ACPI: thinkpad-acpi: improve dock subdriver initialization
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / drivers / dma / dmaengine.c
blob15278044295cbf38559c7a5d0410f3aa1873b29e
1 /*
2 * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
4 * This program is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License as published by the Free
6 * Software Foundation; either version 2 of the License, or (at your option)
7 * any later version.
9 * This program is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
12 * more details.
14 * You should have received a copy of the GNU General Public License along with
15 * this program; if not, write to the Free Software Foundation, Inc., 59
16 * Temple Place - Suite 330, Boston, MA 02111-1307, USA.
18 * The full GNU General Public License is included in this distribution in the
19 * file called COPYING.
23 * This code implements the DMA subsystem. It provides a HW-neutral interface
24 * for other kernel code to use asynchronous memory copy capabilities,
25 * if present, and allows different HW DMA drivers to register as providing
26 * this capability.
28 * Due to the fact we are accelerating what is already a relatively fast
29 * operation, the code goes to great lengths to avoid additional overhead,
30 * such as locking.
32 * LOCKING:
34 * The subsystem keeps two global lists, dma_device_list and dma_client_list.
35 * Both of these are protected by a mutex, dma_list_mutex.
37 * Each device has a channels list, which runs unlocked but is never modified
38 * once the device is registered, it's just setup by the driver.
40 * Each client has a channels list, it's only modified under the client->lock
41 * and in an RCU callback, so it's safe to read under rcu_read_lock().
43 * Each device has a kref, which is initialized to 1 when the device is
44 * registered. A kref_put is done for each class_device registered. When the
45 * class_device is released, the coresponding kref_put is done in the release
46 * method. Every time one of the device's channels is allocated to a client,
47 * a kref_get occurs. When the channel is freed, the coresponding kref_put
48 * happens. The device's release function does a completion, so
49 * unregister_device does a remove event, class_device_unregister, a kref_put
50 * for the first reference, then waits on the completion for all other
51 * references to finish.
53 * Each channel has an open-coded implementation of Rusty Russell's "bigref,"
54 * with a kref and a per_cpu local_t. A single reference is set when on an
55 * ADDED event, and removed with a REMOVE event. Net DMA client takes an
56 * extra reference per outstanding transaction. The relase function does a
57 * kref_put on the device. -ChrisL
60 #include <linux/init.h>
61 #include <linux/module.h>
62 #include <linux/device.h>
63 #include <linux/dmaengine.h>
64 #include <linux/hardirq.h>
65 #include <linux/spinlock.h>
66 #include <linux/percpu.h>
67 #include <linux/rcupdate.h>
68 #include <linux/mutex.h>
70 static DEFINE_MUTEX(dma_list_mutex);
71 static LIST_HEAD(dma_device_list);
72 static LIST_HEAD(dma_client_list);
74 /* --- sysfs implementation --- */
76 static ssize_t show_memcpy_count(struct class_device *cd, char *buf)
78 struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
79 unsigned long count = 0;
80 int i;
82 for_each_possible_cpu(i)
83 count += per_cpu_ptr(chan->local, i)->memcpy_count;
85 return sprintf(buf, "%lu\n", count);
88 static ssize_t show_bytes_transferred(struct class_device *cd, char *buf)
90 struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
91 unsigned long count = 0;
92 int i;
94 for_each_possible_cpu(i)
95 count += per_cpu_ptr(chan->local, i)->bytes_transferred;
97 return sprintf(buf, "%lu\n", count);
100 static ssize_t show_in_use(struct class_device *cd, char *buf)
102 struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
104 return sprintf(buf, "%d\n", (chan->client ? 1 : 0));
107 static struct class_device_attribute dma_class_attrs[] = {
108 __ATTR(memcpy_count, S_IRUGO, show_memcpy_count, NULL),
109 __ATTR(bytes_transferred, S_IRUGO, show_bytes_transferred, NULL),
110 __ATTR(in_use, S_IRUGO, show_in_use, NULL),
111 __ATTR_NULL
114 static void dma_async_device_cleanup(struct kref *kref);
116 static void dma_class_dev_release(struct class_device *cd)
118 struct dma_chan *chan = container_of(cd, struct dma_chan, class_dev);
119 kref_put(&chan->device->refcount, dma_async_device_cleanup);
122 static struct class dma_devclass = {
123 .name = "dma",
124 .class_dev_attrs = dma_class_attrs,
125 .release = dma_class_dev_release,
128 /* --- client and device registration --- */
131 * dma_client_chan_alloc - try to allocate a channel to a client
132 * @client: &dma_client
134 * Called with dma_list_mutex held.
