pr_debug("%s: %s busy\n",
  				 __func__, dma_chan_name(chan));
  			continue;
  		}
  		if (fn && !fn(chan, fn_param)) {
  			pr_debug("%s: %s filter said false\n",
  				 __func__, dma_chan_name(chan));
  			continue;
  		}
  		return chan;
  	}
  
  	return NULL;
  }
  
  /**
   * dma_request_channel - try to allocate an exclusive channel
   * @mask: capabilities that the channel must satisfy
   * @fn: optional callback to disposition available channels
   * @fn_param: opaque parameter to pass to dma_filter_fn
   */
  struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param)
  {
  	struct dma_device *device, *_d;
  	struct dma_chan *chan = NULL;
  	int err;
  
  	/* Find a channel */
  	mutex_lock(&dma_list_mutex);
  	list_for_each_entry_safe(device, _d, &dma_device_list, global_node) {
  		chan = private_candidate(mask, device, fn, fn_param);
  		if (chan) {
  			/* Found a suitable channel, try to grab, prep, and
  			 * return it.  We first set DMA_PRIVATE to disable
  			 * balance_ref_count as this channel will not be
  			 * published in the general-purpose allocator
  			 */
  			dma_cap_set(DMA_PRIVATE, device->cap_mask);
  			device->privatecnt++;
  			err = dma_chan_get(chan);
  
  			if (err == -ENODEV) {
  				pr_debug("%s: %s module removed\n", __func__,
  					 dma_chan_name(chan));
  				list_del_rcu(&device->global_node);
  			} else if (err)
  				pr_err("dmaengine: failed to get %s: (%d)\n",
  				       dma_chan_name(chan), err);
  			else
  				break;
  			if (--device->privatecnt == 0)
  				dma_cap_clear(DMA_PRIVATE, device->cap_mask);
  			chan->private = NULL;
  			chan = NULL;
  		}
  	}
  	mutex_unlock(&dma_list_mutex);
  
  	pr_debug("%s: %s (%s)\n", __func__, chan ? "success" : "fail",
  		 chan ? dma_chan_name(chan) : NULL);
  
  	return chan;
  }
  EXPORT_SYMBOL_GPL(__dma_request_channel);
  
  void dma_release_channel(struct dma_chan *chan)
  {
  	mutex_lock(&dma_list_mutex);
  	WARN_ONCE(chan->client_count != 1,
  		  "chan reference count %d != 1\n", chan->client_count);
  	dma_chan_put(chan);
  	/* drop PRIVATE cap enabled by __dma_request_channel() */
  	if (--chan->device->privatecnt == 0)
  		dma_cap_clear(DMA_PRIVATE, chan->device->cap_mask);
  	chan->private = NULL;
  	mutex_unlock(&dma_list_mutex);
  }
  EXPORT_SYMBOL_GPL(dma_release_channel);
  
  /**
   * dmaengine_get - register interest in dma_channels
   */
  void dmaengine_get(void)
  {
  	struct dma_device *device, *_d;
  	struct dma_chan *chan;
  	int err;
  
  	mutex_lock(&dma_list_mutex);
  	dmaengine_ref_count++;
  
  	/* try to grab channels */
  	list_for_each_entry_safe(device, _d, &dma_device_list, global_node) {
  		if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
  			continue;
  		list_for_each_entry(chan, &device->channels, device_node) {
  			err = dma_chan_get(chan);
  			if (err == -ENODEV) {
  				/* module removed before we could use it */
  				list_del_rcu(&device->global_node);
  				break;
  			} else if (err)
  				pr_err("dmaengine: failed to get %s: (%d)\n",
  				       dma_chan_name(chan), err);
  		}
  	}
  
  	/* if this is the first reference and there were channels
  	 * waiting we need to rebalance to get those channels
  	 * incorporated into the channel table
  	 */
  	if (dmaengine_ref_count == 1)
  		dma_channel_rebalance();
  	mutex_unlock(&dma_list_mutex);
  }
  EXPORT_SYMBOL(dmaengine_get);
  
