blob: 84af8d7a429544e7369daf66d2dbedb578cb12a1 [file] [log] [blame]
Simon Glassa17d94f2013-02-25 14:08:39 -08001/*
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>
Rhyland Klein01e73c82013-12-09 12:36:09 +010021#include <linux/of.h>
Simon Glassa17d94f2013-02-25 14:08:39 -080022#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).
Derek Basehore49f91ac2013-11-18 11:30:48 +010054 * 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.
Simon Glassa17d94f2013-02-25 14:08:39 -080057 */
Derek Basehore49f91ac2013-11-18 11:30:48 +010058#define EC_SPI_RECOVERY_TIME_NS (200 * 1000)
Simon Glassa17d94f2013-02-25 14:08:39 -080059
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
Rhyland Klein01e73c82013-12-09 12:36:09 +010066 * @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.
Simon Glassa17d94f2013-02-25 14:08:39 -080068 */
69struct cros_ec_spi {
70 struct spi_device *spi;
71 s64 last_transfer_ns;
Rhyland Klein01e73c82013-12-09 12:36:09 +010072 unsigned int end_of_msg_delay;
Simon Glassa17d94f2013-02-25 14:08:39 -080073};
74
75static 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++)
Thierry Reding9e146f42013-11-18 11:30:49 +010083 pr_cont(" %02x", ptr[i]);
84
85 pr_cont("\n");
Simon Glassa17d94f2013-02-25 14:08:39 -080086#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 */
101static 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 {
Thierry Redingdaf93d22013-12-09 12:36:10 +0100115 memset(&trans, 0, sizeof(trans));
Simon Glassa17d94f2013-02-25 14:08:39 -0800116 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) {
Geert Uytterhoevenc34924b2013-05-08 23:37:45 +0200130 dev_dbg(ec_dev->dev, "msg found at %zd\n",
Simon Glassa17d94f2013-02-25 14:08:39 -0800131 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);
Geert Uytterhoevenc34924b2013-05-08 23:37:45 +0200164 dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
Simon Glassa17d94f2013-02-25 14:08:39 -0800165 todo, need_len, ptr - ec_dev->din);
166
Thierry Redingdaf93d22013-12-09 12:36:10 +0100167 memset(&trans, 0, sizeof(trans));
Simon Glassa17d94f2013-02-25 14:08:39 -0800168 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
Geert Uytterhoevenc34924b2013-05-08 23:37:45 +0200188 dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);
Simon Glassa17d94f2013-02-25 14:08:39 -0800189
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 */
199static 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);
Thierry Redingdaf93d22013-12-09 12:36:10 +0100227 memset(&trans, 0, sizeof(trans));
Simon Glassa17d94f2013-02-25 14:08:39 -0800228 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);
Rhyland Klein01e73c82013-12-09 12:36:09 +0100245
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
Simon Glassa17d94f2013-02-25 14:08:39 -0800256 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
Rhyland Klein01e73c82013-12-09 12:36:09 +0100302static 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
Thierry Reding9922b412013-11-25 13:22:30 +0100313static int cros_ec_spi_probe(struct spi_device *spi)
Simon Glassa17d94f2013-02-25 14:08:39 -0800314{
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
Rhyland Klein01e73c82013-12-09 12:36:09 +0100334 /* Check for any DT properties */
335 cros_ec_spi_dt_probe(ec_spi, dev);
336
Simon Glassa17d94f2013-02-25 14:08:39 -0800337 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
Thierry Reding9922b412013-11-25 13:22:30 +0100358static int cros_ec_spi_remove(struct spi_device *spi)
Simon Glassa17d94f2013-02-25 14:08:39 -0800359{
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
369static 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
376static 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
384static SIMPLE_DEV_PM_OPS(cros_ec_spi_pm_ops, cros_ec_spi_suspend,
385 cros_ec_spi_resume);
386
387static const struct spi_device_id cros_ec_spi_id[] = {
388 { "cros-ec-spi", 0 },
389 { }
390};
391MODULE_DEVICE_TABLE(spi, cros_ec_spi_id);
392
393static 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 },
Thierry Reding9922b412013-11-25 13:22:30 +0100399 .probe = cros_ec_spi_probe,
400 .remove = cros_ec_spi_remove,
Simon Glassa17d94f2013-02-25 14:08:39 -0800401 .id_table = cros_ec_spi_id,
402};
403
404module_spi_driver(cros_ec_driver_spi);
405
Thierry Redingea0f8b02013-12-09 11:05:38 +0100406MODULE_LICENSE("GPL v2");
Simon Glassa17d94f2013-02-25 14:08:39 -0800407MODULE_DESCRIPTION("ChromeOS EC multi function device (SPI)");