blob: 063e89eff791a7de06ec2abfa5f814d9ab0193ee [file] [log] [blame]
Gwendal Grignou11b86c72017-10-12 19:33:23 +02001/*
2 * Driver for older Chrome OS EC accelerometer
3 *
4 * Copyright 2017 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 * This driver uses the memory mapper cros-ec interface to communicate
16 * with the Chrome OS EC about accelerometer data.
17 * Accelerometer access is presented through iio sysfs.
18 */
19
20#include <linux/delay.h>
21#include <linux/device.h>
22#include <linux/iio/buffer.h>
23#include <linux/iio/iio.h>
24#include <linux/iio/kfifo_buf.h>
25#include <linux/iio/trigger_consumer.h>
26#include <linux/iio/triggered_buffer.h>
27#include <linux/kernel.h>
28#include <linux/mfd/cros_ec.h>
29#include <linux/mfd/cros_ec_commands.h>
30#include <linux/module.h>
31#include <linux/slab.h>
32#include <linux/sysfs.h>
33#include <linux/platform_device.h>
34
35#define DRV_NAME "cros-ec-accel-legacy"
36
37/*
38 * Sensor scale hard coded at 10 bits per g, computed as:
39 * g / (2^10 - 1) = 0.009586168; with g = 9.80665 m.s^-2
40 */
41#define ACCEL_LEGACY_NSCALE 9586168
42
43/* Indices for EC sensor values. */
44enum {
45 X,
46 Y,
47 Z,
48 MAX_AXIS,
49};
50
51/* State data for cros_ec_accel_legacy iio driver. */
52struct cros_ec_accel_legacy_state {
53 struct cros_ec_device *ec;
54
55 /*
56 * Array holding data from a single capture. 2 bytes per channel
57 * for the 3 channels plus the timestamp which is always last and
58 * 8-bytes aligned.
59 */
60 s16 capture_data[8];
61 s8 sign[MAX_AXIS];
62 u8 sensor_num;
63};
64
65static int ec_cmd_read_u8(struct cros_ec_device *ec, unsigned int offset,
66 u8 *dest)
67{
68 return ec->cmd_readmem(ec, offset, 1, dest);
69}
70
71static int ec_cmd_read_u16(struct cros_ec_device *ec, unsigned int offset,
72 u16 *dest)
73{
74 __le16 tmp;
75 int ret = ec->cmd_readmem(ec, offset, 2, &tmp);
76
77 *dest = le16_to_cpu(tmp);
78
79 return ret;
80}
81
82/**
83 * read_ec_until_not_busy() - Read from EC status byte until it reads not busy.
84 * @st: Pointer to state information for device.
85 *
86 * This function reads EC status until its busy bit gets cleared. It does not
87 * wait indefinitely and returns -EIO if the EC status is still busy after a
88 * few hundreds milliseconds.
89 *
90 * Return: 8-bit status if ok, -EIO on error
91 */
92static int read_ec_until_not_busy(struct cros_ec_accel_legacy_state *st)
93{
94 struct cros_ec_device *ec = st->ec;
95 u8 status;
96 int attempts = 0;
97
98 ec_cmd_read_u8(ec, EC_MEMMAP_ACC_STATUS, &status);
99 while (status & EC_MEMMAP_ACC_STATUS_BUSY_BIT) {
100 /* Give up after enough attempts, return error. */
101 if (attempts++ >= 50)
102 return -EIO;
103
104 /* Small delay every so often. */
105 if (attempts % 5 == 0)
106 msleep(25);
107
108 ec_cmd_read_u8(ec, EC_MEMMAP_ACC_STATUS, &status);
109 }
110
111 return status;
112}
113
114/**
115 * read_ec_accel_data_unsafe() - Read acceleration data from EC shared memory.
116 * @st: Pointer to state information for device.
117 * @scan_mask: Bitmap of the sensor indices to scan.
118 * @data: Location to store data.
119 *
120 * This is the unsafe function for reading the EC data. It does not guarantee
121 * that the EC will not modify the data as it is being read in.
122 */
123static void read_ec_accel_data_unsafe(struct cros_ec_accel_legacy_state *st,
124 unsigned long scan_mask, s16 *data)
125{
126 int i = 0;
127 int num_enabled = bitmap_weight(&scan_mask, MAX_AXIS);
128
129 /* Read all sensors enabled in scan_mask. Each value is 2 bytes. */
130 while (num_enabled--) {
131 i = find_next_bit(&scan_mask, MAX_AXIS, i);
132 ec_cmd_read_u16(st->ec,
133 EC_MEMMAP_ACC_DATA +
134 sizeof(s16) *
135 (1 + i + st->sensor_num * MAX_AXIS),
136 data);
137 *data *= st->sign[i];
138 i++;
139 data++;
140 }
141}
142
143/**
144 * read_ec_accel_data() - Read acceleration data from EC shared memory.
145 * @st: Pointer to state information for device.
146 * @scan_mask: Bitmap of the sensor indices to scan.
147 * @data: Location to store data.
