1 /*
2  * ChromeOS EC communication protocol helper functions
3  *
4  * Copyright (C) 2015 Google, Inc
5  *
6  * This software is licensed under the terms of the GNU General Public
7  * License version 2, as published by the Free Software Foundation, and
8  * may be copied, distributed, and modified under those terms.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  */
16 
17 #include <linux/mfd/cros_ec.h>
18 #include <linux/delay.h>
19 #include <linux/device.h>
20 #include <linux/module.h>
21 #include <linux/slab.h>
22 
23 #define EC_COMMAND_RETRIES	50
24 
25 static int prepare_packet(struct cros_ec_device *ec_dev,
26 			  struct cros_ec_command *msg)
27 {
28 	struct ec_host_request *request;
29 	u8 *out;
30 	int i;
31 	u8 csum = 0;
32 
33 	BUG_ON(ec_dev->proto_version != EC_HOST_REQUEST_VERSION);
34 	BUG_ON(msg->outsize + sizeof(*request) > ec_dev->dout_size);
35 
36 	out = ec_dev->dout;
37 	request = (struct ec_host_request *)out;
38 	request->struct_version = EC_HOST_REQUEST_VERSION;
39 	request->checksum = 0;
40 	request->command = msg->command;
41 	request->command_version = msg->version;
42 	request->reserved = 0;
43 	request->data_len = msg->outsize;
44 
45 	for (i = 0; i < sizeof(*request); i++)
46 		csum += out[i];
47 
48 	/* Copy data and update checksum */
49 	memcpy(out + sizeof(*request), msg->data, msg->outsize);
50 	for (i = 0; i < msg->outsize; i++)
51 		csum += msg->data[i];
52 
53 	request->checksum = -csum;
54 
55 	return sizeof(*request) + msg->outsize;
56 }
57 
58 static int send_command(struct cros_ec_device *ec_dev,
59 			struct cros_ec_command *msg)
60 {
61 	int ret;
62 
63 	if (ec_dev->proto_version > 2)
64 		ret = ec_dev->pkt_xfer(ec_dev, msg);
65 	else
66 		ret = ec_dev->cmd_xfer(ec_dev, msg);
67 
68 	if (msg->result == EC_RES_IN_PROGRESS) {
69 		int i;
70 		struct cros_ec_command *status_msg;
71 		struct ec_response_get_comms_status *status;
72 
73 		status_msg = kmalloc(sizeof(*status_msg) + sizeof(*status),
74 				     GFP_KERNEL);
75 		if (!status_msg)
76 			return -ENOMEM;
77 
78 		status_msg->version = 0;
79 		status_msg->command = EC_CMD_GET_COMMS_STATUS;
80 		status_msg->insize = sizeof(*status);
81 		status_msg->outsize = 0;
82 
83 		/*
84 		 * Query the EC's status until it's no longer busy or
85 		 * we encounter an error.
86 		 */
87 		for (i = 0; i < EC_COMMAND_RETRIES; i++) {
88 			usleep_range(10000, 11000);
89 
90 			ret = ec_dev->cmd_xfer(ec_dev, status_msg);
91 			if (ret < 0)
92 				break;
93 
94 			msg->result = status_msg->result;
95 			if (status_msg->result != EC_RES_SUCCESS)
96 				break;
97 
98 			status = (struct ec_response_get_comms_status *)
99 				 status_msg->data;
100 			if (!(status->flags & EC_COMMS_STATUS_PROCESSING))
101 				break;
102 		}
103 
104 		kfree(status_msg);
105 	}
106 
107 	return ret;
108 }
109 
110 int cros_ec_prepare_tx(struct cros_ec_device *ec_dev,
111 		       struct cros_ec_command *msg)
112 {
113 	u8 *out;
114 	u8 csum;
115 	int i;
116 
117 	if (ec_dev->proto_version > 2)
118 		return prepare_packet(ec_dev, msg);
119 
120 	BUG_ON(msg->outsize > EC_PROTO2_MAX_PARAM_SIZE);
121 	out = ec_dev->dout;
122 	out[0] = EC_CMD_VERSION0 + msg->version;
123 	out[1] = msg->command;
124 	out[2] = msg->outsize;
125 	csum = out[0] + out[1] + out[2];
126 	for (i = 0; i < msg->outsize; i++)
127 		csum += out[EC_MSG_TX_HEADER_BYTES + i] = msg->data[i];
128 	out[EC_MSG_TX_HEADER_BYTES + msg->outsize] = csum;
129 
130 	return EC_MSG_TX_PROTO_BYTES + msg->outsize;
131 }
132 EXPORT_SYMBOL(cros_ec_prepare_tx);
133 
134 int cros_ec_check_result(struct cros_ec_device *ec_dev,
135 			 struct cros_ec_command *msg)
136 {
137 	switch (msg->result) {
138 	case EC_RES_SUCCESS:
139 		return 0;
140 	case EC_RES_IN_PROGRESS:
141 		dev_dbg(ec_dev->dev, "command 0x%02x in progress\n",
142 			msg->command);
143 		return -EAGAIN;
144 	default:
145 		dev_dbg(ec_dev->dev, "command 0x%02x returned %d\n",
146 			msg->command, msg->result);
147 		return 0;
148 	}
149 }
150 EXPORT_SYMBOL(cros_ec_check_result);
151 
152 static int cros_ec_host_command_proto_query(struct cros_ec_device *ec_dev,
153 					    int devidx,
154 					    struct cros_ec_command *msg)
155 {
156 	/*
157 	 * Try using v3+ to query for supported protocols. If this
158 	 * command fails, fall back to v2. Returns the highest protocol
159 	 * supported by the EC.
