1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * core routines for the asynchronous memory transfer/transform api
4 *
5 * Copyright © 2006, Intel Corporation.
6 *
7 * Dan Williams <dan.j.williams@intel.com>
8 *
9 * with architecture considerations by:
10 * Neil Brown <neilb@suse.de>
11 * Jeff Garzik <jeff@garzik.org>
12 */
13 #include <linux/rculist.h>
14 #include <linux/module.h>
15 #include <linux/kernel.h>
16 #include <linux/async_tx.h>
17
18 #ifdef CONFIG_DMA_ENGINE
19 static int __init async_tx_init(void)
20 {
21 async_dmaengine_get();
22
23 printk(KERN_INFO "async_tx: api initialized (async)\n");
24
25 return 0;
26 }
27
28 static void __exit async_tx_exit(void)
29 {
30 async_dmaengine_put();
31 }
32
33 module_init(async_tx_init);
34 module_exit(async_tx_exit);
35
36 /**
37 * __async_tx_find_channel - find a channel to carry out the operation or let
38 * the transaction execute synchronously
39 * @submit: transaction dependency and submission modifiers
40 * @tx_type: transaction type
41 */
42 struct dma_chan *
43 __async_tx_find_channel(struct async_submit_ctl *submit,
44 enum dma_transaction_type tx_type)
45 {
46 struct dma_async_tx_descriptor *depend_tx = submit->depend_tx;
47
48 /* see if we can keep the chain on one channel */
49 if (depend_tx &&
50 dma_has_cap(tx_type, depend_tx->chan->device->cap_mask))
51 return depend_tx->chan;
52 return async_dma_find_channel(tx_type);
53 }
54 EXPORT_SYMBOL_GPL(__async_tx_find_channel);
55 #endif
56
57
58 /**
59 * async_tx_channel_switch - queue an interrupt descriptor with a dependency
60 * pre-attached.
61 * @depend_tx: the operation that must finish before the new operation runs
62 * @tx: the new operation
63 */
64 static void
65 async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
66 struct dma_async_tx_descriptor *tx)
67 {
68 struct dma_chan *chan = depend_tx->chan;
69 struct dma_device *device = chan->device;
70 struct dma_async_tx_descriptor *intr_tx = (void *) ~0;
71
72 /* first check to see if we can still append to depend_tx */
73 txd_lock(depend_tx);
74 if (txd_parent(depend_tx) && depend_tx->chan == tx->chan) {
75 txd_chain(depend_tx, tx);
76 intr_tx = NULL;
77 }
78 txd_unlock(depend_tx);
79
80 /* attached dependency, flush the parent channel */
81 if (!intr_tx) {
82 device->device_issue_pending(chan);
83 return;
84 }
85
86 /* see if we can schedule an interrupt
87 * otherwise poll for completion
88 */
89 if (dma_has_cap(DMA_INTERRUPT, device->cap_mask))
90 intr_tx = device->device_prep_dma_interrupt(chan, 0);
91 else
92 intr_tx = NULL;
93
94 if (intr_tx) {
95 intr_tx->callback = NULL;
96 intr_tx->callback_param = NULL;
97 /* safe to chain outside the lock since we know we are
98 * not submitted yet
99 */
100 txd_chain(intr_tx, tx);
101
102 /* check if we need to append */
103 txd_lock(depend_tx);
104 if (txd_parent(depend_tx)) {
105 txd_chain(depend_tx, intr_tx);
106 async_tx_ack(intr_tx);
107 intr_tx = NULL;
108 }
109 txd_unlock(depend_tx);
110
111 if (intr_tx) {
112 txd_clear_parent(intr_tx);
113 intr_tx->tx_submit(intr_tx);
114 async_tx_ack(intr_tx);
115 }
116 device->device_issue_pending(chan);
117 } else {
118 if (dma_wait_for_async_tx(depend_tx) != DMA_COMPLETE)
119 panic("%s: DMA error waiting for depend_tx\n",
120 __func__);
121 tx->tx_submit(tx);
122 }
123 }
124
125
126 /**
127 * submit_disposition - flags for routing an incoming operation
128 * @ASYNC_TX_SUBMITTED: we were able to append the new operation under the lock
129 * @ASYNC_TX_CHANNEL_SWITCH: when the lock is dropped schedule a channel switch
130 * @ASYNC_TX_DIRECT_SUBMIT: when the lock is dropped submit directly
131 *
132 * while holding depend_tx->lock we must avoid submitting new operations
133 * to prevent a circular locking dependency with drivers that already
134 * hold a channel lock when calling async_tx_run_dependencies.
