diff options
Diffstat (limited to 'drivers/dma/dmaengine.c')
| -rw-r--r-- | drivers/dma/dmaengine.c | 408 |
1 files changed, 408 insertions, 0 deletions
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c new file mode 100644 index 00000000000..5829143558e --- /dev/null +++ b/drivers/dma/dmaengine.c @@ -0,0 +1,408 @@ +/* + * 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_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 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_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 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_possible_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); |