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(shmem: smbox->shmem, xfer: m, cinfo: 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(shmem: smbox->shmem)) {
58 dev_warn(smbox->cinfo->dev, "Ignoring spurious A2P IRQ !\n");
59 return;
60 }
61
62 scmi_rx_callback(cinfo: smbox->cinfo, msg_hdr: shmem_read_header(shmem: 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(np: of_node, list_name: "mboxes", cells_name: "#mbox-cells");
75 if (num_mb == 3 && idx == 1)
76 idx = 2;
77
78 return !of_parse_phandle_with_args(np: of_node, list_name: "mboxes",
79 cells_name: "#mbox-cells", index: 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, list_name: "mboxes", cells_name: "#mbox-cells");
105 num_sh = of_count_phandle_with_args(np, list_name: "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, phandle_name: "shmem", index: 0);
122 np_rx = of_parse_phandle(np, phandle_name: "shmem", index: 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(node: np_tx);
130 of_node_put(node: 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: &a2p_rx_chan, p2a_chan: &p2a_chan);
172 if (ret)
173 return ret;
174
175 if (!tx && !p2a_chan)
176 return -ENODEV;
177
178 smbox = devm_kzalloc(dev, size: sizeof(*smbox), GFP_KERNEL);
179 if (!smbox)
180 return -ENOMEM;
181
182 shmem = of_parse_phandle(np: cdev->of_node, phandle_name: "shmem", index: idx);
183 if (!of_device_is_compatible(device: shmem, "arm,scmi-shmem")) {
184 of_node_put(node: shmem);
185 return -ENXIO;
186 }
187
188 ret = of_address_to_resource(dev: shmem, index: 0, r: &res);
189 of_node_put(node: 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: &res);
196 smbox->shmem = devm_ioremap(dev, offset: 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, index: tx ? 0 : p2a_chan);
210 if (IS_ERR(ptr: smbox->chan)) {
211 ret = PTR_ERR(ptr: 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, index: a2p_rx_chan);
221 if (IS_ERR(ptr: smbox->chan_receiver)) {
222 ret = PTR_ERR(ptr: 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(ptr: smbox->chan)) {
241 mbox_free_channel(chan: smbox->chan);
242 mbox_free_channel(chan: 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(chan: smbox->chan, mssg: 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(chan: smbox->chan, r: 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(shmem: 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(shmem: 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(shmem: 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(shmem: 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

source code of linux/drivers/firmware/arm_scmi/mailbox.c