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[I/OAT]: DMA memcpy subsystem

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Provides an API for offloading memory copies to DMA devices

Signed-off-by: Chris Leech <christopher.leech@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Chris Leech
2006-05-23 17:18:44 -07:00
committed by David S. Miller
parent 427abfa28a
commit c13c8260da
6 changed files with 762 additions and 0 deletions
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drivers/dma/dmaengine.c Normal file
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/*
* 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 two global lists, dma_device_list and dma_client_list.
* Both of these are protected by a mutex, dma_list_mutex.
*
* 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.
*
* Each client has a channels list, it's only modified under the client->lock
* and in an RCU callback, so it's safe to read under rcu_read_lock().
*
* Each device has a kref, which is initialized to 1 when the device is
* registered. A kref_put is done for each class_device registered. When the
* class_device is released, the coresponding kref_put is done in the release
* method. Every time one of the device's channels is allocated to a client,
* a kref_get occurs. When the channel is freed, the coresponding kref_put
* happens. The device's release function does a completion, so
* unregister_device does a remove event, class_device_unregister, a kref_put
* for the first reference, then waits on the completion for all other
* references to finish.
*
* Each channel has an open-coded implementation of Rusty Russell's "bigref,"
* with a kref and a per_cpu local_t. A single reference is set when on an
* ADDED event, and removed with a REMOVE event. Net DMA client takes an
* extra reference per outstanding transaction. The relase function does a
* kref_put on the device. -ChrisL
*/
#include <linux/init.h>
#include <linux/module.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>
static DEFINE_MUTEX(dma_list_mutex);
static LIST_HEAD(dma_device_list);
static LIST_HEAD(dma_client_list);
/* --- sysfs implementation --- */
static ssize_t show_memcpy_count(struct class_device *cd, char *buf)
{
struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
unsigned long count = 0;
int i;
for_each_cpu(i)
count += per_cpu_ptr(chan->local, i)->memcpy_count;
return sprintf(buf, "%lu\n", count);
}
static ssize_t show_bytes_transferred(struct class_device *cd, char *buf)
{
struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
unsigned long count = 0;
int i;
for_each_cpu(i)
count += per_cpu_ptr(chan->local, i)->bytes_transferred;
return sprintf(buf, "%lu\n", count);
}
static ssize_t show_in_use(struct class_device *cd, char *buf)
{
struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
return sprintf(buf, "%d\n", (chan->client ? 1 : 0));
}
static struct class_device_attribute dma_class_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 dma_async_device_cleanup(struct kref *kref);
static void dma_class_dev_release(struct class_device *cd)
{
struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
kref_put(&chan->device->refcount, dma_async_device_cleanup);
}
static struct class dma_devclass = {
.name = "dma",
.class_dev_attrs = dma_class_attrs,
.release = dma_class_dev_release,
};
/* --- client and device registration --- */
/**
* dma_client_chan_alloc - try to allocate a channel to a client
* @client: &dma_client
*
* Called with dma_list_mutex held.
*/
static struct dma_chan *dma_client_chan_alloc(struct dma_client *client)
{
struct dma_device *device;
struct dma_chan *chan;
unsigned long flags;
int desc; /* allocated descriptor count */
/* Find a channel, any DMA engine will do */
list_for_each_entry(device, &dma_device_list, global_node) {
list_for_each_entry(chan, &device->channels, device_node) {
if (chan->client)
continue;
desc = chan->device->device_alloc_chan_resources(chan);
if (desc >= 0) {
kref_get(&device->refcount);
kref_init(&chan->refcount);
chan->slow_ref = 0;
INIT_RCU_HEAD(&chan->rcu);
chan->client = client;
spin_lock_irqsave(&client->lock, flags);
list_add_tail_rcu(&chan->client_node,
&client->channels);
spin_unlock_irqrestore(&client->lock, flags);
return chan;
}
}
}
return NULL;
}
/**
* dma_client_chan_free - release a DMA channel
* @chan: &dma_chan
*/
void dma_chan_cleanup(struct kref *kref)
{
struct dma_chan *chan = container_of(kref, struct dma_chan, refcount);
chan->device->device_free_chan_resources(chan);
chan->client = NULL;
kref_put(&chan->device->refcount, dma_async_device_cleanup);
}
static void dma_chan_free_rcu(struct rcu_head *rcu)
{
struct dma_chan *chan = container_of(rcu, struct dma_chan, rcu);
int bias = 0x7FFFFFFF;
int i;
for_each_cpu(i)
bias -= local_read(&per_cpu_ptr(chan->local, i)->refcount);
atomic_sub(bias, &chan->refcount.refcount);
kref_put(&chan->refcount, dma_chan_cleanup);
}
static void dma_client_chan_free(struct dma_chan *chan)
{
atomic_add(0x7FFFFFFF, &chan->refcount.refcount);
chan->slow_ref = 1;
