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6508871edd
Fix kernel-doc warnings in drivers/dma/: - use correct function & parameter names - add descriptions where omitted Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: David S. Miller <davem@davemloft.net>
413 lines
12 KiB
C
413 lines
12 KiB
C
/*
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* Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 59
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* Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* The full GNU General Public License is included in this distribution in the
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* file called COPYING.
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*/
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/*
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* This code implements the DMA subsystem. It provides a HW-neutral interface
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* for other kernel code to use asynchronous memory copy capabilities,
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* if present, and allows different HW DMA drivers to register as providing
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* this capability.
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*
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* Due to the fact we are accelerating what is already a relatively fast
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* operation, the code goes to great lengths to avoid additional overhead,
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* such as locking.
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*
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* LOCKING:
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*
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* The subsystem keeps two global lists, dma_device_list and dma_client_list.
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* Both of these are protected by a mutex, dma_list_mutex.
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*
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* Each device has a channels list, which runs unlocked but is never modified
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* once the device is registered, it's just setup by the driver.
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*
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* Each client has a channels list, it's only modified under the client->lock
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* and in an RCU callback, so it's safe to read under rcu_read_lock().
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*
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* Each device has a kref, which is initialized to 1 when the device is
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* registered. A kref_put is done for each class_device registered. When the
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* class_device is released, the coresponding kref_put is done in the release
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* method. Every time one of the device's channels is allocated to a client,
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* a kref_get occurs. When the channel is freed, the coresponding kref_put
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* happens. The device's release function does a completion, so
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* unregister_device does a remove event, class_device_unregister, a kref_put
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* for the first reference, then waits on the completion for all other
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* references to finish.
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*
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* Each channel has an open-coded implementation of Rusty Russell's "bigref,"
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* with a kref and a per_cpu local_t. A single reference is set when on an
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* ADDED event, and removed with a REMOVE event. Net DMA client takes an
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* extra reference per outstanding transaction. The relase function does a
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* kref_put on the device. -ChrisL
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*/
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/device.h>
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#include <linux/dmaengine.h>
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#include <linux/hardirq.h>
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#include <linux/spinlock.h>
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#include <linux/percpu.h>
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#include <linux/rcupdate.h>
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#include <linux/mutex.h>
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static DEFINE_MUTEX(dma_list_mutex);
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static LIST_HEAD(dma_device_list);
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static LIST_HEAD(dma_client_list);
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/* --- sysfs implementation --- */
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static ssize_t show_memcpy_count(struct class_device *cd, char *buf)
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{
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struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
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unsigned long count = 0;
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int i;
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for_each_possible_cpu(i)
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count += per_cpu_ptr(chan->local, i)->memcpy_count;
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return sprintf(buf, "%lu\n", count);
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}
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static ssize_t show_bytes_transferred(struct class_device *cd, char *buf)
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{
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struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
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unsigned long count = 0;
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int i;
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for_each_possible_cpu(i)
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count += per_cpu_ptr(chan->local, i)->bytes_transferred;
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return sprintf(buf, "%lu\n", count);
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}
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static ssize_t show_in_use(struct class_device *cd, char *buf)
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{
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struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
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return sprintf(buf, "%d\n", (chan->client ? 1 : 0));
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}
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static struct class_device_attribute dma_class_attrs[] = {
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__ATTR(memcpy_count, S_IRUGO, show_memcpy_count, NULL),
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__ATTR(bytes_transferred, S_IRUGO, show_bytes_transferred, NULL),
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__ATTR(in_use, S_IRUGO, show_in_use, NULL),
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__ATTR_NULL
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};
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static void dma_async_device_cleanup(struct kref *kref);
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static void dma_class_dev_release(struct class_device *cd)
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{
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struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
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kref_put(&chan->device->refcount, dma_async_device_cleanup);
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}
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static struct class dma_devclass = {
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.name = "dma",
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.class_dev_attrs = dma_class_attrs,
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.release = dma_class_dev_release,
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};
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/* --- client and device registration --- */
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/**
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* dma_client_chan_alloc - try to allocate a channel to a client
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* @client: &dma_client
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*
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* Called with dma_list_mutex held.