  /**
   * dmaengine_put - let dma drivers be removed when ref_count == 0
   */
  void dmaengine_put(void)
  {
  	struct dma_device *device;
  	struct dma_chan *chan;
  
  	mutex_lock(&dma_list_mutex);
  	dmaengine_ref_count--;
  	BUG_ON(dmaengine_ref_count < 0);
  	/* drop channel references */
  	list_for_each_entry(device, &dma_device_list, global_node) {
  		if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
  			continue;
  		list_for_each_entry(chan, &device->channels, device_node)
  			dma_chan_put(chan);
  	}
  	mutex_unlock(&dma_list_mutex);
  }
  EXPORT_SYMBOL(dmaengine_put);
  
  static bool device_has_all_tx_types(struct dma_device *device)
  {
  	/* A device that satisfies this test has channels that will never cause
  	 * an async_tx channel switch event as all possible operation types can
  	 * be handled.
  	 */
  	#ifdef CONFIG_ASYNC_TX_DMA
  	if (!dma_has_cap(DMA_INTERRUPT, device->cap_mask))
  		return false;
  	#endif
  
  	#if defined(CONFIG_ASYNC_MEMCPY) || defined(CONFIG_ASYNC_MEMCPY_MODULE)
  	if (!dma_has_cap(DMA_MEMCPY, device->cap_mask))
  		return false;
  	#endif
  
  	#if defined(CONFIG_ASYNC_MEMSET) || defined(CONFIG_ASYNC_MEMSET_MODULE)
  	if (!dma_has_cap(DMA_MEMSET, device->cap_mask))
  		return false;
  	#endif
  
  	#if defined(CONFIG_ASYNC_XOR) || defined(CONFIG_ASYNC_XOR_MODULE)
  	if (!dma_has_cap(DMA_XOR, device->cap_mask))
  		return false;
  
  	#ifndef CONFIG_ASYNC_TX_DISABLE_XOR_VAL_DMA
  	if (!dma_has_cap(DMA_XOR_VAL, device->cap_mask))
  		return false;
  	#endif
  	#endif
  
  	#if defined(CONFIG_ASYNC_PQ) || defined(CONFIG_ASYNC_PQ_MODULE)
  	if (!dma_has_cap(DMA_PQ, device->cap_mask))
  		return false;
  
  	#ifndef CONFIG_ASYNC_TX_DISABLE_PQ_VAL_DMA
  	if (!dma_has_cap(DMA_PQ_VAL, device->cap_mask))
  		return false;
  	#endif
  	#endif
  
  	return true;
  }
  
  static int get_dma_id(struct dma_device *device)
  {
  	int rc;
  
   idr_retry:
  	if (!idr_pre_get(&dma_idr, GFP_KERNEL))
  		return -ENOMEM;
  	mutex_lock(&dma_list_mutex);
  	rc = idr_get_new(&dma_idr, NULL, &device->dev_id);
  	mutex_unlock(&dma_list_mutex);
  	if (rc == -EAGAIN)
  		goto idr_retry;
  	else if (rc != 0)
  		return rc;
  
  	return 0;
  }
  
  /**
   * dma_async_device_register - registers DMA devices found
   * @device: &dma_device
   */
  int dma_async_device_register(struct dma_device *device)
  {
  	int chancnt = 0, rc;
  	struct dma_chan* chan;
  	atomic_t *idr_ref;
  
  	if (!device)
  		return -ENODEV;
  
  	/* validate device routines */
  	BUG_ON(dma_has_cap(DMA_MEMCPY, device->cap_mask) &&
  		!device->device_prep_dma_memcpy);
  	BUG_ON(dma_has_cap(DMA_XOR, device->cap_mask) &&
  		!device->device_prep_dma_xor);
  	BUG_ON(dma_has_cap(DMA_XOR_VAL, device->cap_mask) &&
  		!device->device_prep_dma_xor_val);
  	BUG_ON(dma_has_cap(DMA_PQ, device->cap_mask) &&
  		!device->device_prep_dma_pq);
  	BUG_ON(dma_has_cap(DMA_PQ_VAL, device->cap_mask) &&
  		!device->device_prep_dma_pq_val);
  	BUG_ON(dma_has_cap(DMA_MEMSET, device->cap_mask) &&
  		!device->device_prep_dma_memset);
  	BUG_ON(dma_has_cap(DMA_INTERRUPT, device->cap_mask) &&
  		!device->device_prep_dma_interrupt);
  	BUG_ON(dma_has_cap(DMA_SLAVE, device->cap_mask) &&
  		!device->device_prep_slave_sg);
  	BUG_ON(dma_has_cap(DMA_SLAVE, device->cap_mask) &&
  		!device->device_terminate_all);
  
  	BUG_ON(!device->device_alloc_chan_resources);
  	BUG_ON(!device->device_free_chan_resources);
  	BUG_ON(!device->device_is_tx_complete);
  	BUG_ON(!device->device_issue_pending);
  	BUG_ON(!device->dev);
  
