1/*
2 * Mailbox: Common code for Mailbox controllers and users
3 *
4 * Copyright (C) 2013-2014 Linaro Ltd.
5 * Author: Jassi Brar <jassisinghbrar@gmail.com>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
11
12#include <linux/interrupt.h>
13#include <linux/spinlock.h>
14#include <linux/mutex.h>
15#include <linux/delay.h>
16#include <linux/slab.h>
17#include <linux/err.h>
18#include <linux/module.h>
19#include <linux/device.h>
20#include <linux/bitops.h>
21#include <linux/mailbox_client.h>
22#include <linux/mailbox_controller.h>
23
24#include "mailbox.h"
25
26static LIST_HEAD(mbox_cons);
27static DEFINE_MUTEX(con_mutex);
28
29static void poll_txdone(unsigned long data);
30
31static int add_to_rbuf(struct mbox_chan *chan, void *mssg)
32{
33	int idx;
34	unsigned long flags;
35
36	spin_lock_irqsave(&chan->lock, flags);
37
38	/* See if there is any space left */
39	if (chan->msg_count == MBOX_TX_QUEUE_LEN) {
40		spin_unlock_irqrestore(&chan->lock, flags);
41		return -ENOBUFS;
42	}
43
44	idx = chan->msg_free;
45	chan->msg_data[idx] = mssg;
46	chan->msg_count++;
47
48	if (idx == MBOX_TX_QUEUE_LEN - 1)
49		chan->msg_free = 0;
50	else
51		chan->msg_free++;
52
53	spin_unlock_irqrestore(&chan->lock, flags);
54
55	return idx;
56}
57
58static void msg_submit(struct mbox_chan *chan)
59{
60	unsigned count, idx;
61	unsigned long flags;
62	void *data;
63	int err = -EBUSY;
64
65	spin_lock_irqsave(&chan->lock, flags);
66
67	if (!chan->msg_count || chan->active_req)
68		goto exit;
69
70	count = chan->msg_count;
71	idx = chan->msg_free;
72	if (idx >= count)
73		idx -= count;
74	else
75		idx += MBOX_TX_QUEUE_LEN - count;
76
77	data = chan->msg_data[idx];
78
79	if (chan->cl->tx_prepare)
80		chan->cl->tx_prepare(chan->cl, data);
81	/* Try to submit a message to the MBOX controller */
82	err = chan->mbox->ops->send_data(chan, data);
83	if (!err) {
84		chan->active_req = data;
85		chan->msg_count--;
86	}
87exit:
88	spin_unlock_irqrestore(&chan->lock, flags);
89
90	if (!err && (chan->txdone_method & TXDONE_BY_POLL))
91		poll_txdone((unsigned long)chan->mbox);
92}
93
94static void tx_tick(struct mbox_chan *chan, int r)
95{
96	unsigned long flags;
97	void *mssg;
98
99	spin_lock_irqsave(&chan->lock, flags);
100	mssg = chan->active_req;
101	chan->active_req = NULL;
102	spin_unlock_irqrestore(&chan->lock, flags);
103
104	/* Submit next message */
105	msg_submit(chan);
106
107	/* Notify the client */
108	if (mssg && chan->cl->tx_done)
109		chan->cl->tx_done(chan->cl, mssg, r);
110
111	if (chan->cl->tx_block)
112		complete(&chan->tx_complete);
113}
114
115static void poll_txdone(unsigned long data)
116{
117	struct mbox_controller *mbox = (struct mbox_controller *)data;
118	bool txdone, resched = false;
119	int i;
120
121	for (i = 0; i < mbox->num_chans; i++) {
122		struct mbox_chan *chan = &mbox->chans[i];
123
124		if (chan->active_req && chan->cl) {
125			txdone = chan->mbox->ops->last_tx_done(chan);
126			if (txdone)
127				tx_tick(chan, 0);
128			else
129				resched = true;
130		}
131	}
132
133	if (resched)
134		mod_timer(&mbox->poll, jiffies +
135				msecs_to_jiffies(mbox->txpoll_period));
136}
137
138/**
139 * mbox_chan_received_data - A way for controller driver to push data
140 *				received from remote to the upper layer.
