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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Mailbox: Common code for Mailbox controllers and users
4 *
5 * Copyright (C) 2013-2014 Linaro Ltd.
6 * Author: Jassi Brar <[email protected]>
7 */
8
9#include <linux/cleanup.h>
10#include <linux/debugfs.h>
11#include <linux/delay.h>
12#include <linux/device.h>
13#include <linux/err.h>
14#include <linux/mailbox_client.h>
15#include <linux/mailbox_controller.h>
16#include <linux/module.h>
17#include <linux/mutex.h>
18#include <linux/of.h>
19#include <linux/property.h>
20#include <linux/seq_file.h>
21#include <linux/spinlock.h>
22
23static LIST_HEAD(mbox_cons);
24static DEFINE_MUTEX(con_mutex);
25
26static int add_to_rbuf(struct mbox_chan *chan, void *mssg)
27{
28 int idx;
29
30 guard(spinlock_irqsave)(&chan->lock);
31
32 /* See if there is any space left */
33 if (chan->msg_count == MBOX_TX_QUEUE_LEN)
34 return -ENOBUFS;
35
36 idx = chan->msg_free;
37 chan->msg_data[idx] = mssg;
38 chan->msg_count++;
39
40 if (idx == MBOX_TX_QUEUE_LEN - 1)
41 chan->msg_free = 0;
42 else
43 chan->msg_free++;
44
45 return idx;
46}
47
48static void msg_submit(struct mbox_chan *chan)
49{
50 unsigned count, idx;
51 void *data;
52 int err = -EBUSY;
53
54 scoped_guard(spinlock_irqsave, &chan->lock) {
55 if (!chan->msg_count || chan->active_req != MBOX_NO_MSG)
56 break;
57
58 count = chan->msg_count;
59 idx = chan->msg_free;
60 if (idx >= count)
61 idx -= count;
62 else
63 idx += MBOX_TX_QUEUE_LEN - count;
64
65 data = chan->msg_data[idx];
66
67 if (chan->cl->tx_prepare)
68 chan->cl->tx_prepare(chan->cl, data);
69 /* Try to submit a message to the MBOX controller */
70 err = chan->mbox->ops->send_data(chan, data);
71 if (!err) {
72 chan->active_req = data;
73 chan->msg_count--;
74 }
75 }
76
77 if (!err && (chan->txdone_method & MBOX_TXDONE_BY_POLL)) {
78 /* kick start the timer immediately to avoid delays */
79 scoped_guard(spinlock_irqsave, &chan->mbox->poll_hrt_lock)
80 hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL);
81 }
82}
83
84static void tx_tick(struct mbox_chan *chan, int r)
85{
86 void *mssg;
87
88 scoped_guard(spinlock_irqsave, &chan->lock) {
89 mssg = chan->active_req;
90 chan->active_req = MBOX_NO_MSG;
91 }
92
93 /* Submit next message */
94 msg_submit(chan);
95
96 if (mssg == MBOX_NO_MSG)
97 return;
98
99 /* Notify the client */
100 if (chan->cl->tx_done)
101 chan->cl->tx_done(chan->cl, mssg, r);
102
103 if (r != -ETIME && chan->cl->tx_block) {
104 chan->tx_status = r;
105 complete(&chan->tx_complete);
106 }
107}
108
109static enum hrtimer_restart txdone_hrtimer(struct hrtimer *hrtimer)
110{
111 struct mbox_controller *mbox =
112 container_of(hrtimer, struct mbox_controller, poll_hrt);
113 bool txdone, resched = false;
114 int i;
115
116 for (i = 0; i < mbox->num_chans; i++) {
117 struct mbox_chan *chan = &mbox->chans[i];
118
119 if (chan->active_req != MBOX_NO_MSG && chan->cl) {
120 txdone = chan->mbox->ops->last_tx_done(chan);
121 if (txdone)
122 tx_tick(chan, 0);
123 else
124 resched = true;
125 }
126 }
127
128 if (resched) {
129 scoped_guard(spinlock_irqsave, &mbox->poll_hrt_lock) {
130 if (!hrtimer_is_queued(hrtimer))
131 hrtimer_forward_now(hrtimer, ms_to_ktime(mbox->txpoll_period));
132 }
133
134 return HRTIMER_RESTART;
135 }
136 return HRTIMER_NORESTART;
137}
138
139/**
140 * mbox_chan_received_data - A way for controller driver to push data
141 * received from remote to the upper layer.