  	/* note: this only matters in the
  	 * CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH=y case
  	 */
  	if (device_has_all_tx_types(device))
  		dma_cap_set(DMA_ASYNC_TX, device->cap_mask);
  
  	idr_ref = kmalloc(sizeof(*idr_ref), GFP_KERNEL);
  	if (!idr_ref)
  		return -ENOMEM;
  	rc = get_dma_id(device);
  	if (rc != 0) {
  		kfree(idr_ref);
  		return rc;
  	}
  
  	atomic_set(idr_ref, 0);
  
  	/* represent channels in sysfs. Probably want devs too */
  	list_for_each_entry(chan, &device->channels, device_node) {
  		rc = -ENOMEM;
  		chan->local = alloc_percpu(typeof(*chan->local));
  		if (chan->local == NULL)
  			goto err_out;
  		chan->dev = kzalloc(sizeof(*chan->dev), GFP_KERNEL);
  		if (chan->dev == NULL) {
  			free_percpu(chan->local);
  			chan->local = NULL;
  			goto err_out;
  		}
  
  		chan->chan_id = chancnt++;
  		chan->dev->device.class = &dma_devclass;
  		chan->dev->device.parent = device->dev;
  		chan->dev->chan = chan;
  		chan->dev->idr_ref = idr_ref;
  		chan->dev->dev_id = device->dev_id;
  		atomic_inc(idr_ref);
  		dev_set_name(&chan->dev->device, "dma%dchan%d",
  			     device->dev_id, chan->chan_id);
  
  		rc = device_register(&chan->dev->device);
  		if (rc) {
  			free_percpu(chan->local);
  			chan->local = NULL;
  			kfree(chan->dev);
  			atomic_dec(idr_ref);
  			goto err_out;
  		}
  		chan->client_count = 0;
  	}
  	device->chancnt = chancnt;
  
  	mutex_lock(&dma_list_mutex);
  	/* take references on public channels */
  	if (dmaengine_ref_count && !dma_has_cap(DMA_PRIVATE, device->cap_mask))
  		list_for_each_entry(chan, &device->channels, device_node) {
  			/* if clients are already waiting for channels we need
  			 * to take references on their behalf
  			 */
  			if (dma_chan_get(chan) == -ENODEV) {
  				/* note we can only get here for the first
  				 * channel as the remaining channels are
  				 * guaranteed to get a reference
  				 */
  				rc = -ENODEV;
  				mutex_unlock(&dma_list_mutex);
  				goto err_out;
  			}
  		}
  	list_add_tail_rcu(&device->global_node, &dma_device_list);
  	if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
  		device->privatecnt++;	/* Always private */
  	dma_channel_rebalance();
  	mutex_unlock(&dma_list_mutex);
  
  	return 0;
  
  err_out:
  	/* if we never registered a channel just release the idr */
  	if (atomic_read(idr_ref) == 0) {
  		mutex_lock(&dma_list_mutex);
  		idr_remove(&dma_idr, device->dev_id);
  		mutex_unlock(&dma_list_mutex);
  		kfree(idr_ref);
  		return rc;
  	}
  
  	list_for_each_entry(chan, &device->channels, device_node) {
  		if (chan->local == NULL)
  			continue;
  		mutex_lock(&dma_list_mutex);
  		chan->dev->chan = NULL;
  		mutex_unlock(&dma_list_mutex);
  		device_unregister(&chan->dev->device);
  		free_percpu(chan->local);
  	}
  	return rc;
  }
  EXPORT_SYMBOL(dma_async_device_register);
  
  /**
   * dma_async_device_unregister - unregister a DMA device
   * @device: &dma_device
   *
   * This routine is called by dma driver exit routines, dmaengine holds module
   * references to prevent it being called while channels are in use.
   */
  void dma_async_device_unregister(struct dma_device *device)
  {
  	struct dma_chan *chan;
  
  	mutex_lock(&dma_list_mutex);
  	list_del_rcu(&device->global_node);
  	dma_channel_rebalance();
  	mutex_unlock(&dma_list_mutex);
  
  	list_for_each_entry(chan, &device->channels, device_node) {
  		WARN_ONCE(chan->client_count,
  			  "%s called while %d clients hold a reference\n",
  			  __func__, chan->client_count);
  		mutex_lock(&dma_list_mutex);
  		chan->dev->chan = NULL;
  		mutex_unlock(&dma_list_mutex);
  		device_unregister(&chan->dev->device);
  		free_percpu(chan->local);
  	}
  }
  EXPORT_SYMBOL(dma_async_device_unregister);
  