call_rcu(&chan->rcu, dma_chan_free_rcu);
}
/**
* dma_chans_rebalance - reallocate channels to clients
*
* When the number of DMA channel in the system changes,
* channels need to be rebalanced among clients
*/
static void dma_chans_rebalance(void)
{
struct dma_client *client;
struct dma_chan *chan;
unsigned long flags;
mutex_lock(&dma_list_mutex);
list_for_each_entry(client, &dma_client_list, global_node) {
while (client->chans_desired > client->chan_count) {
chan = dma_client_chan_alloc(client);
if (!chan)
break;
client->chan_count++;
client->event_callback(client,
chan,
DMA_RESOURCE_ADDED);
}
while (client->chans_desired < client->chan_count) {
spin_lock_irqsave(&client->lock, flags);
chan = list_entry(client->channels.next,
struct dma_chan,
client_node);
list_del_rcu(&chan->client_node);
spin_unlock_irqrestore(&client->lock, flags);
client->chan_count--;
client->event_callback(client,
chan,
DMA_RESOURCE_REMOVED);
dma_client_chan_free(chan);
}
}
mutex_unlock(&dma_list_mutex);
}
/**
* dma_async_client_register - allocate and register a &dma_client
* @event_callback: callback for notification of channel addition/removal
*/
struct dma_client *dma_async_client_register(dma_event_callback event_callback)
{
struct dma_client *client;
client = kzalloc(sizeof(*client), GFP_KERNEL);
if (!client)
return NULL;
INIT_LIST_HEAD(&client->channels);
spin_lock_init(&client->lock);
client->chans_desired = 0;
client->chan_count = 0;
client->event_callback = event_callback;
mutex_lock(&dma_list_mutex);
list_add_tail(&client->global_node, &dma_client_list);
mutex_unlock(&dma_list_mutex);
return client;
}
/**
* dma_async_client_unregister - unregister a client and free the &dma_client
* @client:
*
* Force frees any allocated DMA channels, frees the &dma_client memory
*/
void dma_async_client_unregister(struct dma_client *client)
{
struct dma_chan *chan;
if (!client)
return;
rcu_read_lock();
list_for_each_entry_rcu(chan, &client->channels, client_node)
dma_client_chan_free(chan);
rcu_read_unlock();
mutex_lock(&dma_list_mutex);
list_del(&client->global_node);
mutex_unlock(&dma_list_mutex);
kfree(client);
dma_chans_rebalance();
}
/**
* dma_async_client_chan_request - request DMA channels
* @client: &dma_client
* @number: count of DMA channels requested
*
* Clients call dma_async_client_chan_request() to specify how many
* DMA channels they need, 0 to free all currently allocated.
* The resulting allocations/frees are indicated to the client via the
* event callback.
*/
void dma_async_client_chan_request(struct dma_client *client,
unsigned int number)
{
client->chans_desired = number;
dma_chans_rebalance();
}
/**
* dma_async_device_register -
* @device: &dma_device
*/
int dma_async_device_register(struct dma_device *device)
{
static int id;
int chancnt = 0;
struct dma_chan* chan;
if (!device)
return -ENODEV;
init_completion(&device->done);
kref_init(&device->refcount);
device->dev_id = id++;
/* represent channels in sysfs. Probably want devs too */
list_for_each_entry(chan, &device->channels, device_node) {
chan->local = alloc_percpu(typeof(*chan->local));
if (chan->local == NULL)
continue;
chan->chan_id = chancnt++;
chan->class_dev.class = &dma_devclass;
chan->class_dev.dev = NULL;
snprintf(chan->class_dev.class_id, BUS_ID_SIZE, "dma%dchan%d",
device->dev_id, chan->chan_id);
kref_get(&device->refcount);
class_device_register(&chan->class_dev);
}
mutex_lock(&dma_list_mutex);
list_add_tail(&device->global_node, &dma_device_list);
mutex_unlock(&dma_list_mutex);
dma_chans_rebalance();
return 0;
}
/**
* dma_async_device_unregister -
* @device: &dma_device
*/
static void dma_async_device_cleanup(struct kref *kref)
{
struct dma_device *device;
device = container_of(kref, struct dma_device, refcount);
complete(&device->done);
}
void dma_async_device_unregister(struct dma_device* device)
{
struct dma_chan *chan;
unsigned long flags;
mutex_lock(&dma_list_mutex);
list_del(&device->global_node);
mutex_unlock(&dma_list_mutex);
list_for_each_entry(chan, &device->channels, device_node) {
if (chan->client) {
spin_lock_irqsave(&chan->client->lock, flags);
list_del(&chan->client_node);
chan->client->chan_count--;
spin_unlock_irqrestore(&chan->client->lock, flags);
chan->client->event_callback(chan->client,
chan,
DMA_RESOURCE_REMOVED);
dma_client_chan_free(chan);
}
class_device_unregister(&chan->class_dev);
}
dma_chans_rebalance();
kref_put(&device->refcount, dma_async_device_cleanup);
wait_for_completion(&device->done);
}
static int __init dma_bus_init(void)
{
mutex_init(&dma_list_mutex);
return class_register(&dma_devclass);
}
subsys_initcall(dma_bus_init);
EXPORT_SYMBOL(dma_async_client_register);
EXPORT_SYMBOL(dma_async_client_unregister);
EXPORT_SYMBOL(dma_async_client_chan_request);
EXPORT_SYMBOL(dma_async_memcpy_buf_to_buf);
EXPORT_SYMBOL(dma_async_memcpy_buf_to_pg);
EXPORT_SYMBOL(dma_async_memcpy_pg_to_pg);
EXPORT_SYMBOL(dma_async_memcpy_complete);
EXPORT_SYMBOL(dma_async_memcpy_issue_pending);
EXPORT_SYMBOL(dma_async_device_register);
EXPORT_SYMBOL(dma_async_device_unregister);
EXPORT_SYMBOL(dma_chan_cleanup);