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*/
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static struct dma_chan *dma_client_chan_alloc(struct dma_client *client)
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{
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struct dma_device *device;
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struct dma_chan *chan;
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unsigned long flags;
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int desc; /* allocated descriptor count */
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/* Find a channel, any DMA engine will do */
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list_for_each_entry(device, &dma_device_list, global_node) {
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list_for_each_entry(chan, &device->channels, device_node) {
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if (chan->client)
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continue;
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desc = chan->device->device_alloc_chan_resources(chan);
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if (desc >= 0) {
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kref_get(&device->refcount);
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kref_init(&chan->refcount);
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chan->slow_ref = 0;
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INIT_RCU_HEAD(&chan->rcu);
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chan->client = client;
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spin_lock_irqsave(&client->lock, flags);
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list_add_tail_rcu(&chan->client_node,
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&client->channels);
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spin_unlock_irqrestore(&client->lock, flags);
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return chan;
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}
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}
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}
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return NULL;
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}
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/**
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* dma_chan_cleanup - release a DMA channel's resources
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* @kref: kernel reference structure that contains the DMA channel device
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*/
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void dma_chan_cleanup(struct kref *kref)
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{
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struct dma_chan *chan = container_of(kref, struct dma_chan, refcount);
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chan->device->device_free_chan_resources(chan);
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chan->client = NULL;
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kref_put(&chan->device->refcount, dma_async_device_cleanup);
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}
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static void dma_chan_free_rcu(struct rcu_head *rcu)
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{
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struct dma_chan *chan = container_of(rcu, struct dma_chan, rcu);
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int bias = 0x7FFFFFFF;
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int i;
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for_each_possible_cpu(i)
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bias -= local_read(&per_cpu_ptr(chan->local, i)->refcount);
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atomic_sub(bias, &chan->refcount.refcount);
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kref_put(&chan->refcount, dma_chan_cleanup);
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}
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static void dma_client_chan_free(struct dma_chan *chan)
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{
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atomic_add(0x7FFFFFFF, &chan->refcount.refcount);
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chan->slow_ref = 1;
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call_rcu(&chan->rcu, dma_chan_free_rcu);
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}
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/**
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* dma_chans_rebalance - reallocate channels to clients
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*
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* When the number of DMA channel in the system changes,
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* channels need to be rebalanced among clients.
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*/
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static void dma_chans_rebalance(void)
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{
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struct dma_client *client;
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struct dma_chan *chan;
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unsigned long flags;
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mutex_lock(&dma_list_mutex);
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list_for_each_entry(client, &dma_client_list, global_node) {
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while (client->chans_desired > client->chan_count) {
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chan = dma_client_chan_alloc(client);
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if (!chan)
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break;
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client->chan_count++;
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client->event_callback(client,
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chan,
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DMA_RESOURCE_ADDED);
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}
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while (client->chans_desired < client->chan_count) {
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spin_lock_irqsave(&client->lock, flags);
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chan = list_entry(client->channels.next,
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struct dma_chan,
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client_node);
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list_del_rcu(&chan->client_node);
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spin_unlock_irqrestore(&client->lock, flags);
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client->chan_count--;
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client->event_callback(client,
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chan,
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DMA_RESOURCE_REMOVED);
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dma_client_chan_free(chan);
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}
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}
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mutex_unlock(&dma_list_mutex);
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}
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/**
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* dma_async_client_register - allocate and register a &dma_client
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* @event_callback: callback for notification of channel addition/removal
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*/
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struct dma_client *dma_async_client_register(dma_event_callback event_callback)
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{
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struct dma_client *client;
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client = kzalloc(sizeof(*client), GFP_KERNEL);
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if (!client)
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return NULL;
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INIT_LIST_HEAD(&client->channels);
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spin_lock_init(&client->lock);
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client->chans_desired = 0;
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client->chan_count = 0;
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client->event_callback = event_callback;
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mutex_lock(&dma_list_mutex);
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list_add_tail(&client->global_node, &dma_client_list);
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mutex_unlock(&dma_list_mutex);
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return client;
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}
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/**
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* dma_async_client_unregister - unregister a client and free the &dma_client
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* @client: &dma_client to free
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*
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* Force frees any allocated DMA channels, frees the &dma_client memory
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*/
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void dma_async_client_unregister(struct dma_client *client)
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{
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struct dma_chan *chan;
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if (!client)
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return;
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rcu_read_lock();
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list_for_each_entry_rcu(chan, &client->channels, client_node)
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dma_client_chan_free(chan);
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rcu_read_unlock();
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mutex_lock(&dma_list_mutex);
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list_del(&client->global_node);
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mutex_unlock(&dma_list_mutex);
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kfree(client);
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dma_chans_rebalance();
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}
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/**
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* dma_async_client_chan_request - request DMA channels
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* @client: &dma_client
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* @number: count of DMA channels requested
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*
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* Clients call dma_async_client_chan_request() to specify how many
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* DMA channels they need, 0 to free all currently allocated.
