mailbox.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * System Control and Management Interface (SCMI) Message Mailbox Transport
  4 * driver.
  5 *
  6 * Copyright (C) 2019-2024 ARM Ltd.
  7 */
  8
  9#include <linux/err.h>
 10#include <linux/device.h>
 11#include <linux/mailbox_client.h>
 12#include <linux/of.h>
 13#include <linux/of_address.h>
 14#include <linux/platform_device.h>
 15#include <linux/slab.h>
 16
 17#include "../common.h"
 18
 19/**
 20 * struct scmi_mailbox - Structure representing a SCMI mailbox transport
 21 *
 22 * @cl: Mailbox Client
 23 * @chan: Transmit/Receive mailbox uni/bi-directional channel
 24 * @chan_receiver: Optional Receiver mailbox unidirectional channel
 25 * @chan_platform_receiver: Optional Platform Receiver mailbox unidirectional channel
 26 * @cinfo: SCMI channel info
 27 * @shmem: Transmit/Receive shared memory area
 28 * @chan_lock: Lock that prevents multiple xfers from being queued
 29 * @io_ops: Transport specific I/O operations
 30 */
 31struct scmi_mailbox {
 32	struct mbox_client cl;
 33	struct mbox_chan *chan;
 34	struct mbox_chan *chan_receiver;
 35	struct mbox_chan *chan_platform_receiver;
 36	struct scmi_chan_info *cinfo;
 37	struct scmi_shared_mem __iomem *shmem;
 38	struct mutex chan_lock;
 39	struct scmi_shmem_io_ops *io_ops;
 40};
 41
 42#define client_to_scmi_mailbox(c) container_of(c, struct scmi_mailbox, cl)
 43
 44static struct scmi_transport_core_operations *core;
 45
 46static void tx_prepare(struct mbox_client *cl, void *m)
 47{
 48	struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
 49
 50	core->shmem->tx_prepare(smbox->shmem, m, smbox->cinfo,
 51				smbox->io_ops->toio);
 52}
 53
 54static void rx_callback(struct mbox_client *cl, void *m)
 55{
 56	struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
 57
 58	/*
 59	 * An A2P IRQ is NOT valid when received while the platform still has
 60	 * the ownership of the channel, because the platform at first releases
 61	 * the SMT channel and then sends the completion interrupt.
 62	 *
 63	 * This addresses a possible race condition in which a spurious IRQ from
 64	 * a previous timed-out reply which arrived late could be wrongly
 65	 * associated with the next pending transaction.
 66	 */
 67	if (cl->knows_txdone &&
 68	    !core->shmem->channel_free(smbox->shmem)) {
 69		dev_warn(smbox->cinfo->dev, "Ignoring spurious A2P IRQ !\n");
 70		core->bad_message_trace(smbox->cinfo,
 71			     core->shmem->read_header(smbox->shmem),
 72							     MSG_MBOX_SPURIOUS);
 73		return;
 74	}
 75
 76	core->rx_callback(smbox->cinfo,
 77		      core->shmem->read_header(smbox->shmem), NULL);
 78}
 79
 80static bool mailbox_chan_available(struct device_node *of_node, int idx)
 81{
 82	int num_mb;
 83
 84	/*
 85	 * Just check if bidirrectional channels are involved, and check the
 86	 * index accordingly; proper full validation will be made later
 87	 * in mailbox_chan_setup().
 88	 */
 89	num_mb = of_count_phandle_with_args(of_node, "mboxes", "#mbox-cells");
 90	if (num_mb == 3 && idx == 1)
 91		idx = 2;
 92
 93	return !of_parse_phandle_with_args(of_node, "mboxes",
 94					   "#mbox-cells", idx, NULL);
 95}
 96
 97/**
 98 * mailbox_chan_validate  - Validate transport configuration and map channels
 99 *
100 * @cdev: Reference to the underlying transport device carrying the
101 *	  of_node descriptor to analyze.
102 * @a2p_rx_chan: A reference to an optional unidirectional channel to use
103 *		 for replies on the a2p channel. Set as zero if not present.
104 * @p2a_chan: A reference to the optional p2a channel.
105 *	      Set as zero if not present.
106 * @p2a_rx_chan: A reference to the optional p2a completion channel.
107 *	      Set as zero if not present.
108 *
109 * At first, validate the transport configuration as described in terms of
110 * 'mboxes' and 'shmem', then determin which mailbox channel indexes are
111 * appropriate to be use in the current configuration.
