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 * @chan_lock: Lock that prevents multiple xfers from being queued
27 */
28 struct scmi_mailbox {
29 struct mbox_client cl;
30 struct mbox_chan *chan;
31 struct mbox_chan *chan_receiver;
32 struct scmi_chan_info *cinfo;
33 struct scmi_shared_mem __iomem *shmem;
34 struct mutex chan_lock;
35 };
36
37 #define client_to_scmi_mailbox(c) container_of(c, struct scmi_mailbox, cl)
38
tx_prepare(struct mbox_client * cl,void * m)39 static void tx_prepare(struct mbox_client *cl, void *m)
40 {
41 struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
42
43 shmem_tx_prepare(smbox->shmem, m, smbox->cinfo);
44 }
45
rx_callback(struct mbox_client * cl,void * m)46 static void rx_callback(struct mbox_client *cl, void *m)
47 {
48 struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
49
50 /*
51 * An A2P IRQ is NOT valid when received while the platform still has
52 * the ownership of the channel, because the platform at first releases
53 * the SMT channel and then sends the completion interrupt.
54 *
55 * This addresses a possible race condition in which a spurious IRQ from
56 * a previous timed-out reply which arrived late could be wrongly
57 * associated with the next pending transaction.
58 */
59 if (cl->knows_txdone && !shmem_channel_free(smbox->shmem)) {
60 dev_warn(smbox->cinfo->dev, "Ignoring spurious A2P IRQ !\n");
61 return;
62 }
63
64 scmi_rx_callback(smbox->cinfo, shmem_read_header(smbox->shmem), NULL);
65 }
66
mailbox_chan_available(struct device_node * of_node,int idx)67 static bool mailbox_chan_available(struct device_node *of_node, int idx)
68 {
69 int num_mb;
70
71 /*
72 * Just check if bidirrectional channels are involved, and check the
73 * index accordingly; proper full validation will be made later
74 * in mailbox_chan_setup().
75 */
76 num_mb = of_count_phandle_with_args(of_node, "mboxes", "#mbox-cells");
77 if (num_mb == 3 && idx == 1)
78 idx = 2;
79
80 return !of_parse_phandle_with_args(of_node, "mboxes",
81 "#mbox-cells", idx, NULL);
82 }
83
84 /**
85 * mailbox_chan_validate - Validate transport configuration and map channels
86 *
87 * @cdev: Reference to the underlying transport device carrying the
88 * of_node descriptor to analyze.
89 * @a2p_rx_chan: A reference to an optional unidirectional channel to use
90 * for replies on the a2p channel. Set as zero if not present.
91 * @p2a_chan: A reference to the optional p2a channel.
92 * Set as zero if not present.
93 *
94 * At first, validate the transport configuration as described in terms of
95 * 'mboxes' and 'shmem', then determin which mailbox channel indexes are
96 * appropriate to be use in the current configuration.
97 *
98 * Return: 0 on Success or error
99 */
mailbox_chan_validate(struct device * cdev,int * a2p_rx_chan,int * p2a_chan)100 static int mailbox_chan_validate(struct device *cdev,
101 int *a2p_rx_chan, int *p2a_chan)
102 {
103 int num_mb, num_sh, ret = 0;
104 struct device_node *np = cdev->of_node;
105
106 num_mb = of_count_phandle_with_args(np, "mboxes", "#mbox-cells");
107 num_sh = of_count_phandle_with_args(np, "shmem", NULL);
108 dev_dbg(cdev, "Found %d mboxes and %d shmems !\n", num_mb, num_sh);
109
110 /* Bail out if mboxes and shmem descriptors are inconsistent */
111 if (num_mb <= 0 || num_sh <= 0 || num_sh > 2 || num_mb > 3 ||
112 (num_mb == 1 && num_sh != 1) || (num_mb == 3 && num_sh != 2)) {
113 dev_warn(cdev,
114 "Invalid channel descriptor for '%s' - mbs:%d shm:%d\n",
115 of_node_full_name(np), num_mb, num_sh);
116 return -EINVAL;
117 }
118
119 /* Bail out if provided shmem descriptors do not refer distinct areas */
120 if (num_sh > 1) {
121 struct device_node *np_tx, *np_rx;
122
123 np_tx = of_parse_phandle(np, "shmem", 0);
124 np_rx = of_parse_phandle(np, "shmem", 1);
125 if (!np_tx || !np_rx || np_tx == np_rx) {
