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a17d94f0 SG |
1 | /* |
2 | * ChromeOS EC multi-function device (SPI) | |
3 | * | |
4 | * Copyright (C) 2012 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 | #include <linux/delay.h> | |
17 | #include <linux/kernel.h> | |
18 | #include <linux/module.h> | |
19 | #include <linux/mfd/cros_ec.h> | |
20 | #include <linux/mfd/cros_ec_commands.h> | |
01e73c89 | 21 | #include <linux/of.h> |
a17d94f0 SG |
22 | #include <linux/platform_device.h> |
23 | #include <linux/slab.h> | |
24 | #include <linux/spi/spi.h> | |
25 | ||
26 | ||
27 | /* The header byte, which follows the preamble */ | |
28 | #define EC_MSG_HEADER 0xec | |
29 | ||
30 | /* | |
31 | * Number of EC preamble bytes we read at a time. Since it takes | |
32 | * about 400-500us for the EC to respond there is not a lot of | |
33 | * point in tuning this. If the EC could respond faster then | |
34 | * we could increase this so that might expect the preamble and | |
35 | * message to occur in a single transaction. However, the maximum | |
36 | * SPI transfer size is 256 bytes, so at 5MHz we need a response | |
37 | * time of perhaps <320us (200 bytes / 1600 bits). | |
38 | */ | |
39 | #define EC_MSG_PREAMBLE_COUNT 32 | |
40 | ||
41 | /* | |
42 | * We must get a response from the EC in 5ms. This is a very long | |
43 | * time, but the flash write command can take 2-3ms. The EC command | |
44 | * processing is currently not very fast (about 500us). We could | |
45 | * look at speeding this up and making the flash write command a | |
46 | * 'slow' command, requiring a GET_STATUS wait loop, like flash | |
47 | * erase. | |
48 | */ | |
49 | #define EC_MSG_DEADLINE_MS 5 | |
50 | ||
51 | /* | |
52 | * Time between raising the SPI chip select (for the end of a | |
53 | * transaction) and dropping it again (for the next transaction). | |
49f91ac3 DB |
54 | * If we go too fast, the EC will miss the transaction. We know that we |
55 | * need at least 70 us with the 16 MHz STM32 EC, so go with 200 us to be | |
56 | * safe. | |
a17d94f0 | 57 | */ |
49f91ac3 | 58 | #define EC_SPI_RECOVERY_TIME_NS (200 * 1000) |
a17d94f0 SG |
59 | |
60 | /** | |
61 | * struct cros_ec_spi - information about a SPI-connected EC | |
62 | * | |
63 | * @spi: SPI device we are connected to | |
64 | * @last_transfer_ns: time that we last finished a transfer, or 0 if there | |
65 | * if no record | |
01e73c89 RK |
66 | * @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that |
67 | * is sent when we want to turn off CS at the end of a transaction. | |
a17d94f0 SG |
68 | */ |
69 | struct cros_ec_spi { | |
70 | struct spi_device *spi; | |
71 | s64 last_transfer_ns; | |
01e73c89 | 72 | unsigned int end_of_msg_delay; |
a17d94f0 SG |
73 | }; |
74 | ||
75 | static void debug_packet(struct device *dev, const char *name, u8 *ptr, | |
76 | int len) | |
77 | { | |
78 | #ifdef DEBUG | |
79 | int i; | |
80 | ||
81 | dev_dbg(dev, "%s: ", name); | |
82 | for (i = 0; i < len; i++) | |
9e146f43 TR |
83 | pr_cont(" %02x", ptr[i]); |
84 | ||
85 | pr_cont("\n"); | |
a17d94f0 SG |
86 | #endif |
87 | } | |
88 | ||
89 | /** | |
90 | * cros_ec_spi_receive_response - Receive a response from the EC. | |
91 | * | |
92 | * This function has two phases: reading the preamble bytes (since if we read | |
93 | * data from the EC before it is ready to send, we just get preamble) and | |
94 | * reading the actual message. | |
95 | * | |
96 | * The received data is placed into ec_dev->din. | |