148 *
149 * This is the safe function for reading the EC data. It guarantees that
150 * the data sampled was not modified by the EC while being read.
151 *
152 * Return: 0 if ok, -ve on error
153 */
154static int read_ec_accel_data(struct cros_ec_accel_legacy_state *st,
155 unsigned long scan_mask, s16 *data)
156{
157 u8 samp_id = 0xff;
158 u8 status = 0;
159 int ret;
160 int attempts = 0;
161
162 /*
163 * Continually read all data from EC until the status byte after
164 * all reads reflects that the EC is not busy and the sample id
165 * matches the sample id from before all reads. This guarantees
166 * that data read in was not modified by the EC while reading.
167 */
168 while ((status & (EC_MEMMAP_ACC_STATUS_BUSY_BIT |
169 EC_MEMMAP_ACC_STATUS_SAMPLE_ID_MASK)) != samp_id) {
170 /* If we have tried to read too many times, return error. */
171 if (attempts++ >= 5)
172 return -EIO;
173
174 /* Read status byte until EC is not busy. */
175 ret = read_ec_until_not_busy(st);
176 if (ret < 0)
177 return ret;
178 status = ret;
179
180 /*
181 * Store the current sample id so that we can compare to the
182 * sample id after reading the data.
183 */
184 samp_id = status & EC_MEMMAP_ACC_STATUS_SAMPLE_ID_MASK;
185
186 /* Read all EC data, format it, and store it into data. */
187 read_ec_accel_data_unsafe(st, scan_mask, data);
188
189 /* Read status byte. */
190 ec_cmd_read_u8(st->ec, EC_MEMMAP_ACC_STATUS, &status);
191 }
192
193 return 0;
194}
195
196static int cros_ec_accel_legacy_read(struct iio_dev *indio_dev,
197 struct iio_chan_spec const *chan,
198 int *val, int *val2, long mask)
199{
200 struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
201 s16 data = 0;
202 int ret = IIO_VAL_INT;
203
204 switch (mask) {
205 case IIO_CHAN_INFO_RAW:
206 ret = read_ec_accel_data(st, (1 << chan->scan_index), &data);
207 if (ret)
208 return ret;
209 *val = data;
210 return IIO_VAL_INT;
211 case IIO_CHAN_INFO_SCALE:
212 *val = 0;
213 *val2 = ACCEL_LEGACY_NSCALE;
214 return IIO_VAL_INT_PLUS_NANO;
215 case IIO_CHAN_INFO_CALIBBIAS:
216 /* Calibration not supported. */
217 *val = 0;
218 return IIO_VAL_INT;
219 default:
220 return -EINVAL;
221 }
222}
223
224static int cros_ec_accel_legacy_write(struct iio_dev *indio_dev,
225 struct iio_chan_spec const *chan,
226 int val, int val2, long mask)
227{
228 /*
229 * Do nothing but don't return an error code to allow calibration
230 * script to work.
231 */
232 if (mask == IIO_CHAN_INFO_CALIBBIAS)
233 return 0;
234
235 return -EINVAL;
236}
237
238static const struct iio_info cros_ec_accel_legacy_info = {
239 .read_raw = &cros_ec_accel_legacy_read,
240 .write_raw = &cros_ec_accel_legacy_write,
241};
242
243/**
244 * cros_ec_accel_legacy_capture() - The trigger handler function
245 * @irq: The interrupt number.
246 * @p: Private data - always a pointer to the poll func.
247 *
248 * On a trigger event occurring, if the pollfunc is attached then this
249 * handler is called as a threaded interrupt (and hence may sleep). It
250 * is responsible for grabbing data from the device and pushing it into
251 * the associated buffer.
252 *
253 * Return: IRQ_HANDLED
254 */
255static irqreturn_t cros_ec_accel_legacy_capture(int irq, void *p)
256{
257 struct iio_poll_func *pf = p;
258 struct iio_dev *indio_dev = pf->indio_dev;
259 struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
260
261 /* Clear capture data. */
262 memset(st->capture_data, 0, sizeof(st->capture_data));
263
264 /*
265 * Read data based on which channels are enabled in scan mask. Note
266 * that on a capture we are always reading the calibrated data.
267 */
268 read_ec_accel_data(st, *indio_dev->active_scan_mask, st->capture_data);
269
270 iio_push_to_buffers_with_timestamp(indio_dev, (void *)st->capture_data,
271 iio_get_time_ns(indio_dev));
272
273 /*
274 * Tell the core we are done with this trigger and ready for the
275 * next one.