112 *
113 * Return: 0 on Success or error
114 */
115static int mailbox_chan_validate(struct device *cdev, int *a2p_rx_chan,
116				 int *p2a_chan, int *p2a_rx_chan)
117{
118	int num_mb, num_sh, ret = 0;
119	struct device_node *np = cdev->of_node;
120
121	num_mb = of_count_phandle_with_args(np, "mboxes", "#mbox-cells");
122	num_sh = of_count_phandle_with_args(np, "shmem", NULL);
123	dev_dbg(cdev, "Found %d mboxes and %d shmems !\n", num_mb, num_sh);
124
125	/* Bail out if mboxes and shmem descriptors are inconsistent */
126	if (num_mb <= 0 || num_sh <= 0 || num_sh > 2 || num_mb > 4 ||
127	    (num_mb == 1 && num_sh != 1) || (num_mb == 3 && num_sh != 2) ||
128	    (num_mb == 4 && num_sh != 2)) {
129		dev_warn(cdev,
130			 "Invalid channel descriptor for '%pOF' - mbs:%d  shm:%d\n",
131			 np, num_mb, num_sh);
132		return -EINVAL;
133	}
134
135	/* Bail out if provided shmem descriptors do not refer distinct areas  */
136	if (num_sh > 1) {
137		struct device_node *np_tx __free(device_node) =
138					of_parse_phandle(np, "shmem", 0);
139		struct device_node *np_rx __free(device_node) =
140					of_parse_phandle(np, "shmem", 1);
141
142		if (!np_tx || !np_rx || np_tx == np_rx) {
143			dev_warn(cdev, "Invalid shmem descriptor for '%pOF'\n", np);
144			ret = -EINVAL;
145		}
146	}
147
148	/* Calculate channels IDs to use depending on mboxes/shmem layout */
149	if (!ret) {
150		switch (num_mb) {
151		case 1:
152			*a2p_rx_chan = 0;
153			*p2a_chan = 0;
154			*p2a_rx_chan = 0;
155			break;
156		case 2:
157			if (num_sh == 2) {
158				*a2p_rx_chan = 0;
159				*p2a_chan = 1;
160			} else {
161				*a2p_rx_chan = 1;
162				*p2a_chan = 0;
163			}
164			*p2a_rx_chan = 0;
165			break;
166		case 3:
167			*a2p_rx_chan = 1;
168			*p2a_chan = 2;
169			*p2a_rx_chan = 0;
170			break;
171		case 4:
172			*a2p_rx_chan = 1;
173			*p2a_chan = 2;
174			*p2a_rx_chan = 3;
175			break;
176		}
177	}
178
179	return ret;
180}
181
182static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
183			      bool tx)
184{
185	const char *desc = tx ? "Tx" : "Rx";
186	struct device *cdev = cinfo->dev;
187	struct scmi_mailbox *smbox;
188	int ret, a2p_rx_chan, p2a_chan, p2a_rx_chan;
189	struct mbox_client *cl;
190
191	ret = mailbox_chan_validate(cdev, &a2p_rx_chan, &p2a_chan, &p2a_rx_chan);
192	if (ret)
193		return ret;
194
195	if (!tx && !p2a_chan)
196		return -ENODEV;
197
198	smbox = devm_kzalloc(dev, sizeof(*smbox), GFP_KERNEL);
199	if (!smbox)
200		return -ENOMEM;
201
202	smbox->shmem = core->shmem->setup_iomap(cinfo, dev, tx, NULL,
203						&smbox->io_ops);
204	if (IS_ERR(smbox->shmem))
205		return PTR_ERR(smbox->shmem);
206
207	cl = &smbox->cl;
208	cl->dev = cdev;
209	cl->tx_prepare = tx ? tx_prepare : NULL;
210	cl->rx_callback = rx_callback;
211	cl->tx_block = false;
212	cl->knows_txdone = tx;
213
214	smbox->chan = mbox_request_channel(cl, tx ? 0 : p2a_chan);
215	if (IS_ERR(smbox->chan)) {
216		ret = PTR_ERR(smbox->chan);
217		if (ret != -EPROBE_DEFER)
218			dev_err(cdev,
219				"failed to request SCMI %s mailbox\n", desc);
220		return ret;
221	}
222
223	/* Additional unidirectional channel for TX if needed */
224	if (tx && a2p_rx_chan) {
225		smbox->chan_receiver = mbox_request_channel(cl, a2p_rx_chan);
226		if (IS_ERR(smbox->chan_receiver)) {
227			ret = PTR_ERR(smbox->chan_receiver);
228			if (ret != -EPROBE_DEFER)
229				dev_err(cdev, "failed to request SCMI Tx Receiver mailbox\n");
230			return ret;
231		}
232	}
233
234	if (!tx && p2a_rx_chan) {
235		smbox->chan_platform_receiver = mbox_request_channel(cl, p2a_rx_chan);
236		if (IS_ERR(smbox->chan_platform_receiver)) {
237			ret = PTR_ERR(smbox->chan_platform_receiver);
238			if (ret != -EPROBE_DEFER)
239				dev_err(cdev, "failed to request SCMI P2A Receiver mailbox\n");
240			return ret;
241		}
242	}
243
244	cinfo->transport_info = smbox;
245	smbox->cinfo = cinfo;
246	mutex_init(&smbox->chan_lock);
247
248	return 0;
249}
250
251static int mailbox_chan_free(int id, void *p, void *data)
252{
253	struct scmi_chan_info *cinfo = p;
254	struct scmi_mailbox *smbox = cinfo->transport_info;
255
256	if (smbox && !IS_ERR(smbox->chan)) {
257		mbox_free_channel(smbox->chan);
258		mbox_free_channel(smbox->chan_receiver);
259		mbox_free_channel(smbox->chan_platform_receiver);
260		cinfo->transport_info = NULL;
261		smbox->chan = NULL;
262		smbox->chan_receiver = NULL;
263		smbox->chan_platform_receiver = NULL;
264		smbox->cinfo = NULL;
265	}
266
267	return 0;
268}
269
270static int mailbox_send_message(struct scmi_chan_info *cinfo,
271				struct scmi_xfer *xfer)
272{
273	struct scmi_mailbox *smbox = cinfo->transport_info;
274	int ret;
275
276	/*
277	 * The mailbox layer has its own queue. However the mailbox queue
278	 * confuses the per message SCMI timeouts since the clock starts when
279	 * the message is submitted into the mailbox queue. So when multiple
280	 * messages are queued up the clock starts on all messages instead of
281	 * only the one inflight.