97 | * | |
98 | * @ec_dev: ChromeOS EC device | |
99 | * @need_len: Number of message bytes we need to read | |
100 | */ | |
101 | static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev, | |
102 | int need_len) | |
103 | { | |
104 | struct cros_ec_spi *ec_spi = ec_dev->priv; | |
105 | struct spi_transfer trans; | |
106 | struct spi_message msg; | |
107 | u8 *ptr, *end; | |
108 | int ret; | |
109 | unsigned long deadline; | |
110 | int todo; | |
111 | ||
112 | /* Receive data until we see the header byte */ | |
113 | deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS); | |
114 | do { | |
daf93d22 | 115 | memset(&trans, 0, sizeof(trans)); |
a17d94f0 SG |
116 | trans.cs_change = 1; |
117 | trans.rx_buf = ptr = ec_dev->din; | |
118 | trans.len = EC_MSG_PREAMBLE_COUNT; | |
119 | ||
120 | spi_message_init(&msg); | |
121 | spi_message_add_tail(&trans, &msg); | |
122 | ret = spi_sync(ec_spi->spi, &msg); | |
123 | if (ret < 0) { | |
124 | dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); | |
125 | return ret; | |
126 | } | |
127 | ||
128 | for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) { | |
129 | if (*ptr == EC_MSG_HEADER) { | |
c34924b9 | 130 | dev_dbg(ec_dev->dev, "msg found at %zd\n", |
a17d94f0 SG |
131 | ptr - ec_dev->din); |
132 | break; | |
133 | } | |
134 | } | |
135 | ||
136 | if (time_after(jiffies, deadline)) { | |
137 | dev_warn(ec_dev->dev, "EC failed to respond in time\n"); | |
138 | return -ETIMEDOUT; | |
139 | } | |
140 | } while (ptr == end); | |
141 | ||
142 | /* | |
143 | * ptr now points to the header byte. Copy any valid data to the | |
144 | * start of our buffer | |
145 | */ | |
146 | todo = end - ++ptr; | |
147 | BUG_ON(todo < 0 || todo > ec_dev->din_size); | |
148 | todo = min(todo, need_len); | |
149 | memmove(ec_dev->din, ptr, todo); | |
150 | ptr = ec_dev->din + todo; | |
151 | dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n", | |
152 | need_len, todo); | |
153 | need_len -= todo; | |
154 | ||
155 | /* Receive data until we have it all */ | |
156 | while (need_len > 0) { | |
157 | /* | |
158 | * We can't support transfers larger than the SPI FIFO size | |
159 | * unless we have DMA. We don't have DMA on the ISP SPI ports | |
160 | * for Exynos. We need a way of asking SPI driver for | |
161 | * maximum-supported transfer size. | |
162 | */ | |
163 | todo = min(need_len, 256); | |
c34924b9 | 164 | dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n", |
a17d94f0 SG |
165 | todo, need_len, ptr - ec_dev->din); |
166 | ||
daf93d22 | 167 | memset(&trans, 0, sizeof(trans)); |
a17d94f0 SG |
168 | trans.cs_change = 1; |
169 | trans.rx_buf = ptr; | |
170 | trans.len = todo; | |
171 | spi_message_init(&msg); | |
172 | spi_message_add_tail(&trans, &msg); | |
173 | ||
174 | /* send command to EC and read answer */ | |
175 | BUG_ON((u8 *)trans.rx_buf - ec_dev->din + todo > | |
176 | ec_dev->din_size); | |
177 | ret = spi_sync(ec_spi->spi, &msg); | |
178 | if (ret < 0) { | |
179 | dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); | |
180 | return ret; | |
181 | } | |
182 | ||
183 | debug_packet(ec_dev->dev, "interim", ptr, todo); | |
184 | ptr += todo; | |
185 | need_len -= todo; | |
186 | } | |
187 | ||
c34924b9 | 188 | dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din); |
a17d94f0 SG |
189 | |
190 | return 0; | |
191 | } | |
192 | ||
193 | /** | |
194 | * cros_ec_command_spi_xfer - Transfer a message over SPI and receive the reply | |
195 | * | |