135 */
136 enum submit_disposition {
137 ASYNC_TX_SUBMITTED,
138 ASYNC_TX_CHANNEL_SWITCH,
139 ASYNC_TX_DIRECT_SUBMIT,
140 };
141
142 void
143 async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
144 struct async_submit_ctl *submit)
145 {
146 struct dma_async_tx_descriptor *depend_tx = submit->depend_tx;
147
148 tx->callback = submit->cb_fn;
149 tx->callback_param = submit->cb_param;
150
151 if (depend_tx) {
152 enum submit_disposition s;
153
154 /* sanity check the dependency chain:
155 * 1/ if ack is already set then we cannot be sure
156 * we are referring to the correct operation
157 * 2/ dependencies are 1:1 i.e. two transactions can
158 * not depend on the same parent
159 */
160 BUG_ON(async_tx_test_ack(depend_tx) || txd_next(depend_tx) ||
161 txd_parent(tx));
162
163 /* the lock prevents async_tx_run_dependencies from missing
164 * the setting of ->next when ->parent != NULL
165 */
166 txd_lock(depend_tx);
167 if (txd_parent(depend_tx)) {
168 /* we have a parent so we can not submit directly
169 * if we are staying on the same channel: append
170 * else: channel switch
171 */
172 if (depend_tx->chan == chan) {
173 txd_chain(depend_tx, tx);
174 s = ASYNC_TX_SUBMITTED;
175 } else
176 s = ASYNC_TX_CHANNEL_SWITCH;
177 } else {
178 /* we do not have a parent so we may be able to submit
179 * directly if we are staying on the same channel
180 */
181 if (depend_tx->chan == chan)
182 s = ASYNC_TX_DIRECT_SUBMIT;
183 else
184 s = ASYNC_TX_CHANNEL_SWITCH;
185 }
186 txd_unlock(depend_tx);
187
188 switch (s) {
189 case ASYNC_TX_SUBMITTED:
190 break;
191 case ASYNC_TX_CHANNEL_SWITCH:
192 async_tx_channel_switch(depend_tx, tx);
193 break;
194 case ASYNC_TX_DIRECT_SUBMIT:
195 txd_clear_parent(tx);
196 tx->tx_submit(tx);
197 break;
198 }
199 } else {
200 txd_clear_parent(tx);
201 tx->tx_submit(tx);
202 }
203
204 if (submit->flags & ASYNC_TX_ACK)
205 async_tx_ack(tx);
206
207 if (depend_tx)
208 async_tx_ack(depend_tx);
209 }
210 EXPORT_SYMBOL_GPL(async_tx_submit);
211
212 /**
213 * async_trigger_callback - schedules the callback function to be run
214 * @submit: submission and completion parameters
215 *
216 * honored flags: ASYNC_TX_ACK
217 *
218 * The callback is run after any dependent operations have completed.
219 */
220 struct dma_async_tx_descriptor *
221 async_trigger_callback(struct async_submit_ctl *submit)
222 {
223 struct dma_chan *chan;
224 struct dma_device *device;
225 struct dma_async_tx_descriptor *tx;
226 struct dma_async_tx_descriptor *depend_tx = submit->depend_tx;
227
228 if (depend_tx) {
229 chan = depend_tx->chan;
230 device = chan->device;
231
232 /* see if we can schedule an interrupt
233 * otherwise poll for completion
234 */
235 if (device && !dma_has_cap(DMA_INTERRUPT, device->cap_mask))
236 device = NULL;
237
238 tx = device ? device->device_prep_dma_interrupt(chan, 0) : NULL;
239 } else
240 tx = NULL;
241
242 if (tx) {
243 pr_debug("%s: (async)\n", __func__);
244
245 async_tx_submit(chan, tx, submit);
246 } else {
247 pr_debug("%s: (sync)\n", __func__);
248
249 /* wait for any prerequisite operations */
250 async_tx_quiesce(&submit->depend_tx);
251
252 async_tx_sync_epilog(submit);
253 }
254
255 return tx;
256 }
257 EXPORT_SYMBOL_GPL(async_trigger_callback);
258
259 /**
260 * async_tx_quiesce - ensure tx is complete and freeable upon return
261 * @tx - transaction to quiesce
262 */
263 void async_tx_quiesce(struct dma_async_tx_descriptor **tx)
264 {
265 if (*tx) {
266 /* if ack is already set then we cannot be sure
267 * we are referring to the correct operation
268 */
269 BUG_ON(async_tx_test_ack(*tx));
270 if (dma_wait_for_async_tx(*tx) != DMA_COMPLETE)
271 panic("%s: DMA error waiting for transaction\n",
272 __func__);
273 async_tx_ack(*tx);
274 *tx = NULL;
275 }
276 }
277 EXPORT_SYMBOL_GPL(async_tx_quiesce);
278
279 MODULE_AUTHOR("Intel Corporation");
280 MODULE_DESCRIPTION("Asynchronous Bulk Memory Transactions API");
281 MODULE_LICENSE("GPL");