142 * @chan: Pointer to the mailbox channel on which RX happened.
143 * @mssg: Client specific message typecasted as void *
144 *
145 * After startup and before shutdown any data received on the chan
146 * is passed on to the API via atomic mbox_chan_received_data().
147 * The controller should ACK the RX only after this call returns.
148 */
149void mbox_chan_received_data(struct mbox_chan *chan, void *mssg)
150{
151 /* No buffering the received data */
152 if (chan->cl->rx_callback)
153 chan->cl->rx_callback(chan->cl, mssg);
154}
155EXPORT_SYMBOL_GPL(mbox_chan_received_data);
156
157/**
158 * mbox_chan_txdone - A way for controller driver to notify the
159 * framework that the last TX has completed.
160 * @chan: Pointer to the mailbox chan on which TX happened.
161 * @r: Status of last TX - OK or ERROR
162 *
163 * The controller that has IRQ for TX ACK calls this atomic API
164 * to tick the TX state machine. It works only if txdone_irq
165 * is set by the controller.
166 */
167void mbox_chan_txdone(struct mbox_chan *chan, int r)
168{
169 if (unlikely(!(chan->txdone_method & MBOX_TXDONE_BY_IRQ))) {
170 dev_err(chan->mbox->dev,
171 "Controller can't run the TX ticker\n");
172 return;
173 }
174
175 tx_tick(chan, r);
176}
177EXPORT_SYMBOL_GPL(mbox_chan_txdone);
178
179/**
180 * mbox_client_txdone - The way for a client to run the TX state machine.
181 * @chan: Mailbox channel assigned to this client.
182 * @r: Success status of last transmission.
183 *
184 * The client/protocol had received some 'ACK' packet and it notifies
185 * the API that the last packet was sent successfully. This only works
186 * if the controller can't sense TX-Done.
187 */
188void mbox_client_txdone(struct mbox_chan *chan, int r)
189{
190 if (unlikely(!(chan->txdone_method & MBOX_TXDONE_BY_ACK))) {
191 dev_err(chan->mbox->dev, "Client can't run the TX ticker\n");
192 return;
193 }
194
195 tx_tick(chan, r);
196}
197EXPORT_SYMBOL_GPL(mbox_client_txdone);
198
199/**
200 * mbox_client_peek_data - A way for client driver to pull data
201 * received from remote by the controller.
202 * @chan: Mailbox channel assigned to this client.
203 *
204 * A poke to controller driver for any received data.
205 * The data is actually passed onto client via the
206 * mbox_chan_received_data()
207 * The call can be made from atomic context, so the controller's
208 * implementation of peek_data() must not sleep.
209 *
210 * Return: True, if controller has, and is going to push after this,
211 * some data.
212 * False, if controller doesn't have any data to be read.
213 */
214bool mbox_client_peek_data(struct mbox_chan *chan)
215{
216 if (chan->mbox->ops->peek_data)
217 return chan->mbox->ops->peek_data(chan);
218
219 return false;
220}
221EXPORT_SYMBOL_GPL(mbox_client_peek_data);
222
223/**
224 * mbox_chan_tx_slots_available - Query the number of available TX queue slots.
225 * @chan: Mailbox channel to query.
226 *
227 * Clients may call this to check how many messages can be queued via
228 * mbox_send_message() before the channel's TX queue is full. This helps
229 * clients avoid the -ENOBUFS error without needing to increase
230 * MBOX_TX_QUEUE_LEN.
231 * This can be called from atomic context.
232 *
233 * Return: Number of available slots in the channel's TX queue.
234 */
235unsigned int mbox_chan_tx_slots_available(struct mbox_chan *chan)
236{
237 unsigned int ret;
238
239 guard(spinlock_irqsave)(&chan->lock);
240 ret = MBOX_TX_QUEUE_LEN - chan->msg_count;
241
242 return ret;
243}
244EXPORT_SYMBOL_GPL(mbox_chan_tx_slots_available);
245
246/**
247 * mbox_send_message - For client to submit a message to be
248 * sent to the remote.