196 | * @ec_dev: ChromeOS EC device | |
197 | * @ec_msg: Message to transfer | |
198 | */ | |
199 | static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev, | |
200 | struct cros_ec_msg *ec_msg) | |
201 | { | |
202 | struct cros_ec_spi *ec_spi = ec_dev->priv; | |
203 | struct spi_transfer trans; | |
204 | struct spi_message msg; | |
205 | int i, len; | |
206 | u8 *ptr; | |
207 | int sum; | |
208 | int ret = 0, final_ret; | |
209 | struct timespec ts; | |
210 | ||
211 | len = cros_ec_prepare_tx(ec_dev, ec_msg); | |
212 | dev_dbg(ec_dev->dev, "prepared, len=%d\n", len); | |
213 | ||
214 | /* If it's too soon to do another transaction, wait */ | |
215 | if (ec_spi->last_transfer_ns) { | |
216 | struct timespec ts; | |
217 | unsigned long delay; /* The delay completed so far */ | |
218 | ||
219 | ktime_get_ts(&ts); | |
220 | delay = timespec_to_ns(&ts) - ec_spi->last_transfer_ns; | |
221 | if (delay < EC_SPI_RECOVERY_TIME_NS) | |
222 | ndelay(delay); | |
223 | } | |
224 | ||
225 | /* Transmit phase - send our message */ | |
226 | debug_packet(ec_dev->dev, "out", ec_dev->dout, len); | |
daf93d22 | 227 | memset(&trans, 0, sizeof(trans)); |
a17d94f0 SG |
228 | trans.tx_buf = ec_dev->dout; |
229 | trans.len = len; | |
230 | trans.cs_change = 1; | |
231 | spi_message_init(&msg); | |
232 | spi_message_add_tail(&trans, &msg); | |
233 | ret = spi_sync(ec_spi->spi, &msg); | |
234 | ||
235 | /* Get the response */ | |
236 | if (!ret) { | |
237 | ret = cros_ec_spi_receive_response(ec_dev, | |
238 | ec_msg->in_len + EC_MSG_TX_PROTO_BYTES); | |
239 | } else { | |
240 | dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); | |
241 | } | |
242 | ||
243 | /* turn off CS */ | |
244 | spi_message_init(&msg); | |
01e73c89 RK |
245 | |
246 | if (ec_spi->end_of_msg_delay) { | |
247 | /* | |
248 | * Add delay for last transaction, to ensure the rising edge | |
249 | * doesn't come too soon after the end of the data. | |
250 | */ | |
251 | memset(&trans, 0, sizeof(trans)); | |
252 | trans.delay_usecs = ec_spi->end_of_msg_delay; | |
253 | spi_message_add_tail(&trans, &msg); | |
254 | } | |
255 | ||
a17d94f0 SG |
256 | final_ret = spi_sync(ec_spi->spi, &msg); |
257 | ktime_get_ts(&ts); | |
258 | ec_spi->last_transfer_ns = timespec_to_ns(&ts); | |
259 | if (!ret) | |
260 | ret = final_ret; | |
261 | if (ret < 0) { | |
262 | dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); | |
263 | return ret; | |
264 | } | |
265 | ||
266 | /* check response error code */ | |
267 | ptr = ec_dev->din; | |
268 | if (ptr[0]) { | |
269 | dev_warn(ec_dev->dev, "command 0x%02x returned an error %d\n", | |
270 | ec_msg->cmd, ptr[0]); | |
271 | debug_packet(ec_dev->dev, "in_err", ptr, len); | |
272 | return -EINVAL; | |
273 | } | |
274 | len = ptr[1]; | |
275 | sum = ptr[0] + ptr[1]; | |
276 | if (len > ec_msg->in_len) { | |
277 | dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)", | |
278 | len, ec_msg->in_len); | |
279 | return -ENOSPC; | |
280 | } | |
281 | ||
282 | /* copy response packet payload and compute checksum */ | |
283 | for (i = 0; i < len; i++) { | |
284 | sum += ptr[i + 2]; | |
285 | if (ec_msg->in_len) | |
286 | ec_msg->in_buf[i] = ptr[i + 2]; | |
287 | } | |
288 | sum &= 0xff; | |
289 | ||
290 | debug_packet(ec_dev->dev, "in", ptr, len + 3); | |
291 | ||
292 | if (sum != ptr[len + 2]) { | |
293 | dev_err(ec_dev->dev, | |
294 | "bad packet checksum, expected %02x, got %02x\n", | |
295 | sum, ptr[len + 2]); | |
296 | return -EBADMSG; | |