136 static struct dma_chan *dma_client_chan_alloc(struct dma_client *client)
138 struct dma_device *device;
139 struct dma_chan *chan;
140 unsigned long flags;
141 int desc; /* allocated descriptor count */
143 /* Find a channel, any DMA engine will do */
144 list_for_each_entry(device, &dma_device_list, global_node) {
145 list_for_each_entry(chan, &device->channels, device_node) {
146 if (chan->client)
147 continue;
149 desc = chan->device->device_alloc_chan_resources(chan);
150 if (desc >= 0) {
151 kref_get(&device->refcount);
152 kref_init(&chan->refcount);
153 chan->slow_ref = 0;
154 INIT_RCU_HEAD(&chan->rcu);
155 chan->client = client;
156 spin_lock_irqsave(&client->lock, flags);
157 list_add_tail_rcu(&chan->client_node,
158 &client->channels);
159 spin_unlock_irqrestore(&client->lock, flags);
160 return chan;
165 return NULL;
169 * dma_chan_cleanup - release a DMA channel's resources
170 * @kref: kernel reference structure that contains the DMA channel device
172 void dma_chan_cleanup(struct kref *kref)
174 struct dma_chan *chan = container_of(kref, struct dma_chan, refcount);
175 chan->device->device_free_chan_resources(chan);
176 chan->client = NULL;
177 kref_put(&chan->device->refcount, dma_async_device_cleanup);
180 static void dma_chan_free_rcu(struct rcu_head *rcu)
182 struct dma_chan *chan = container_of(rcu, struct dma_chan, rcu);
183 int bias = 0x7FFFFFFF;
184 int i;
185 for_each_possible_cpu(i)
186 bias -= local_read(&per_cpu_ptr(chan->local, i)->refcount);
187 atomic_sub(bias, &chan->refcount.refcount);
188 kref_put(&chan->refcount, dma_chan_cleanup);
191 static void dma_client_chan_free(struct dma_chan *chan)
193 atomic_add(0x7FFFFFFF, &chan->refcount.refcount);
194 chan->slow_ref = 1;
195 call_rcu(&chan->rcu, dma_chan_free_rcu);
199 * dma_chans_rebalance - reallocate channels to clients
201 * When the number of DMA channel in the system changes,
202 * channels need to be rebalanced among clients.
204 static void dma_chans_rebalance(void)
206 struct dma_client *client;
207 struct dma_chan *chan;
208 unsigned long flags;
210 mutex_lock(&dma_list_mutex);
212 list_for_each_entry(client, &dma_client_list, global_node) {
213 while (client->chans_desired > client->chan_count) {
214 chan = dma_client_chan_alloc(client);
215 if (!chan)
216 break;
217 client->chan_count++;
218 client->event_callback(client,
219 chan,
220 DMA_RESOURCE_ADDED);
222 while (client->chans_desired < client->chan_count) {
223 spin_lock_irqsave(&client->lock, flags);
224 chan = list_entry(client->channels.next,
225 struct dma_chan,
226 client_node);
227 list_del_rcu(&chan->client_node);
228 spin_unlock_irqrestore(&client->lock, flags);
229 client->chan_count--;
230 client->event_callback(client,
231 chan,
232 DMA_RESOURCE_REMOVED);
233 dma_client_chan_free(chan);
237 mutex_unlock(&dma_list_mutex);
241 * dma_async_client_register - allocate and register a &dma_client
242 * @event_callback: callback for notification of channel addition/removal
244 struct dma_client *dma_async_client_register(dma_event_callback event_callback)
246 struct dma_client *client;
248 client = kzalloc(sizeof(*client), GFP_KERNEL);
249 if (!client)
250 return NULL;
252 INIT_LIST_HEAD(&client->channels);
253 spin_lock_init(&client->lock);
254 client->chans_desired = 0;
255 client->chan_count = 0;
256 client->event_callback = event_callback;
258 mutex_lock(&dma_list_mutex);
259 list_add_tail(&client->global_node, &dma_client_list);
260 mutex_unlock(&dma_list_mutex);
262 return client;
266 * dma_async_client_unregister - unregister a client and free the &dma_client
267 * @client: &dma_client to free
269 * Force frees any allocated DMA channels, frees the &dma_client memory
271 void dma_async_client_unregister(struct dma_client *client)
273 struct dma_chan *chan;
275 if (!client)
276 return;
278 rcu_read_lock();
279 list_for_each_entry_rcu(chan, &client->channels, client_node)
280 dma_client_chan_free(chan);
281 rcu_read_unlock();
283 mutex_lock(&dma_list_mutex);
284 list_del(&client->global_node);
285 mutex_unlock(&dma_list_mutex);
287 kfree(client);
288 dma_chans_rebalance();
292 * dma_async_client_chan_request - request DMA channels
293 * @client: &dma_client
294 * @number: count of DMA channels requested
296 * Clients call dma_async_client_chan_request() to specify how many
297 * DMA channels they need, 0 to free all currently allocated.
