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 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/slab.h>
15
16#include "common.h"
17
18/**
19 * struct scmi_mailbox - Structure representing a SCMI mailbox transport
20 *
21 * @cl: Mailbox Client
22 * @chan: Transmit/Receive mailbox uni/bi-directional channel
23 * @chan_receiver: Optional Receiver mailbox unidirectional channel
24 * @cinfo: SCMI channel info
25 * @shmem: Transmit/Receive shared memory area
26 */
27struct scmi_mailbox {
28	struct mbox_client cl;
29	struct mbox_chan *chan;
30	struct mbox_chan *chan_receiver;
31	struct scmi_chan_info *cinfo;
32	struct scmi_shared_mem __iomem *shmem;
33};
34
35#define client_to_scmi_mailbox(c) container_of(c, struct scmi_mailbox, cl)
36
37static void tx_prepare(struct mbox_client *cl, void *m)
38{
39	struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
40
41	shmem_tx_prepare(smbox->shmem, m, smbox->cinfo);
42}
43
44static void rx_callback(struct mbox_client *cl, void *m)
45{
46	struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
47
48	/*
49	 * An A2P IRQ is NOT valid when received while the platform still has
50	 * the ownership of the channel, because the platform at first releases
51	 * the SMT channel and then sends the completion interrupt.
52	 *
53	 * This addresses a possible race condition in which a spurious IRQ from
54	 * a previous timed-out reply which arrived late could be wrongly
55	 * associated with the next pending transaction.
56	 */
57	if (cl->knows_txdone && !shmem_channel_free(smbox->shmem)) {
58		dev_warn(smbox->cinfo->dev, "Ignoring spurious A2P IRQ !\n");
59		return;
60	}
61
62	scmi_rx_callback(smbox->cinfo, shmem_read_header(smbox->shmem), NULL);
63}
64
65static bool mailbox_chan_available(struct device_node *of_node, int idx)
66{
67	int num_mb;
68
69	/*
70	 * Just check if bidirrectional channels are involved, and check the
71	 * index accordingly; proper full validation will be made later
72	 * in mailbox_chan_setup().
73	 */
74	num_mb = of_count_phandle_with_args(of_node, "mboxes", "#mbox-cells");
75	if (num_mb == 3 && idx == 1)
76		idx = 2;
77
78	return !of_parse_phandle_with_args(of_node, "mboxes",
79					   "#mbox-cells", idx, NULL);
80}
81
82/**
83 * mailbox_chan_validate  - Validate transport configuration and map channels
84 *
85 * @cdev: Reference to the underlying transport device carrying the
86 *	  of_node descriptor to analyze.
87 * @a2p_rx_chan: A reference to an optional unidirectional channel to use
88 *		 for replies on the a2p channel. Set as zero if not present.
89 * @p2a_chan: A reference to the optional p2a channel.
90 *	      Set as zero if not present.
91 *
92 * At first, validate the transport configuration as described in terms of
93 * 'mboxes' and 'shmem', then determin which mailbox channel indexes are
94 * appropriate to be use in the current configuration.
