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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 is responsible for keeping track of the channels it uses. See
* the definition of dma_event_callback in dmaengine.h.
*
* Each device has a kref, which is initialized to 1 when the device is
* registered. A kref_get is done for each device registered. When the
* device is released, the corresponding 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 corresponding kref_put
* happens. The device's release function does a completion, so
* unregister_device does a remove event, 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 dma_chan_get is called when a client
* signals that it wants to use a channel, and dma_chan_put is called when
* a channel is removed or a client using it is unregistered. A client can
* take extra references per outstanding transaction, as is the case with
* the NET DMA client. The release function does a kref_put on the device.
* -ChrisL, DanW
*/
#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>
static DEFINE_MUTEX(dma_list_mutex);
static LIST_HEAD(dma_device_list);
static LIST_HEAD(dma_client_list);
static long dmaengine_ref_count;
/* --- sysfs implementation --- */
static ssize_t show_memcpy_count(struct device *dev, struct device_attribute *attr, char *buf)
{
struct dma_chan *chan = to_dma_chan(dev);
unsigned long count = 0;
int i;
for_each_possible_cpu(i)
count += per_cpu_ptr(chan->local, i)->memcpy_count;
return sprintf(buf, "%lu\n", count);
}
static ssize_t show_bytes_transferred(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct dma_chan *chan = to_dma_chan(dev);
unsigned long count = 0;
int i;
for_each_possible_cpu(i)
count += per_cpu_ptr(chan->local, i)->bytes_transferred;
return sprintf(buf, "%lu\n", count);
}
static ssize_t show_in_use(struct device *dev, struct device_attribute *attr, char *buf)
{
struct dma_chan *chan = to_dma_chan(dev);
return sprintf(buf, "%d\n", chan->client_count);
}
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 dma_async_device_cleanup(struct kref *kref);
static void dma_dev_release(struct device *dev)
{
struct dma_chan *chan = to_dma_chan(dev);
kref_put(&chan->device->refcount, dma_async_device_cleanup);
}
static struct class dma_devclass = {
.name = "dma",
.dev_attrs = dma_attrs,
.dev_release = dma_dev_release,
};
/* --- client and device registration --- */
#define dma_chan_satisfies_mask(chan, mask) \
__dma_chan_satisfies_mask((chan), &(mask))
static int
__dma_chan_satisfies_mask(struct dma_chan *chan, dma_cap_mask_t *want)
{
dma_cap_mask_t has;
bitmap_and(has.bits, want->bits, chan->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, NULL);
if (desc_cnt < 0) {
err = desc_cnt;
chan->client_count = 0;
module_put(owner);
} else
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);
}
/**
* dma_client_chan_alloc - try to allocate channels to a client
* @client: &dma_client
*
* Called with dma_list_mutex held.
*/
static void dma_client_chan_alloc(struct dma_client *client)
{
struct dma_device *device;
struct dma_chan *chan;
enum dma_state_client ack;
/* Find a channel */
list_for_each_entry(device, &dma_device_list, global_node) {
/* Does the client require a specific DMA controller? */
if (client->slave &&
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