297 | } | |
298 | ||
299 | return 0; | |
300 | } | |
301 | ||
01e73c89 RK |
302 | static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev) |
303 | { | |
304 | struct device_node *np = dev->of_node; | |
305 | u32 val; | |
306 | int ret; | |
307 | ||
308 | ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val); | |
309 | if (!ret) | |
310 | ec_spi->end_of_msg_delay = val; | |
311 | } | |
312 | ||
9922b412 | 313 | static int cros_ec_spi_probe(struct spi_device *spi) |
a17d94f0 SG |
314 | { |
315 | struct device *dev = &spi->dev; | |
316 | struct cros_ec_device *ec_dev; | |
317 | struct cros_ec_spi *ec_spi; | |
318 | int err; | |
319 | ||
320 | spi->bits_per_word = 8; | |
321 | spi->mode = SPI_MODE_0; | |
322 | err = spi_setup(spi); | |
323 | if (err < 0) | |
324 | return err; | |
325 | ||
326 | ec_spi = devm_kzalloc(dev, sizeof(*ec_spi), GFP_KERNEL); | |
327 | if (ec_spi == NULL) | |
328 | return -ENOMEM; | |
329 | ec_spi->spi = spi; | |
330 | ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL); | |
331 | if (!ec_dev) | |
332 | return -ENOMEM; | |
333 | ||
01e73c89 RK |
334 | /* Check for any DT properties */ |
335 | cros_ec_spi_dt_probe(ec_spi, dev); | |
336 | ||
a17d94f0 SG |
337 | spi_set_drvdata(spi, ec_dev); |
338 | ec_dev->name = "SPI"; | |
339 | ec_dev->dev = dev; | |
340 | ec_dev->priv = ec_spi; | |
341 | ec_dev->irq = spi->irq; | |
342 | ec_dev->command_xfer = cros_ec_command_spi_xfer; | |
343 | ec_dev->ec_name = ec_spi->spi->modalias; | |
344 | ec_dev->phys_name = dev_name(&ec_spi->spi->dev); | |
345 | ec_dev->parent = &ec_spi->spi->dev; | |
346 | ec_dev->din_size = EC_MSG_BYTES + EC_MSG_PREAMBLE_COUNT; | |
347 | ec_dev->dout_size = EC_MSG_BYTES; | |
348 | ||
349 | err = cros_ec_register(ec_dev); | |
350 | if (err) { | |
351 | dev_err(dev, "cannot register EC\n"); | |
352 | return err; | |
353 | } | |
354 | ||
355 | return 0; | |
356 | } | |
357 | ||
9922b412 | 358 | static int cros_ec_spi_remove(struct spi_device *spi) |
a17d94f0 SG |
359 | { |
360 | struct cros_ec_device *ec_dev; | |
361 | ||
362 | ec_dev = spi_get_drvdata(spi); | |
363 | cros_ec_remove(ec_dev); | |
364 | ||
365 | return 0; | |
366 | } | |
367 | ||
368 | #ifdef CONFIG_PM_SLEEP | |
369 | static int cros_ec_spi_suspend(struct device *dev) | |
370 | { | |
371 | struct cros_ec_device *ec_dev = dev_get_drvdata(dev); | |
372 | ||
373 | return cros_ec_suspend(ec_dev); | |
374 | } | |
375 | ||
376 | static int cros_ec_spi_resume(struct device *dev) | |
377 | { | |
378 | struct cros_ec_device *ec_dev = dev_get_drvdata(dev); | |
379 | ||
380 | return cros_ec_resume(ec_dev); | |
381 | } | |
382 | #endif | |
383 | ||
384 | static SIMPLE_DEV_PM_OPS(cros_ec_spi_pm_ops, cros_ec_spi_suspend, | |
385 | cros_ec_spi_resume); | |
386 | ||
387 | static const struct spi_device_id cros_ec_spi_id[] = { | |
388 | { "cros-ec-spi", 0 }, | |
389 | { } | |
390 | }; | |
391 | MODULE_DEVICE_TABLE(spi, cros_ec_spi_id); | |
392 | ||
393 | static struct spi_driver cros_ec_driver_spi = { | |
394 | .driver = { | |
395 | .name = "cros-ec-spi", | |
396 | .owner = THIS_MODULE, | |
397 | .pm = &cros_ec_spi_pm_ops, | |
398 | }, | |
9922b412 TR |
399 | .probe = cros_ec_spi_probe, |
400 | .remove = cros_ec_spi_remove, | |
a17d94f0 SG |
401 | .id_table = cros_ec_spi_id, |
402 | }; | |
403 | ||
404 | module_spi_driver(cros_ec_driver_spi); | |
405 | ||
ea0f8b0b | 406 | MODULE_LICENSE("GPL v2"); |
a17d94f0 | 407 | MODULE_DESCRIPTION("ChromeOS EC multi function device (SPI)"); |