  /**
   * dma_async_memcpy_buf_to_buf - offloaded copy between virtual addresses
   * @chan: DMA channel to offload copy to
   * @dest: destination address (virtual)
   * @src: source address (virtual)
   * @len: length
   *
   * Both @dest and @src must be mappable to a bus address according to the
   * DMA mapping API rules for streaming mappings.
   * Both @dest and @src must stay memory resident (kernel memory or locked
   * user space pages).
   */
  dma_cookie_t
  dma_async_memcpy_buf_to_buf(struct dma_chan *chan, void *dest,
  			void *src, size_t len)
  {
  	struct dma_device *dev = chan->device;
  	struct dma_async_tx_descriptor *tx;
  	dma_addr_t dma_dest, dma_src;
  	dma_cookie_t cookie;
  	unsigned long flags;
  
  	dma_src = dma_map_single(dev->dev, src, len, DMA_TO_DEVICE);
  	dma_dest = dma_map_single(dev->dev, dest, len, DMA_FROM_DEVICE);
  	flags = DMA_CTRL_ACK |
  		DMA_COMPL_SRC_UNMAP_SINGLE |
  		DMA_COMPL_DEST_UNMAP_SINGLE;
  	tx = dev->device_prep_dma_memcpy(chan, dma_dest, dma_src, len, flags);
  
  	if (!tx) {
  		dma_unmap_single(dev->dev, dma_src, len, DMA_TO_DEVICE);
  		dma_unmap_single(dev->dev, dma_dest, len, DMA_FROM_DEVICE);
  		return -ENOMEM;
  	}
  
  	tx->callback = NULL;
  	cookie = tx->tx_submit(tx);
  
  	preempt_disable();
  	__this_cpu_add(chan->local->bytes_transferred, len);
  	__this_cpu_inc(chan->local->memcpy_count);
  	preempt_enable();
  
  	return cookie;
  }
  EXPORT_SYMBOL(dma_async_memcpy_buf_to_buf);
  
  /**
   * dma_async_memcpy_buf_to_pg - offloaded copy from address to page
   * @chan: DMA channel to offload copy to
   * @page: destination page
   * @offset: offset in page to copy to
   * @kdata: source address (virtual)
   * @len: length
   *
   * Both @page/@offset and @kdata must be mappable to a bus address according
   * to the DMA mapping API rules for streaming mappings.
   * Both @page/@offset and @kdata must stay memory resident (kernel memory or
   * locked user space pages)
   */
  dma_cookie_t
  dma_async_memcpy_buf_to_pg(struct dma_chan *chan, struct page *page,
  			unsigned int offset, void *kdata, size_t len)
  {
  	struct dma_device *dev = chan->device;
  	struct dma_async_tx_descriptor *tx;
  	dma_addr_t dma_dest, dma_src;
  	dma_cookie_t cookie;
  	unsigned long flags;
  
  	dma_src = dma_map_single(dev->dev, kdata, len, DMA_TO_DEVICE);
  	dma_dest = dma_map_page(dev->dev, page, offset, len, DMA_FROM_DEVICE);
  	flags = DMA_CTRL_ACK | DMA_COMPL_SRC_UNMAP_SINGLE;
  	tx = dev->device_prep_dma_memcpy(chan, dma_dest, dma_src, len, flags);
  
  	if (!tx) {
  		dma_unmap_single(dev->dev, dma_src, len, DMA_TO_DEVICE);
  		dma_unmap_page(dev->dev, dma_dest, len, DMA_FROM_DEVICE);
  		return -ENOMEM;
  	}
  
  	tx->callback = NULL;
  	cookie = tx->tx_submit(tx);
  
  	preempt_disable();
  	__this_cpu_add(chan->local->bytes_transferred, len);
  	__this_cpu_inc(chan->local->memcpy_count);
  	preempt_enable();
  
  	return cookie;
  }
  EXPORT_SYMBOL(dma_async_memcpy_buf_to_pg);
  