282	 */
283	mutex_lock(&smbox->chan_lock);
284
285	ret = mbox_send_message(smbox->chan, xfer);
286	/* mbox_send_message returns non-negative value on success */
287	if (ret < 0) {
288		mutex_unlock(&smbox->chan_lock);
289		return ret;
290	}
291
292	return 0;
293}
294
295static void mailbox_mark_txdone(struct scmi_chan_info *cinfo, int ret,
296				struct scmi_xfer *__unused)
297{
298	struct scmi_mailbox *smbox = cinfo->transport_info;
299
300	mbox_client_txdone(smbox->chan, ret);
301
302	/* Release channel */
303	mutex_unlock(&smbox->chan_lock);
304}
305
306static void mailbox_fetch_response(struct scmi_chan_info *cinfo,
307				   struct scmi_xfer *xfer)
308{
309	struct scmi_mailbox *smbox = cinfo->transport_info;
310
311	core->shmem->fetch_response(smbox->shmem, xfer, smbox->io_ops->fromio);
312}
313
314static void mailbox_fetch_notification(struct scmi_chan_info *cinfo,
315				       size_t max_len, struct scmi_xfer *xfer)
316{
317	struct scmi_mailbox *smbox = cinfo->transport_info;
318
319	core->shmem->fetch_notification(smbox->shmem, max_len, xfer,
320					smbox->io_ops->fromio);
321}
322
323static void mailbox_clear_channel(struct scmi_chan_info *cinfo)
324{
325	struct scmi_mailbox *smbox = cinfo->transport_info;
326	struct mbox_chan *intr_chan;
327	int ret;
328
329	core->shmem->clear_channel(smbox->shmem);
330
331	if (!core->shmem->channel_intr_enabled(smbox->shmem))
332		return;
333
334	if (smbox->chan_platform_receiver)
335		intr_chan = smbox->chan_platform_receiver;
336	else if (smbox->chan)
337		intr_chan = smbox->chan;
338	else
339		return;
340
341	ret = mbox_send_message(intr_chan, NULL);
342	/* mbox_send_message returns non-negative value on success, so reset */
343	if (ret > 0)
344		ret = 0;
345
346	mbox_client_txdone(intr_chan, ret);
347}
348
349static bool
350mailbox_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
351{
352	struct scmi_mailbox *smbox = cinfo->transport_info;
353
354	return core->shmem->poll_done(smbox->shmem, xfer);
355}
356
357static const struct scmi_transport_ops scmi_mailbox_ops = {
358	.chan_available = mailbox_chan_available,
359	.chan_setup = mailbox_chan_setup,
360	.chan_free = mailbox_chan_free,
361	.send_message = mailbox_send_message,
362	.mark_txdone = mailbox_mark_txdone,
363	.fetch_response = mailbox_fetch_response,
364	.fetch_notification = mailbox_fetch_notification,
365	.clear_channel = mailbox_clear_channel,
366	.poll_done = mailbox_poll_done,
367};
368
369static struct scmi_desc scmi_mailbox_desc = {
370	.ops = &scmi_mailbox_ops,
371	.max_rx_timeout_ms = 30, /* We may increase this if required */
372	.max_msg = 20, /* Limited by MBOX_TX_QUEUE_LEN */
373	.max_msg_size = SCMI_SHMEM_MAX_PAYLOAD_SIZE,
374};
375
376static const struct of_device_id scmi_of_match[] = {
377	{ .compatible = "arm,scmi" },
378	{ /* Sentinel */ },
379};
380MODULE_DEVICE_TABLE(of, scmi_of_match);
381
382DEFINE_SCMI_TRANSPORT_DRIVER(scmi_mailbox, scmi_mailbox_driver,
383			     scmi_mailbox_desc, scmi_of_match, core);
384module_platform_driver(scmi_mailbox_driver);
385
386MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
387MODULE_DESCRIPTION("SCMI Mailbox Transport driver");
388MODULE_LICENSE("GPL");