95 *
96 * Return: 0 on Success or error
97 */
98static int mailbox_chan_validate(struct device *cdev,
99				 int *a2p_rx_chan, int *p2a_chan)
100{
101	int num_mb, num_sh, ret = 0;
102	struct device_node *np = cdev->of_node;
103
104	num_mb = of_count_phandle_with_args(np, "mboxes", "#mbox-cells");
105	num_sh = of_count_phandle_with_args(np, "shmem", NULL);
106	dev_dbg(cdev, "Found %d mboxes and %d shmems !\n", num_mb, num_sh);
107
108	/* Bail out if mboxes and shmem descriptors are inconsistent */
109	if (num_mb <= 0 || num_sh <= 0 || num_sh > 2 || num_mb > 3 ||
110	    (num_mb == 1 && num_sh != 1) || (num_mb == 3 && num_sh != 2)) {
111		dev_warn(cdev,
112			 "Invalid channel descriptor for '%s' - mbs:%d  shm:%d\n",
113			 of_node_full_name(np), num_mb, num_sh);
114		return -EINVAL;
115	}
116
117	/* Bail out if provided shmem descriptors do not refer distinct areas  */
118	if (num_sh > 1) {
119		struct device_node *np_tx, *np_rx;
120
121		np_tx = of_parse_phandle(np, "shmem", 0);
122		np_rx = of_parse_phandle(np, "shmem", 1);
123		if (!np_tx || !np_rx || np_tx == np_rx) {
124			dev_warn(cdev, "Invalid shmem descriptor for '%s'\n",
125				 of_node_full_name(np));
126			ret = -EINVAL;
127		}
128
129		of_node_put(np_tx);
130		of_node_put(np_rx);
131	}
132
133	/* Calculate channels IDs to use depending on mboxes/shmem layout */
134	if (!ret) {
135		switch (num_mb) {
136		case 1:
137			*a2p_rx_chan = 0;
138			*p2a_chan = 0;
139			break;
140		case 2:
141			if (num_sh == 2) {
142				*a2p_rx_chan = 0;
143				*p2a_chan = 1;
144			} else {
145				*a2p_rx_chan = 1;
146				*p2a_chan = 0;
147			}
148			break;
149		case 3:
150			*a2p_rx_chan = 1;
151			*p2a_chan = 2;
152			break;
153		}
154	}
155
156	return ret;
157}
158
159static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
160			      bool tx)
161{
162	const char *desc = tx ? "Tx" : "Rx";
163	struct device *cdev = cinfo->dev;
164	struct scmi_mailbox *smbox;
165	struct device_node *shmem;
166	int ret, a2p_rx_chan, p2a_chan, idx = tx ? 0 : 1;
167	struct mbox_client *cl;
168	resource_size_t size;
169	struct resource res;
170
171	ret = mailbox_chan_validate(cdev, &a2p_rx_chan, &p2a_chan);
172	if (ret)
173		return ret;
174
175	if (!tx && !p2a_chan)
176		return -ENODEV;
177
178	smbox = devm_kzalloc(dev, sizeof(*smbox), GFP_KERNEL);
179	if (!smbox)
180		return -ENOMEM;
181
182	shmem = of_parse_phandle(cdev->of_node, "shmem", idx);
183	if (!of_device_is_compatible(shmem, "arm,scmi-shmem")) {
184		of_node_put(shmem);
185		return -ENXIO;
186	}
187
188	ret = of_address_to_resource(shmem, 0, &res);
189	of_node_put(shmem);
190	if (ret) {
191		dev_err(cdev, "failed to get SCMI %s shared memory\n", desc);
192		return ret;
193	}
194
195	size = resource_size(&res);
196	smbox->shmem = devm_ioremap(dev, res.start, size);
197	if (!smbox->shmem) {
198		dev_err(dev, "failed to ioremap SCMI %s shared memory\n", desc);
199		return -EADDRNOTAVAIL;
200	}
201
202	cl = &smbox->cl;
203	cl->dev = cdev;
204	cl->tx_prepare = tx ? tx_prepare : NULL;
205	cl->rx_callback = rx_callback;
206	cl->tx_block = false;
207	cl->knows_txdone = tx;
208
209	smbox->chan = mbox_request_channel(cl, tx ? 0 : p2a_chan);
210	if (IS_ERR(smbox->chan)) {
211		ret = PTR_ERR(smbox->chan);
212		if (ret != -EPROBE_DEFER)
213			dev_err(cdev,
214				"failed to request SCMI %s mailbox\n", desc);