141 * @chan: Pointer to the mailbox channel on which RX happened.
142 * @mssg: Client specific message typecasted as void *
143 *
144 * After startup and before shutdown any data received on the chan
145 * is passed on to the API via atomic mbox_chan_received_data().
146 * The controller should ACK the RX only after this call returns.
147 */
148void mbox_chan_received_data(struct mbox_chan *chan, void *mssg)
149{
150	/* No buffering the received data */
151	if (chan->cl->rx_callback)
152		chan->cl->rx_callback(chan->cl, mssg);
153}
154EXPORT_SYMBOL_GPL(mbox_chan_received_data);
155
156/**
157 * mbox_chan_txdone - A way for controller driver to notify the
158 *			framework that the last TX has completed.
159 * @chan: Pointer to the mailbox chan on which TX happened.
160 * @r: Status of last TX - OK or ERROR
161 *
162 * The controller that has IRQ for TX ACK calls this atomic API
163 * to tick the TX state machine. It works only if txdone_irq
164 * is set by the controller.
165 */
166void mbox_chan_txdone(struct mbox_chan *chan, int r)
167{
168	if (unlikely(!(chan->txdone_method & TXDONE_BY_IRQ))) {
169		dev_err(chan->mbox->dev,
170		       "Controller can't run the TX ticker\n");
171		return;
172	}
173
174	tx_tick(chan, r);
175}
176EXPORT_SYMBOL_GPL(mbox_chan_txdone);
177
178/**
179 * mbox_client_txdone - The way for a client to run the TX state machine.
180 * @chan: Mailbox channel assigned to this client.
181 * @r: Success status of last transmission.
182 *
183 * The client/protocol had received some 'ACK' packet and it notifies
184 * the API that the last packet was sent successfully. This only works
185 * if the controller can't sense TX-Done.
186 */
187void mbox_client_txdone(struct mbox_chan *chan, int r)
188{
189	if (unlikely(!(chan->txdone_method & TXDONE_BY_ACK))) {
190		dev_err(chan->mbox->dev, "Client can't run the TX ticker\n");
191		return;
192	}
193
194	tx_tick(chan, r);
195}
196EXPORT_SYMBOL_GPL(mbox_client_txdone);
197
198/**
199 * mbox_client_peek_data - A way for client driver to pull data
200 *			received from remote by the controller.
201 * @chan: Mailbox channel assigned to this client.
202 *
203 * A poke to controller driver for any received data.
204 * The data is actually passed onto client via the
205 * mbox_chan_received_data()
206 * The call can be made from atomic context, so the controller's
207 * implementation of peek_data() must not sleep.
208 *
209 * Return: True, if controller has, and is going to push after this,
210 *          some data.
211 *         False, if controller doesn't have any data to be read.
212 */
213bool mbox_client_peek_data(struct mbox_chan *chan)
214{
215	if (chan->mbox->ops->peek_data)
216		return chan->mbox->ops->peek_data(chan);
217
218	return false;
219}
220EXPORT_SYMBOL_GPL(mbox_client_peek_data);
221
222/**
223 * mbox_send_message -	For client to submit a message to be
224 *				sent to the remote.
225 * @chan: Mailbox channel assigned to this client.
226 * @mssg: Client specific message typecasted.
227 *
228 * For client to submit data to the controller destined for a remote
229 * processor. If the client had set 'tx_block', the call will return
230 * either when the remote receives the data or when 'tx_tout' millisecs
231 * run out.
232 *  In non-blocking mode, the requests are buffered by the API and a
233 * non-negative token is returned for each queued request. If the request
234 * is not queued, a negative token is returned. Upon failure or successful
235 * TX, the API calls 'tx_done' from atomic context, from which the client
236 * could submit yet another request.