276 */
277 iio_trigger_notify_done(indio_dev->trig);
278
279 return IRQ_HANDLED;
280}
281
282static char *cros_ec_accel_legacy_loc_strings[] = {
283 [MOTIONSENSE_LOC_BASE] = "base",
284 [MOTIONSENSE_LOC_LID] = "lid",
285 [MOTIONSENSE_LOC_MAX] = "unknown",
286};
287
288static ssize_t cros_ec_accel_legacy_loc(struct iio_dev *indio_dev,
289 uintptr_t private,
290 const struct iio_chan_spec *chan,
291 char *buf)
292{
293 struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
294
295 return sprintf(buf, "%s\n",
296 cros_ec_accel_legacy_loc_strings[st->sensor_num +
297 MOTIONSENSE_LOC_BASE]);
298}
299
300static ssize_t cros_ec_accel_legacy_id(struct iio_dev *indio_dev,
301 uintptr_t private,
302 const struct iio_chan_spec *chan,
303 char *buf)
304{
305 struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
306
307 return sprintf(buf, "%d\n", st->sensor_num);
308}
309
310static const struct iio_chan_spec_ext_info cros_ec_accel_legacy_ext_info[] = {
311 {
312 .name = "id",
313 .shared = IIO_SHARED_BY_ALL,
314 .read = cros_ec_accel_legacy_id,
315 },
316 {
317 .name = "location",
318 .shared = IIO_SHARED_BY_ALL,
319 .read = cros_ec_accel_legacy_loc,
320 },
321 { }
322};
323
324#define CROS_EC_ACCEL_LEGACY_CHAN(_axis) \
325 { \
326 .type = IIO_ACCEL, \
327 .channel2 = IIO_MOD_X + (_axis), \
328 .modified = 1, \
329 .info_mask_separate = \
330 BIT(IIO_CHAN_INFO_RAW) | \
331 BIT(IIO_CHAN_INFO_SCALE) | \
332 BIT(IIO_CHAN_INFO_CALIBBIAS), \
333 .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE), \
334 .ext_info = cros_ec_accel_legacy_ext_info, \
335 .scan_type = { \
336 .sign = 's', \
337 .realbits = 16, \
338 .storagebits = 16, \
339 }, \
340 } \
341
342static struct iio_chan_spec ec_accel_channels[] = {
343 CROS_EC_ACCEL_LEGACY_CHAN(X),
344 CROS_EC_ACCEL_LEGACY_CHAN(Y),
345 CROS_EC_ACCEL_LEGACY_CHAN(Z),
346 IIO_CHAN_SOFT_TIMESTAMP(MAX_AXIS)
347};
348
349static int cros_ec_accel_legacy_probe(struct platform_device *pdev)
350{
351 struct device *dev = &pdev->dev;
352 struct cros_ec_dev *ec = dev_get_drvdata(dev->parent);
353 struct cros_ec_sensor_platform *sensor_platform = dev_get_platdata(dev);
354 struct iio_dev *indio_dev;
355 struct cros_ec_accel_legacy_state *state;
356 int ret, i;
357
358 if (!ec || !ec->ec_dev) {
359 dev_warn(&pdev->dev, "No EC device found.\n");
360 return -EINVAL;
361 }
362
363 if (!ec->ec_dev->cmd_readmem) {
364 dev_warn(&pdev->dev, "EC does not support direct reads.\n");
365 return -EINVAL;
366 }
367
368 indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*state));
369 if (!indio_dev)
370 return -ENOMEM;
371
372 platform_set_drvdata(pdev, indio_dev);
373 state = iio_priv(indio_dev);
374 state->ec = ec->ec_dev;
375 state->sensor_num = sensor_platform->sensor_num;
376
377 indio_dev->dev.parent = dev;
378 indio_dev->name = pdev->name;
379 indio_dev->channels = ec_accel_channels;
380 /*
381 * Present the channel using HTML5 standard:
382 * need to invert X and Y and invert some lid axis.
383 */
384 for (i = X ; i < MAX_AXIS; i++) {
385 switch (i) {
386 case X:
387 ec_accel_channels[X].scan_index = Y;
388 case Y:
389 ec_accel_channels[Y].scan_index = X;
390 case Z:
391 ec_accel_channels[Z].scan_index = Z;
392 }
393 if (state->sensor_num == MOTIONSENSE_LOC_LID && i != Y)
394 state->sign[i] = -1;
395 else
396 state->sign[i] = 1;
397 }
398 indio_dev->num_channels = ARRAY_SIZE(ec_accel_channels);
399 indio_dev->dev.parent = &pdev->dev;
400 indio_dev->info = &cros_ec_accel_legacy_info;
401 indio_dev->modes = INDIO_DIRECT_MODE;
402
403 ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
404 cros_ec_accel_legacy_capture,
405 NULL);
406 if (ret)
407 return ret;
408
409 return devm_iio_device_register(dev, indio_dev);
410}
411
412static struct platform_driver cros_ec_accel_platform_driver = {
413 .driver = {
414 .name = DRV_NAME,
415 },
416 .probe = cros_ec_accel_legacy_probe,
417};
418module_platform_driver(cros_ec_accel_platform_driver);
419
420MODULE_DESCRIPTION("ChromeOS EC legacy accelerometer driver");
421MODULE_AUTHOR("Gwendal Grignou <gwendal@chromium.org>");
422MODULE_LICENSE("GPL");
423MODULE_ALIAS("platform:" DRV_NAME);