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  */
27 struct 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 
37 static 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 
44 static 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 
65 static 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  */
98 static 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 
159 static 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 
235 static 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 
252 static 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 
267 static 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 
281 static 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 
289 static 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 
297 static 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 
304 static bool
305 mailbox_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 
312 static 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 
324 const 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