237 * The pointer to message should be preserved until it is sent
238 * over the chan, i.e, tx_done() is made.
239 * This function could be called from atomic context as it simply
240 * queues the data and returns a token against the request.
241 *
242 * Return: Non-negative integer for successful submission (non-blocking mode)
243 *	or transmission over chan (blocking mode).
244 *	Negative value denotes failure.
245 */
246int mbox_send_message(struct mbox_chan *chan, void *mssg)
247{
248	int t;
249
250	if (!chan || !chan->cl)
251		return -EINVAL;
252
253	t = add_to_rbuf(chan, mssg);
254	if (t < 0) {
255		dev_err(chan->mbox->dev, "Try increasing MBOX_TX_QUEUE_LEN\n");
256		return t;
257	}
258
259	msg_submit(chan);
260
261	if (chan->cl->tx_block && chan->active_req) {
262		unsigned long wait;
263		int ret;
264
265		if (!chan->cl->tx_tout) /* wait forever */
266			wait = msecs_to_jiffies(3600000);
267		else
268			wait = msecs_to_jiffies(chan->cl->tx_tout);
269
270		ret = wait_for_completion_timeout(&chan->tx_complete, wait);
271		if (ret == 0) {
272			t = -EIO;
273			tx_tick(chan, -EIO);
274		}
275	}
276
277	return t;
278}
279EXPORT_SYMBOL_GPL(mbox_send_message);
280
281/**
282 * mbox_request_channel - Request a mailbox channel.
283 * @cl: Identity of the client requesting the channel.
284 * @index: Index of mailbox specifier in 'mboxes' property.
285 *
286 * The Client specifies its requirements and capabilities while asking for
287 * a mailbox channel. It can't be called from atomic context.
288 * The channel is exclusively allocated and can't be used by another
289 * client before the owner calls mbox_free_channel.
290 * After assignment, any packet received on this channel will be
291 * handed over to the client via the 'rx_callback'.
292 * The framework holds reference to the client, so the mbox_client
293 * structure shouldn't be modified until the mbox_free_channel returns.
294 *
295 * Return: Pointer to the channel assigned to the client if successful.
296 *		ERR_PTR for request failure.
297 */
298struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index)
299{
300	struct device *dev = cl->dev;
301	struct mbox_controller *mbox;
302	struct of_phandle_args spec;
303	struct mbox_chan *chan;
304	unsigned long flags;
305	int ret;
306
307	if (!dev || !dev->of_node) {
308		pr_debug("%s: No owner device node\n", __func__);
309		return ERR_PTR(-ENODEV);
310	}
311
312	mutex_lock(&con_mutex);
313
314	if (of_parse_phandle_with_args(dev->of_node, "mboxes",
315				       "#mbox-cells", index, &spec)) {
316		dev_dbg(dev, "%s: can't parse \"mboxes\" property\n", __func__);
317		mutex_unlock(&con_mutex);
318		return ERR_PTR(-ENODEV);
319	}
320
321	chan = NULL;
322	list_for_each_entry(mbox, &mbox_cons, node)
323		if (mbox->dev->of_node == spec.np) {
324			chan = mbox->of_xlate(mbox, &spec);
325			break;
326		}
327
328	of_node_put(spec.np);
329
330	if (!chan || chan->cl || !try_module_get(mbox->dev->driver->owner)) {
331		dev_dbg(dev, "%s: mailbox not free\n", __func__);
332		mutex_unlock(&con_mutex);
333		return ERR_PTR(-EBUSY);
334	}
335
336	spin_lock_irqsave(&chan->lock, flags);
337	chan->msg_free = 0;
338	chan->msg_count = 0;
339	chan->active_req = NULL;
340	chan->cl = cl;
341	init_completion(&chan->tx_complete);
342
343	if (chan->txdone_method	== TXDONE_BY_POLL && cl->knows_txdone)
344		chan->txdone_method |= TXDONE_BY_ACK;
345
346	spin_unlock_irqrestore(&chan->lock, flags);
347
348	ret = chan->mbox->ops->startup(chan);
349	if (ret) {
350		dev_err(dev, "Unable to startup the chan (%d)\n", ret);
351		mbox_free_channel(chan);
352		chan = ERR_PTR(ret);
353	}
354
355	mutex_unlock(&con_mutex);
356	return chan;
357}
358EXPORT_SYMBOL_GPL(mbox_request_channel);
359
360/**
361 * mbox_free_channel - The client relinquishes control of a mailbox
362 *			channel by this call.