298 * The resulting allocations/frees are indicated to the client via the
299 * event callback.
301 void dma_async_client_chan_request(struct dma_client *client,
302 unsigned int number)
304 client->chans_desired = number;
305 dma_chans_rebalance();
309 * dma_async_device_register - registers DMA devices found
310 * @device: &dma_device
312 int dma_async_device_register(struct dma_device *device)
314 static int id;
315 int chancnt = 0;
316 struct dma_chan* chan;
318 if (!device)
319 return -ENODEV;
321 init_completion(&device->done);
322 kref_init(&device->refcount);
323 device->dev_id = id++;
325 /* represent channels in sysfs. Probably want devs too */
326 list_for_each_entry(chan, &device->channels, device_node) {
327 chan->local = alloc_percpu(typeof(*chan->local));
328 if (chan->local == NULL)
329 continue;
331 chan->chan_id = chancnt++;
332 chan->class_dev.class = &dma_devclass;
333 chan->class_dev.dev = NULL;
334 snprintf(chan->class_dev.class_id, BUS_ID_SIZE, "dma%dchan%d",
335 device->dev_id, chan->chan_id);
337 kref_get(&device->refcount);
338 class_device_register(&chan->class_dev);
341 mutex_lock(&dma_list_mutex);
342 list_add_tail(&device->global_node, &dma_device_list);
343 mutex_unlock(&dma_list_mutex);
345 dma_chans_rebalance();
347 return 0;
351 * dma_async_device_cleanup - function called when all references are released
352 * @kref: kernel reference object
354 static void dma_async_device_cleanup(struct kref *kref)
356 struct dma_device *device;
358 device = container_of(kref, struct dma_device, refcount);
359 complete(&device->done);
363 * dma_async_device_unregister - unregisters DMA devices
364 * @device: &dma_device
366 void dma_async_device_unregister(struct dma_device *device)
368 struct dma_chan *chan;
369 unsigned long flags;
371 mutex_lock(&dma_list_mutex);
372 list_del(&device->global_node);
373 mutex_unlock(&dma_list_mutex);
375 list_for_each_entry(chan, &device->channels, device_node) {
376 if (chan->client) {
377 spin_lock_irqsave(&chan->client->lock, flags);
378 list_del(&chan->client_node);
379 chan->client->chan_count--;
380 spin_unlock_irqrestore(&chan->client->lock, flags);
381 chan->client->event_callback(chan->client,
382 chan,
383 DMA_RESOURCE_REMOVED);
384 dma_client_chan_free(chan);
386 class_device_unregister(&chan->class_dev);
388 dma_chans_rebalance();
390 kref_put(&device->refcount, dma_async_device_cleanup);
391 wait_for_completion(&device->done);
394 static int __init dma_bus_init(void)
396 mutex_init(&dma_list_mutex);
397 return class_register(&dma_devclass);
400 subsys_initcall(dma_bus_init);
402 EXPORT_SYMBOL(dma_async_client_register);
403 EXPORT_SYMBOL(dma_async_client_unregister);
404 EXPORT_SYMBOL(dma_async_client_chan_request);
405 EXPORT_SYMBOL(dma_async_memcpy_buf_to_buf);
406 EXPORT_SYMBOL(dma_async_memcpy_buf_to_pg);
407 EXPORT_SYMBOL(dma_async_memcpy_pg_to_pg);
408 EXPORT_SYMBOL(dma_async_memcpy_complete);
409 EXPORT_SYMBOL(dma_async_memcpy_issue_pending);
410 EXPORT_SYMBOL(dma_async_device_register);
411 EXPORT_SYMBOL(dma_async_device_unregister);
412 EXPORT_SYMBOL(dma_chan_cleanup);