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); 424