160 	 * Also sets the max request/response/passthru size.
161 	 */
162 	int ret;
163 
164 	if (!ec_dev->pkt_xfer)
165 		return -EPROTONOSUPPORT;
166 
167 	memset(msg, 0, sizeof(*msg));
168 	msg->command = EC_CMD_PASSTHRU_OFFSET(devidx) | EC_CMD_GET_PROTOCOL_INFO;
169 	msg->insize = sizeof(struct ec_response_get_protocol_info);
170 
171 	ret = send_command(ec_dev, msg);
172 
173 	if (ret < 0) {
174 		dev_dbg(ec_dev->dev,
175 			"failed to check for EC[%d] protocol version: %d\n",
176 			devidx, ret);
177 		return ret;
178 	}
179 
180 	if (devidx > 0 && msg->result == EC_RES_INVALID_COMMAND)
181 		return -ENODEV;
182 	else if (msg->result != EC_RES_SUCCESS)
183 		return msg->result;
184 
185 	return 0;
186 }
187 
188 static int cros_ec_host_command_proto_query_v2(struct cros_ec_device *ec_dev)
189 {
190 	struct cros_ec_command *msg;
191 	struct ec_params_hello *hello_params;
192 	struct ec_response_hello *hello_response;
193 	int ret;
194 	int len = max(sizeof(*hello_params), sizeof(*hello_response));
195 
196 	msg = kmalloc(sizeof(*msg) + len, GFP_KERNEL);
197 	if (!msg)
198 		return -ENOMEM;
199 
200 	msg->version = 0;
201 	msg->command = EC_CMD_HELLO;
202 	hello_params = (struct ec_params_hello *)msg->data;
203 	msg->outsize = sizeof(*hello_params);
204 	hello_response = (struct ec_response_hello *)msg->data;
205 	msg->insize = sizeof(*hello_response);
206 
207 	hello_params->in_data = 0xa0b0c0d0;
208 
209 	ret = send_command(ec_dev, msg);
210 
211 	if (ret < 0) {
212 		dev_dbg(ec_dev->dev,
213 			"EC failed to respond to v2 hello: %d\n",
214 			ret);
215 		goto exit;
216 	} else if (msg->result != EC_RES_SUCCESS) {
217 		dev_err(ec_dev->dev,
218 			"EC responded to v2 hello with error: %d\n",
219 			msg->result);
220 		ret = msg->result;
221 		goto exit;
222 	} else if (hello_response->out_data != 0xa1b2c3d4) {
223 		dev_err(ec_dev->dev,
224 			"EC responded to v2 hello with bad result: %u\n",
225 			hello_response->out_data);
226 		ret = -EBADMSG;
227 		goto exit;
228 	}
229 
230 	ret = 0;
231 
232  exit:
233 	kfree(msg);
234 	return ret;
235 }
236 
237 int cros_ec_query_all(struct cros_ec_device *ec_dev)
238 {
239 	struct device *dev = ec_dev->dev;
240 	struct cros_ec_command *proto_msg;
241 	struct ec_response_get_protocol_info *proto_info;
242 	int ret;
243 
244 	proto_msg = kzalloc(sizeof(*proto_msg) + sizeof(*proto_info),
245 			    GFP_KERNEL);
246 	if (!proto_msg)
247 		return -ENOMEM;
248 
249 	/* First try sending with proto v3. */
250 	ec_dev->proto_version = 3;
251 	ret = cros_ec_host_command_proto_query(ec_dev, 0, proto_msg);
252 
253 	if (ret == 0) {
254 		proto_info = (struct ec_response_get_protocol_info *)
255 			proto_msg->data;
256 		ec_dev->max_request = proto_info->max_request_packet_size -
257 			sizeof(struct ec_host_request);
258 		ec_dev->max_response = proto_info->max_response_packet_size -
259 			sizeof(struct ec_host_response);
260 		ec_dev->proto_version =
261 			min(EC_HOST_REQUEST_VERSION,
262 					fls(proto_info->protocol_versions) - 1);
263 		dev_dbg(ec_dev->dev,
264 			"using proto v%u\n",
265 			ec_dev->proto_version);
266 
267 		ec_dev->din_size = ec_dev->max_response +
268 			sizeof(struct ec_host_response) +
269 			EC_MAX_RESPONSE_OVERHEAD;