  /**
   * dma_async_memcpy_pg_to_pg - offloaded copy from page to page
   * @chan: DMA channel to offload copy to
   * @dest_pg: destination page
   * @dest_off: offset in page to copy to
   * @src_pg: source page
   * @src_off: offset in page to copy from
   * @len: length
   *
   * Both @dest_page/@dest_off and @src_page/@src_off must be mappable to a bus
   * address according to the DMA mapping API rules for streaming mappings.
   * Both @dest_page/@dest_off and @src_page/@src_off must stay memory resident
   * (kernel memory or locked user space pages).
   */
  dma_cookie_t
  dma_async_memcpy_pg_to_pg(struct dma_chan *chan, struct page *dest_pg,
  	unsigned int dest_off, struct page *src_pg, unsigned int src_off,
  	size_t len)
  {
  	struct dma_device *dev = chan->device;
  	struct dma_async_tx_descriptor *tx;
  	dma_addr_t dma_dest, dma_src;
  	dma_cookie_t cookie;
  	unsigned long flags;
  
  	dma_src = dma_map_page(dev->dev, src_pg, src_off, len, DMA_TO_DEVICE);
  	dma_dest = dma_map_page(dev->dev, dest_pg, dest_off, len,
  				DMA_FROM_DEVICE);
  	flags = DMA_CTRL_ACK;
  	tx = dev->device_prep_dma_memcpy(chan, dma_dest, dma_src, len, flags);
  
  	if (!tx) {
  		dma_unmap_page(dev->dev, dma_src, len, DMA_TO_DEVICE);
  		dma_unmap_page(dev->dev, dma_dest, len, DMA_FROM_DEVICE);
  		return -ENOMEM;
  	}
  
  	tx->callback = NULL;
  	cookie = tx->tx_submit(tx);
  
  	preempt_disable();
  	__this_cpu_add(chan->local->bytes_transferred, len);
  	__this_cpu_inc(chan->local->memcpy_count);
  	preempt_enable();
  
  	return cookie;
  }
  EXPORT_SYMBOL(dma_async_memcpy_pg_to_pg);
  
  void dma_async_tx_descriptor_init(struct dma_async_tx_descriptor *tx,
  	struct dma_chan *chan)
  {
  	tx->chan = chan;
  	spin_lock_init(&tx->lock);
  }
  EXPORT_SYMBOL(dma_async_tx_descriptor_init);
  
  /* dma_wait_for_async_tx - spin wait for a transaction to complete
   * @tx: in-flight transaction to wait on
   */
  enum dma_status
  dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
  {
  	unsigned long dma_sync_wait_timeout = jiffies + msecs_to_jiffies(5000);
  
  	if (!tx)
  		return DMA_SUCCESS;
  
  	while (tx->cookie == -EBUSY) {
  		if (time_after_eq(jiffies, dma_sync_wait_timeout)) {
  			pr_err("%s timeout waiting for descriptor submission\n",
  				__func__);
  			return DMA_ERROR;
  		}
  		cpu_relax();
  	}
  	return dma_sync_wait(tx->chan, tx->cookie);
  }
  EXPORT_SYMBOL_GPL(dma_wait_for_async_tx);
  
  /* dma_run_dependencies - helper routine for dma drivers to process
   *	(start) dependent operations on their target channel
   * @tx: transaction with dependencies
   */
  void dma_run_dependencies(struct dma_async_tx_descriptor *tx)
  {
  	struct dma_async_tx_descriptor *dep = tx->next;
  	struct dma_async_tx_descriptor *dep_next;
  	struct dma_chan *chan;
  
  	if (!dep)
  		return;
  
  	/* we'll submit tx->next now, so clear the link */
  	tx->next = NULL;
  	chan = dep->chan;
  
  	/* keep submitting up until a channel switch is detected
  	 * in that case we will be called again as a result of
  	 * processing the interrupt from async_tx_channel_switch
  	 */
  	for (; dep; dep = dep_next) {
  		spin_lock_bh(&dep->lock);
  		dep->parent = NULL;
  		dep_next = dep->next;
  		if (dep_next && dep_next->chan == chan)
  			dep->next = NULL; /* ->next will be submitted */
  		else
  			dep_next = NULL; /* submit current dep and terminate */
  		spin_unlock_bh(&dep->lock);
  
  		dep->tx_submit(dep);
  	}
  
  	chan->device->device_issue_pending(chan);
  }
  EXPORT_SYMBOL_GPL(dma_run_dependencies);
  
  static int __init dma_bus_init(void)
  {
  	idr_init(&dma_idr);
  	mutex_init(&dma_list_mutex);
  	return class_register(&dma_devclass);
  }
  arch_initcall(dma_bus_init);
  
  
  