215		return ret;
216	}
217
218	/* Additional unidirectional channel for TX if needed */
219	if (tx && a2p_rx_chan) {
220		smbox->chan_receiver = mbox_request_channel(cl, a2p_rx_chan);
221		if (IS_ERR(smbox->chan_receiver)) {
222			ret = PTR_ERR(smbox->chan_receiver);
223			if (ret != -EPROBE_DEFER)
224				dev_err(cdev, "failed to request SCMI Tx Receiver mailbox\n");
225			return ret;
226		}
227	}
228
229	cinfo->transport_info = smbox;
230	smbox->cinfo = cinfo;
231
232	return 0;
233}
234
235static int mailbox_chan_free(int id, void *p, void *data)
236{
237	struct scmi_chan_info *cinfo = p;
238	struct scmi_mailbox *smbox = cinfo->transport_info;
239
240	if (smbox && !IS_ERR(smbox->chan)) {
241		mbox_free_channel(smbox->chan);
242		mbox_free_channel(smbox->chan_receiver);
243		cinfo->transport_info = NULL;
244		smbox->chan = NULL;
245		smbox->chan_receiver = NULL;
246		smbox->cinfo = NULL;
247	}
248
249	return 0;
250}
251
252static int mailbox_send_message(struct scmi_chan_info *cinfo,
253				struct scmi_xfer *xfer)
254{
255	struct scmi_mailbox *smbox = cinfo->transport_info;
256	int ret;
257
258	ret = mbox_send_message(smbox->chan, xfer);
259
260	/* mbox_send_message returns non-negative value on success, so reset */
261	if (ret > 0)
262		ret = 0;
263
264	return ret;
265}
266
267static void mailbox_mark_txdone(struct scmi_chan_info *cinfo, int ret,
268				struct scmi_xfer *__unused)
269{
270	struct scmi_mailbox *smbox = cinfo->transport_info;
271
272	/*
273	 * NOTE: we might prefer not to need the mailbox ticker to manage the
274	 * transfer queueing since the protocol layer queues things by itself.
275	 * Unfortunately, we have to kick the mailbox framework after we have
276	 * received our message.
277	 */
278	mbox_client_txdone(smbox->chan, ret);
279}
280
281static void mailbox_fetch_response(struct scmi_chan_info *cinfo,
282				   struct scmi_xfer *xfer)
283{
284	struct scmi_mailbox *smbox = cinfo->transport_info;
285
286	shmem_fetch_response(smbox->shmem, xfer);
287}
288
289static void mailbox_fetch_notification(struct scmi_chan_info *cinfo,
290				       size_t max_len, struct scmi_xfer *xfer)
291{
292	struct scmi_mailbox *smbox = cinfo->transport_info;
293
294	shmem_fetch_notification(smbox->shmem, max_len, xfer);
295}
296
297static void mailbox_clear_channel(struct scmi_chan_info *cinfo)
298{
299	struct scmi_mailbox *smbox = cinfo->transport_info;
300
301	shmem_clear_channel(smbox->shmem);
302}
303
304static bool
305mailbox_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
306{
307	struct scmi_mailbox *smbox = cinfo->transport_info;
308
309	return shmem_poll_done(smbox->shmem, xfer);
310}
311
312static const struct scmi_transport_ops scmi_mailbox_ops = {
313	.chan_available = mailbox_chan_available,
314	.chan_setup = mailbox_chan_setup,
315	.chan_free = mailbox_chan_free,
316	.send_message = mailbox_send_message,
317	.mark_txdone = mailbox_mark_txdone,
318	.fetch_response = mailbox_fetch_response,
319	.fetch_notification = mailbox_fetch_notification,
320	.clear_channel = mailbox_clear_channel,
321	.poll_done = mailbox_poll_done,
322};
323
324const struct scmi_desc scmi_mailbox_desc = {
325	.ops = &scmi_mailbox_ops,
326	.max_rx_timeout_ms = 30, /* We may increase this if required */
327	.max_msg = 20, /* Limited by MBOX_TX_QUEUE_LEN */
328	.max_msg_size = 128,
329};
330