249 * @chan: Mailbox channel assigned to this client.
250 * @mssg: Client specific message typecasted.
251 *
252 * For client to submit data to the controller destined for a remote
253 * processor. If the client had set 'tx_block', the call will return
254 * either when the remote receives the data or when 'tx_tout' millisecs
255 * run out.
256 * In non-blocking mode, the requests are buffered by the API and a
257 * non-negative token is returned for each queued request. If the request
258 * is not queued, a negative token is returned. Upon failure or successful
259 * TX, the API calls 'tx_done' from atomic context, from which the client
260 * could submit yet another request.
261 * The pointer to message should be preserved until it is sent
262 * over the chan, i.e, tx_done() is made.
263 * This function could be called from atomic context as it simply
264 * queues the data and returns a token against the request.
265 * In blocking mode, it is caller's responsibility to serialize threads'
266 * access to a channel if multi-threads are to send messages through the
267 * same channel, i.e. caller should not call this function until any
268 * previous call returns.
269 *
270 * Return: Non-negative integer for successful submission (non-blocking mode)
271 * or transmission over chan (blocking mode).
272 * Negative value denotes failure.
273 */
274int mbox_send_message(struct mbox_chan *chan, void *mssg)
275{
276 int t;
277
278 if (!chan || !chan->cl || mssg == MBOX_NO_MSG)
279 return -EINVAL;
280
281 t = add_to_rbuf(chan, mssg);
282 if (t < 0) {
283 dev_err(chan->mbox->dev, "Try increasing MBOX_TX_QUEUE_LEN\n");
284 return t;
285 }
286
287 msg_submit(chan);
288
289 if (chan->cl->tx_block) {
290 unsigned long wait;
291 int ret;
292
293 if (!chan->cl->tx_tout) /* wait forever */
294 wait = msecs_to_jiffies(3600000);
295 else
296 wait = msecs_to_jiffies(chan->cl->tx_tout);
297
298 ret = wait_for_completion_timeout(&chan->tx_complete, wait);
299 if (ret == 0) {
300 t = -ETIME;
301 tx_tick(chan, t);
302 } else if (chan->tx_status < 0) {
303 t = chan->tx_status;
304 }
305 }
306
307 return t;
308}
309EXPORT_SYMBOL_GPL(mbox_send_message);
310
311/**
312 * mbox_flush - flush a mailbox channel
313 * @chan: mailbox channel to flush
314 * @timeout: time, in milliseconds, to allow the flush operation to succeed
315 *
316 * Mailbox controllers that need to work in atomic context can implement the
317 * ->flush() callback to busy loop until a transmission has been completed.
318 * The implementation must call mbox_chan_txdone() upon success. Clients can
319 * call the mbox_flush() function at any time after mbox_send_message() to
320 * flush the transmission. After the function returns success, the mailbox
321 * transmission is guaranteed to have completed.
322 *
323 * Returns: 0 on success or a negative error code on failure.
324 */
325int mbox_flush(struct mbox_chan *chan, unsigned long timeout)
326{
327 int ret;
328
329 if (!chan->mbox->ops->flush)
330 return -ENOTSUPP;
331
332 ret = chan->mbox->ops->flush(chan, timeout);
333 if (ret < 0)
334 tx_tick(chan, ret);
335
336 return ret;
337}
338EXPORT_SYMBOL_GPL(mbox_flush);
339
340static void mbox_clean_and_put_channel(struct mbox_chan *chan)
341{
342 /* The queued TX requests are simply aborted, no callbacks are made */
343 scoped_guard(spinlock_irqsave, &chan->lock) {
344 chan->cl = NULL;
345 chan->active_req = MBOX_NO_MSG;
346 if (chan->txdone_method == MBOX_TXDONE_BY_ACK)
347 chan->txdone_method = MBOX_TXDONE_BY_POLL;
348 }
349
350 module_put(chan->mbox->dev->driver->owner);
351}
352
353static int __mbox_bind_client(struct mbox_chan *chan, struct mbox_client *cl)
354{
355 struct device *dev = cl->dev;
356 int ret;
357
358 if (chan->cl || !try_module_get(chan->mbox->dev->driver->owner)) {
359 dev_err(dev, "%s: mailbox not free\n", __func__);
360 return -EBUSY;
361 }
362
363 scoped_guard(spinlock_irqsave, &chan->lock) {
364 chan->msg_free = 0;
365 chan->msg_count = 0;
366 chan->active_req = MBOX_NO_MSG;
367 chan->cl = cl;
368 init_completion(&chan->tx_complete);
369
370 if (chan->txdone_method == MBOX_TXDONE_BY_POLL && cl->knows_txdone)
371 chan->txdone_method = MBOX_TXDONE_BY_ACK;
372 }
373
374 if (chan->mbox->ops->startup) {
375 ret = chan->mbox->ops->startup(chan);
376 if (ret) {
377 dev_err(dev, "Unable to startup the chan (%d)\n", ret);
378 mbox_clean_and_put_channel(chan);
379 return ret;
380 }
381 }
382
383 return 0;
384}
385
386/**
387 * mbox_bind_client - Bind client to a mailbox channel.