126 dev_warn(cdev, "Invalid shmem descriptor for '%s'\n",
127 of_node_full_name(np));
128 ret = -EINVAL;
129 }
130
131 of_node_put(np_tx);
132 of_node_put(np_rx);
133 }
134
135 /* Calculate channels IDs to use depending on mboxes/shmem layout */
136 if (!ret) {
137 switch (num_mb) {
138 case 1:
139 *a2p_rx_chan = 0;
140 *p2a_chan = 0;
141 break;
142 case 2:
143 if (num_sh == 2) {
144 *a2p_rx_chan = 0;
145 *p2a_chan = 1;
146 } else {
147 *a2p_rx_chan = 1;
148 *p2a_chan = 0;
149 }
150 break;
151 case 3:
152 *a2p_rx_chan = 1;
153 *p2a_chan = 2;
154 break;
155 }
156 }
157
158 return ret;
159 }
160
mailbox_chan_setup(struct scmi_chan_info * cinfo,struct device * dev,bool tx)161 static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
162 bool tx)
163 {
164 const char *desc = tx ? "Tx" : "Rx";
165 struct device *cdev = cinfo->dev;
166 struct scmi_mailbox *smbox;
167 struct device_node *shmem;
168 int ret, a2p_rx_chan, p2a_chan, idx = tx ? 0 : 1;
169 struct mbox_client *cl;
170 resource_size_t size;
171 struct resource res;
172
173 ret = mailbox_chan_validate(cdev, &a2p_rx_chan, &p2a_chan);
174 if (ret)
175 return ret;
176
177 if (!tx && !p2a_chan)
178 return -ENODEV;
179
180 smbox = devm_kzalloc(dev, sizeof(*smbox), GFP_KERNEL);
181 if (!smbox)
182 return -ENOMEM;
183
184 shmem = of_parse_phandle(cdev->of_node, "shmem", idx);
185 if (!of_device_is_compatible(shmem, "arm,scmi-shmem")) {
186 of_node_put(shmem);
187 return -ENXIO;
188 }
189
190 ret = of_address_to_resource(shmem, 0, &res);
191 of_node_put(shmem);
192 if (ret) {
193 dev_err(cdev, "failed to get SCMI %s shared memory\n", desc);
194 return ret;
195 }
196
197 size = resource_size(&res);
198 smbox->shmem = devm_ioremap(dev, res.start, size);
199 if (!smbox->shmem) {
200 dev_err(dev, "failed to ioremap SCMI %s shared memory\n", desc);
201 return -EADDRNOTAVAIL;
202 }
203
204 cl = &smbox->cl;
205 cl->dev = cdev;
206 cl->tx_prepare = tx ? tx_prepare : NULL;
207 cl->rx_callback = rx_callback;
208 cl->tx_block = false;
209 cl->knows_txdone = tx;
210
211 smbox->chan = mbox_request_channel(cl, tx ? 0 : p2a_chan);
212 if (IS_ERR(smbox->chan)) {
213 ret = PTR_ERR(smbox->chan);
214 if (ret != -EPROBE_DEFER)
215 dev_err(cdev,
216 "failed to request SCMI %s mailbox\n", desc);
217 return ret;
218 }
219
220 /* Additional unidirectional channel for TX if needed */
221 if (tx && a2p_rx_chan) {
222 smbox->chan_receiver = mbox_request_channel(cl, a2p_rx_chan);
223 if (IS_ERR(smbox->chan_receiver)) {
224 ret = PTR_ERR(smbox->chan_receiver);
225 if (ret != -EPROBE_DEFER)
226 dev_err(cdev, "failed to request SCMI Tx Receiver mailbox\n");
227 return ret;
228 }
229 }
230
231 cinfo->transport_info = smbox;
232 smbox->cinfo = cinfo;
233 mutex_init(&smbox->chan_lock);
234
235 return 0;
236 }
237
mailbox_chan_free(int id,void * p,void * data)238 static int mailbox_chan_free(int id, void *p, void *data)
239 {
240 struct scmi_chan_info *cinfo = p;
241 struct scmi_mailbox *smbox = cinfo->transport_info;
242
243 if (smbox && !IS_ERR(smbox->chan)) {
244 mbox_free_channel(smbox->chan);
245 mbox_free_channel(smbox->chan_receiver);
246 cinfo->transport_info = NULL;
247 smbox->chan = NULL;
248 smbox->chan_receiver = NULL;
249 smbox->cinfo = NULL;
250 }
251
252 return 0;
253 }
254
mailbox_send_message(struct scmi_chan_info * cinfo,struct scmi_xfer * xfer)255 static int mailbox_send_message(struct scmi_chan_info *cinfo,
256 struct scmi_xfer *xfer)
257 {
258 struct scmi_mailbox *smbox = cinfo->transport_info;
259 int ret;
260
261 /*
262 * The mailbox layer has its own queue. However the mailbox queue
263 * confuses the per message SCMI timeouts since the clock starts when
264 * the message is submitted into the mailbox queue. So when multiple
265 * messages are queued up the clock starts on all messages instead of
266 * only the one inflight.