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* The resulting allocations/frees are indicated to the client via the
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* event callback.
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*/
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void dma_async_client_chan_request(struct dma_client *client,
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unsigned int number)
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{
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client->chans_desired = number;
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dma_chans_rebalance();
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}
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/**
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* dma_async_device_register - registers DMA devices found
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* @device: &dma_device
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*/
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int dma_async_device_register(struct dma_device *device)
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{
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static int id;
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int chancnt = 0;
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struct dma_chan* chan;
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if (!device)
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return -ENODEV;
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init_completion(&device->done);
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kref_init(&device->refcount);
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device->dev_id = id++;
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/* represent channels in sysfs. Probably want devs too */
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list_for_each_entry(chan, &device->channels, device_node) {
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chan->local = alloc_percpu(typeof(*chan->local));
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if (chan->local == NULL)
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continue;
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chan->chan_id = chancnt++;
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chan->class_dev.class = &dma_devclass;
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chan->class_dev.dev = NULL;
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snprintf(chan->class_dev.class_id, BUS_ID_SIZE, "dma%dchan%d",
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device->dev_id, chan->chan_id);
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kref_get(&device->refcount);
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class_device_register(&chan->class_dev);
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}
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mutex_lock(&dma_list_mutex);
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list_add_tail(&device->global_node, &dma_device_list);
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mutex_unlock(&dma_list_mutex);
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dma_chans_rebalance();
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return 0;
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}
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/**
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* dma_async_device_cleanup - function called when all references are released
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* @kref: kernel reference object
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*/
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static void dma_async_device_cleanup(struct kref *kref)
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{
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struct dma_device *device;
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device = container_of(kref, struct dma_device, refcount);
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complete(&device->done);
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}
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/**
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* dma_async_device_unregister - unregisters DMA devices
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* @device: &dma_device
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*/
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void dma_async_device_unregister(struct dma_device *device)
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{
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struct dma_chan *chan;
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unsigned long flags;
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mutex_lock(&dma_list_mutex);
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list_del(&device->global_node);
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mutex_unlock(&dma_list_mutex);
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list_for_each_entry(chan, &device->channels, device_node) {
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if (chan->client) {
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spin_lock_irqsave(&chan->client->lock, flags);
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list_del(&chan->client_node);
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chan->client->chan_count--;
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spin_unlock_irqrestore(&chan->client->lock, flags);
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chan->client->event_callback(chan->client,
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chan,
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DMA_RESOURCE_REMOVED);
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dma_client_chan_free(chan);
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}
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class_device_unregister(&chan->class_dev);
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}
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dma_chans_rebalance();
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kref_put(&device->refcount, dma_async_device_cleanup);
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wait_for_completion(&device->done);
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}
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static int __init dma_bus_init(void)
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{
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mutex_init(&dma_list_mutex);
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return class_register(&dma_devclass);
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}
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subsys_initcall(dma_bus_init);
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EXPORT_SYMBOL(dma_async_client_register);
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EXPORT_SYMBOL(dma_async_client_unregister);
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EXPORT_SYMBOL(dma_async_client_chan_request);
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EXPORT_SYMBOL(dma_async_memcpy_buf_to_buf);
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EXPORT_SYMBOL(dma_async_memcpy_buf_to_pg);
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EXPORT_SYMBOL(dma_async_memcpy_pg_to_pg);
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EXPORT_SYMBOL(dma_async_memcpy_complete);
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EXPORT_SYMBOL(dma_async_memcpy_issue_pending);
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EXPORT_SYMBOL(dma_async_device_register);
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EXPORT_SYMBOL(dma_async_device_unregister);
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EXPORT_SYMBOL(dma_chan_cleanup);
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