388 * @chan: The mailbox channel to bind the client to.
389 * @cl: Identity of the client requesting the channel.
390 *
391 * The Client specifies its requirements and capabilities while asking for
392 * a mailbox channel. It can't be called from atomic context.
393 * The channel is exclusively allocated and can't be used by another
394 * client before the owner calls mbox_free_channel.
395 * After assignment, any packet received on this channel will be
396 * handed over to the client via the 'rx_callback'.
397 * The framework holds reference to the client, so the mbox_client
398 * structure shouldn't be modified until the mbox_free_channel returns.
399 *
400 * Return: 0 if the channel was assigned to the client successfully.
401 * <0 for request failure.
402 */
403int mbox_bind_client(struct mbox_chan *chan, struct mbox_client *cl)
404{
405 guard(mutex)(&con_mutex);
406
407 return __mbox_bind_client(chan, cl);
408}
409EXPORT_SYMBOL_GPL(mbox_bind_client);
410
411/**
412 * mbox_request_channel - Request a mailbox channel.
413 * @cl: Identity of the client requesting the channel.
414 * @index: Index of mailbox specifier in 'mboxes' property.
415 *
416 * The Client specifies its requirements and capabilities while asking for
417 * a mailbox channel. It can't be called from atomic context.
418 * The channel is exclusively allocated and can't be used by another
419 * client before the owner calls mbox_free_channel.
420 * After assignment, any packet received on this channel will be
421 * handed over to the client via the 'rx_callback'.
422 * The framework holds reference to the client, so the mbox_client
423 * structure shouldn't be modified until the mbox_free_channel returns.
424 *
425 * Return: Pointer to the channel assigned to the client if successful.
426 * ERR_PTR for request failure.
427 */
428struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index)
429{
430 struct fwnode_reference_args fwspec;
431 struct fwnode_handle *fwnode;
432 struct mbox_controller *mbox;
433 struct of_phandle_args spec;
434 struct mbox_chan *chan;
435 struct device *dev;
436 unsigned int i;
437 int ret;
438
439 dev = cl->dev;
440 if (!dev) {
441 pr_debug("No owner device\n");
442 return ERR_PTR(-ENODEV);
443 }
444
445 fwnode = dev_fwnode(dev);
446 if (!fwnode) {
447 dev_dbg(dev, "No owner fwnode\n");
448 return ERR_PTR(-ENODEV);
449 }
450
451 ret = fwnode_property_get_reference_args(fwnode, "mboxes", "#mbox-cells",
452 0, index, &fwspec);
453 if (ret) {
454 dev_err(dev, "%s: can't parse \"%s\" property\n", __func__, "mboxes");
455 return ERR_PTR(ret);
456 }
457
458 spec.np = to_of_node(fwspec.fwnode);
459 spec.args_count = fwspec.nargs;
460 for (i = 0; i < spec.args_count; i++)
461 spec.args[i] = fwspec.args[i];
462
463 scoped_guard(mutex, &con_mutex) {
464 chan = ERR_PTR(-EPROBE_DEFER);
465 list_for_each_entry(mbox, &mbox_cons, node) {
466 if (device_match_fwnode(mbox->dev, fwspec.fwnode)) {
467 if (mbox->fw_xlate) {
468 chan = mbox->fw_xlate(mbox, &fwspec);
469 if (!IS_ERR(chan))