267 */
268 mutex_lock(&smbox->chan_lock);
269
270 ret = mbox_send_message(smbox->chan, xfer);
271 /* mbox_send_message returns non-negative value on success */
272 if (ret < 0) {
273 mutex_unlock(&smbox->chan_lock);
274 return ret;
275 }
276
277 return 0;
278 }
279
mailbox_mark_txdone(struct scmi_chan_info * cinfo,int ret,struct scmi_xfer * __unused)280 static void mailbox_mark_txdone(struct scmi_chan_info *cinfo, int ret,
281 struct scmi_xfer *__unused)
282 {
283 struct scmi_mailbox *smbox = cinfo->transport_info;
284
285 mbox_client_txdone(smbox->chan, ret);
286
287 /* Release channel */
288 mutex_unlock(&smbox->chan_lock);
289 }
290
mailbox_fetch_response(struct scmi_chan_info * cinfo,struct scmi_xfer * xfer)291 static void mailbox_fetch_response(struct scmi_chan_info *cinfo,
292 struct scmi_xfer *xfer)
293 {
294 struct scmi_mailbox *smbox = cinfo->transport_info;
295
296 shmem_fetch_response(smbox->shmem, xfer);
297 }
298
mailbox_fetch_notification(struct scmi_chan_info * cinfo,size_t max_len,struct scmi_xfer * xfer)299 static void mailbox_fetch_notification(struct scmi_chan_info *cinfo,
300 size_t max_len, struct scmi_xfer *xfer)
301 {
302 struct scmi_mailbox *smbox = cinfo->transport_info;
303
304 shmem_fetch_notification(smbox->shmem, max_len, xfer);
305 }
306
mailbox_clear_channel(struct scmi_chan_info * cinfo)307 static void mailbox_clear_channel(struct scmi_chan_info *cinfo)
308 {
309 struct scmi_mailbox *smbox = cinfo->transport_info;
310
311 shmem_clear_channel(smbox->shmem);
312 }
313
314 static bool
mailbox_poll_done(struct scmi_chan_info * cinfo,struct scmi_xfer * xfer)315 mailbox_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
316 {
317 struct scmi_mailbox *smbox = cinfo->transport_info;
318
319 return shmem_poll_done(smbox->shmem, xfer);
320 }
321
322 static const struct scmi_transport_ops scmi_mailbox_ops = {
323 .chan_available = mailbox_chan_available,
324 .chan_setup = mailbox_chan_setup,
325 .chan_free = mailbox_chan_free,
326 .send_message = mailbox_send_message,
327 .mark_txdone = mailbox_mark_txdone,
328 .fetch_response = mailbox_fetch_response,
329 .fetch_notification = mailbox_fetch_notification,
330 .clear_channel = mailbox_clear_channel,
331 .poll_done = mailbox_poll_done,
332 };
333
334 const struct scmi_desc scmi_mailbox_desc = {
335 .ops = &scmi_mailbox_ops,
336 .max_rx_timeout_ms = 30, /* We may increase this if required */
337 .max_msg = 20, /* Limited by MBOX_TX_QUEUE_LEN */
338 .max_msg_size = 128,
339 };
340