363 * @chan: The mailbox channel to be freed.
364 */
365void mbox_free_channel(struct mbox_chan *chan)
366{
367	unsigned long flags;
368
369	if (!chan || !chan->cl)
370		return;
371
372	chan->mbox->ops->shutdown(chan);
373
374	/* The queued TX requests are simply aborted, no callbacks are made */
375	spin_lock_irqsave(&chan->lock, flags);
376	chan->cl = NULL;
377	chan->active_req = NULL;
378	if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
379		chan->txdone_method = TXDONE_BY_POLL;
380
381	module_put(chan->mbox->dev->driver->owner);
382	spin_unlock_irqrestore(&chan->lock, flags);
383}
384EXPORT_SYMBOL_GPL(mbox_free_channel);
385
386static struct mbox_chan *
387of_mbox_index_xlate(struct mbox_controller *mbox,
388		    const struct of_phandle_args *sp)
389{
390	int ind = sp->args[0];
391
392	if (ind >= mbox->num_chans)
393		return NULL;
394
395	return &mbox->chans[ind];
396}
397
398/**
399 * mbox_controller_register - Register the mailbox controller
400 * @mbox:	Pointer to the mailbox controller.
401 *
402 * The controller driver registers its communication channels
403 */
404int mbox_controller_register(struct mbox_controller *mbox)
405{
406	int i, txdone;
407
408	/* Sanity check */
409	if (!mbox || !mbox->dev || !mbox->ops || !mbox->num_chans)
410		return -EINVAL;
411
412	if (mbox->txdone_irq)
413		txdone = TXDONE_BY_IRQ;
414	else if (mbox->txdone_poll)
415		txdone = TXDONE_BY_POLL;
416	else /* It has to be ACK then */
417		txdone = TXDONE_BY_ACK;
418
419	if (txdone == TXDONE_BY_POLL) {
420		mbox->poll.function = &poll_txdone;
421		mbox->poll.data = (unsigned long)mbox;
422		init_timer(&mbox->poll);
423	}
424
425	for (i = 0; i < mbox->num_chans; i++) {
426		struct mbox_chan *chan = &mbox->chans[i];
427
428		chan->cl = NULL;
429		chan->mbox = mbox;
430		chan->txdone_method = txdone;
431		spin_lock_init(&chan->lock);
432	}
433
434	if (!mbox->of_xlate)
435		mbox->of_xlate = of_mbox_index_xlate;
436
437	mutex_lock(&con_mutex);
438	list_add_tail(&mbox->node, &mbox_cons);
439	mutex_unlock(&con_mutex);
440
441	return 0;
442}
443EXPORT_SYMBOL_GPL(mbox_controller_register);
444
445/**
446 * mbox_controller_unregister - Unregister the mailbox controller
447 * @mbox:	Pointer to the mailbox controller.
448 */
449void mbox_controller_unregister(struct mbox_controller *mbox)
450{
451	int i;
452
453	if (!mbox)
454		return;
455
456	mutex_lock(&con_mutex);
457
458	list_del(&mbox->node);
459
460	for (i = 0; i < mbox->num_chans; i++)
461		mbox_free_channel(&mbox->chans[i]);
462
463	if (mbox->txdone_poll)
464		del_timer_sync(&mbox->poll);
465
466	mutex_unlock(&con_mutex);
467}
468EXPORT_SYMBOL_GPL(mbox_controller_unregister);
469