470 break;
471 } else if (mbox->of_xlate) {
472 chan = mbox->of_xlate(mbox, &spec);
473 if (!IS_ERR(chan))
474 break;
475 }
476 }
477 }
478
479 fwnode_handle_put(fwspec.fwnode);
480
481 if (IS_ERR(chan))
482 return chan;
483
484 ret = __mbox_bind_client(chan, cl);
485 if (ret)
486 chan = ERR_PTR(ret);
487 }
488
489 return chan;
490}
491EXPORT_SYMBOL_GPL(mbox_request_channel);
492
493struct mbox_chan *mbox_request_channel_byname(struct mbox_client *cl,
494 const char *name)
495{
496 int index = device_property_match_string(cl->dev, "mbox-names", name);
497
498 if (index < 0) {
499 dev_err(cl->dev, "%s() could not locate channel named \"%s\"\n",
500 __func__, name);
501 return ERR_PTR(index);
502 }
503 return mbox_request_channel(cl, index);
504}
505EXPORT_SYMBOL_GPL(mbox_request_channel_byname);
506
507/**
508 * mbox_free_channel - The client relinquishes control of a mailbox
509 * channel by this call.
510 * @chan: The mailbox channel to be freed.
511 */
512void mbox_free_channel(struct mbox_chan *chan)
513{
514 if (!chan || !chan->cl)
515 return;
516
517 if (chan->mbox->ops->shutdown)
518 chan->mbox->ops->shutdown(chan);
519
520 mbox_clean_and_put_channel(chan);
521}
522EXPORT_SYMBOL_GPL(mbox_free_channel);
523
524static struct mbox_chan *fw_mbox_index_xlate(struct mbox_controller *mbox,
525 const struct fwnode_reference_args *sp)
526{
527 if (sp->nargs < 1 || sp->args[0] >= mbox->num_chans)
528 return ERR_PTR(-EINVAL);
529
530 return &mbox->chans[sp->args[0]];
531}
532
533/**
534 * mbox_controller_register - Register the mailbox controller
535 * @mbox: Pointer to the mailbox controller.
536 *
537 * The controller driver registers its communication channels
538 */
539int mbox_controller_register(struct mbox_controller *mbox)
540{
541 int i, txdone;
542
543 if (!mbox || !mbox->dev || !mbox->ops || !mbox->chans || !mbox->num_chans)
544 return -EINVAL;
545
546 if (mbox->txdone_irq)
547 txdone = MBOX_TXDONE_BY_IRQ;
548 else if (mbox->txdone_poll)
549 txdone = MBOX_TXDONE_BY_POLL;
550 else /* It has to be ACK then */
551 txdone = MBOX_TXDONE_BY_ACK;
552
553 if (txdone == MBOX_TXDONE_BY_POLL) {
554
555 if (!mbox->ops->last_tx_done) {
556 dev_err(mbox->dev, "last_tx_done method is absent\n");
557 return -EINVAL;
558 }
559
560 hrtimer_setup(&mbox->poll_hrt, txdone_hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
561 spin_lock_init(&mbox->poll_hrt_lock);
562 }
563
564 for (i = 0; i < mbox->num_chans; i++) {
565 struct mbox_chan *chan = &mbox->chans[i];
566
567 chan->cl = NULL;
568 chan->mbox = mbox;
569 chan->active_req = MBOX_NO_MSG;
570 chan->txdone_method = txdone;
571 spin_lock_init(&chan->lock);
572 }
573
574 if (!mbox->fw_xlate && !mbox->of_xlate)
575 mbox->fw_xlate = fw_mbox_index_xlate;
576
577 scoped_guard(mutex, &con_mutex)
578 list_add_tail(&mbox->node, &mbox_cons);
579
580 return 0;
581}
582EXPORT_SYMBOL_GPL(mbox_controller_register);
583
584/**
585 * mbox_controller_unregister - Unregister the mailbox controller
586 * @mbox: Pointer to the mailbox controller.
