Gwendal Grignou | 11b86c7 | 2017-10-12 19:33:23 +0200 | [diff] [blame] | 1 | /* |
| 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. */ |
| 44 | enum { |
| 45 | X, |
| 46 | Y, |
| 47 | Z, |
| 48 | MAX_AXIS, |
| 49 | }; |
| 50 | |
| 51 | /* State data for cros_ec_accel_legacy iio driver. */ |
| 52 | struct 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 | |
| 65 | static 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 | |
| 71 | static 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 | */ |
| 92 | static 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 | */ |
| 123 | static 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 | */ |
| 154 | static 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 | |
| 196 | static 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 | |
| 224 | static 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 | |
| 238 | static 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 | */ |
| 255 | static 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 | |
| 282 | static char *cros_ec_accel_legacy_loc_strings[] = { |
| 283 | [MOTIONSENSE_LOC_BASE] = "base", |
| 284 | [MOTIONSENSE_LOC_LID] = "lid", |
| 285 | [MOTIONSENSE_LOC_MAX] = "unknown", |
| 286 | }; |
| 287 | |
| 288 | static 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 | |
| 300 | static 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 | |
| 310 | static 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 | |
| 342 | static 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 | |
| 349 | static 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 | |
| 412 | static struct platform_driver cros_ec_accel_platform_driver = { |
| 413 | .driver = { |
| 414 | .name = DRV_NAME, |
| 415 | }, |
| 416 | .probe = cros_ec_accel_legacy_probe, |
| 417 | }; |
| 418 | module_platform_driver(cros_ec_accel_platform_driver); |
| 419 | |
| 420 | MODULE_DESCRIPTION("ChromeOS EC legacy accelerometer driver"); |
| 421 | MODULE_AUTHOR("Gwendal Grignou <gwendal@chromium.org>"); |
| 422 | MODULE_LICENSE("GPL"); |
| 423 | MODULE_ALIAS("platform:" DRV_NAME); |