270 		ec_dev->dout_size = ec_dev->max_request +
271 			sizeof(struct ec_host_request) +
272 			EC_MAX_REQUEST_OVERHEAD;
273 
274 		/*
275 		 * Check for PD
276 		 */
277 		ret = cros_ec_host_command_proto_query(ec_dev, 1, proto_msg);
278 
279 		if (ret) {
280 			dev_dbg(ec_dev->dev, "no PD chip found: %d\n", ret);
281 			ec_dev->max_passthru = 0;
282 		} else {
283 			dev_dbg(ec_dev->dev, "found PD chip\n");
284 			ec_dev->max_passthru =
285 				proto_info->max_request_packet_size -
286 				sizeof(struct ec_host_request);
287 		}
288 	} else {
289 		/* Try querying with a v2 hello message. */
290 		ec_dev->proto_version = 2;
291 		ret = cros_ec_host_command_proto_query_v2(ec_dev);
292 
293 		if (ret == 0) {
294 			/* V2 hello succeeded. */
295 			dev_dbg(ec_dev->dev, "falling back to proto v2\n");
296 
297 			ec_dev->max_request = EC_PROTO2_MAX_PARAM_SIZE;
298 			ec_dev->max_response = EC_PROTO2_MAX_PARAM_SIZE;
299 			ec_dev->max_passthru = 0;
300 			ec_dev->pkt_xfer = NULL;
301 			ec_dev->din_size = EC_PROTO2_MSG_BYTES;
302 			ec_dev->dout_size = EC_PROTO2_MSG_BYTES;
303 		} else {
304 			/*
305 			 * It's possible for a test to occur too early when
306 			 * the EC isn't listening. If this happens, we'll
307 			 * test later when the first command is run.
308 			 */
309 			ec_dev->proto_version = EC_PROTO_VERSION_UNKNOWN;
310 			dev_dbg(ec_dev->dev, "EC query failed: %d\n", ret);
311 			goto exit;
312 		}
313 	}
314 
315 	devm_kfree(dev, ec_dev->din);
316 	devm_kfree(dev, ec_dev->dout);
317 
318 	ec_dev->din = devm_kzalloc(dev, ec_dev->din_size, GFP_KERNEL);
319 	if (!ec_dev->din) {
320 		ret = -ENOMEM;
321 		goto exit;
322 	}
323 
324 	ec_dev->dout = devm_kzalloc(dev, ec_dev->dout_size, GFP_KERNEL);
325 	if (!ec_dev->dout) {
326 		devm_kfree(dev, ec_dev->din);
327 		ret = -ENOMEM;
328 		goto exit;
329 	}
330 
331 exit:
332 	kfree(proto_msg);
333 	return ret;
334 }
335 EXPORT_SYMBOL(cros_ec_query_all);
336 
337 int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
338 		     struct cros_ec_command *msg)
339 {
340 	int ret;
341 
342 	mutex_lock(&ec_dev->lock);
343 	if (ec_dev->proto_version == EC_PROTO_VERSION_UNKNOWN) {
344 		ret = cros_ec_query_all(ec_dev);
345 		if (ret) {
346 			dev_err(ec_dev->dev,
347 				"EC version unknown and query failed; aborting command\n");
348 			mutex_unlock(&ec_dev->lock);
349 			return ret;
350 		}
351 	}
352 
353 	if (msg->insize > ec_dev->max_response) {
354 		dev_dbg(ec_dev->dev, "clamping message receive buffer\n");
355 		msg->insize = ec_dev->max_response;
356 	}
357 
358 	if (msg->command < EC_CMD_PASSTHRU_OFFSET(1)) {
359 		if (msg->outsize > ec_dev->max_request) {
360 			dev_err(ec_dev->dev,
361 				"request of size %u is too big (max: %u)\n",
362 				msg->outsize,
363 				ec_dev->max_request);
364 			mutex_unlock(&ec_dev->lock);
365 			return -EMSGSIZE;
366 		}
367 	} else {
368 		if (msg->outsize > ec_dev->max_passthru) {
369 			dev_err(ec_dev->dev,
370 				"passthru rq of size %u is too big (max: %u)\n",
371 				msg->outsize,
372 				ec_dev->max_passthru);
373 			mutex_unlock(&ec_dev->lock);
374 			return -EMSGSIZE;
375 		}
376 	}
377 	ret = send_command(ec_dev, msg);
378 	mutex_unlock(&ec_dev->lock);
379 
380 	return ret;
381 }
382 EXPORT_SYMBOL(cros_ec_cmd_xfer);
383