587 */
588void mbox_controller_unregister(struct mbox_controller *mbox)
589{
590 int i;
591
592 if (!mbox)
593 return;
594
595 scoped_guard(mutex, &con_mutex) {
596 list_del(&mbox->node);
597
598 for (i = 0; i < mbox->num_chans; i++)
599 mbox_free_channel(&mbox->chans[i]);
600
601 if (mbox->txdone_poll)
602 hrtimer_cancel(&mbox->poll_hrt);
603 }
604}
605EXPORT_SYMBOL_GPL(mbox_controller_unregister);
606
607static void __devm_mbox_controller_unregister(struct device *dev, void *res)
608{
609 struct mbox_controller **mbox = res;
610
611 mbox_controller_unregister(*mbox);
612}
613
614/**
615 * devm_mbox_controller_register() - managed mbox_controller_register()
616 * @dev: device owning the mailbox controller being registered
617 * @mbox: mailbox controller being registered
618 *
619 * This function adds a device-managed resource that will make sure that the
620 * mailbox controller, which is registered using mbox_controller_register()
621 * as part of this function, will be unregistered along with the rest of
622 * device-managed resources upon driver probe failure or driver removal.
623 *
624 * Returns 0 on success or a negative error code on failure.
625 */
626int devm_mbox_controller_register(struct device *dev,
627 struct mbox_controller *mbox)
628{
629 struct mbox_controller **ptr;
630 int err;
631
632 ptr = devres_alloc(__devm_mbox_controller_unregister, sizeof(*ptr),
633 GFP_KERNEL);
634 if (!ptr)
635 return -ENOMEM;
636
637 err = mbox_controller_register(mbox);
638 if (err < 0) {
639 devres_free(ptr);
640 return err;
641 }
642
643 devres_add(dev, ptr);
644 *ptr = mbox;
645
646 return 0;
647}
648EXPORT_SYMBOL_GPL(devm_mbox_controller_register);
649
650#ifdef CONFIG_DEBUG_FS
651static void *mbox_seq_start(struct seq_file *s, loff_t *pos)
652{
653 mutex_lock(&con_mutex);
654 return seq_list_start(&mbox_cons, *pos);
655}
656
657static void *mbox_seq_next(struct seq_file *s, void *v, loff_t *pos)
658{
659 return seq_list_next(v, &mbox_cons, pos);
660}
661
662static void mbox_seq_stop(struct seq_file *s, void *v)
663{
664 mutex_unlock(&con_mutex);
665}
666
667static int mbox_seq_show(struct seq_file *seq, void *v)
668{
669 const struct mbox_controller *mbox = list_entry(v, struct mbox_controller, node);
670
671 seq_printf(seq, "%s:\n", dev_name(mbox->dev));
672
673 for (unsigned int i = 0; i < mbox->num_chans; i++) {
674 struct mbox_chan *chan = &mbox->chans[i];
675
676 scoped_guard(spinlock_irqsave, &chan->lock) {
677 if (chan->cl) {
678 struct device *cl_dev = chan->cl->dev;
679
680 seq_printf(seq, " %3u: %s\n", i,
681 cl_dev ? dev_name(cl_dev) : "NULL device");
682 }
683 }
684 }
685
686 return 0;
687}
688
689static const struct seq_operations mbox_sops = {
690 .start = mbox_seq_start,
691 .next = mbox_seq_next,
692 .stop = mbox_seq_stop,
693 .show = mbox_seq_show,
694};
695DEFINE_SEQ_ATTRIBUTE(mbox);
696
697/*
698 * subsys_initcall() is used here but controllers may already have been
699 * registered earlier or will be later. The rationale is that debugfs is
700 * accessed only late, i.e. from userspace. So, files created here must make no
701 * assumptions about initcall ordering.
702 */
703static int __init mbox_init(void)
704{
705 struct dentry *mbox_debugfs = debugfs_create_dir("mailbox", NULL);
706
707 debugfs_create_file("mailbox_summary", 0444, mbox_debugfs, NULL, &mbox_fops);
708 return 0;
709}
710subsys_initcall(mbox_init);
711#endif /* DEBUG_FS */