1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * IIO rescale driver 4 * 5 * Copyright (C) 2018 Axentia Technologies AB 6 * Copyright (C) 2022 Liam Beguin <liambeguin@gmail.com> 7 * 8 * Author: Peter Rosin <peda@axentia.se> 9 */ 10 11 #include <linux/err.h> 12 #include <linux/gcd.h> 13 #include <linux/mod_devicetable.h> 14 #include <linux/module.h> 15 #include <linux/platform_device.h> 16 #include <linux/property.h> 17 18 #include <linux/iio/afe/rescale.h> 19 #include <linux/iio/consumer.h> 20 #include <linux/iio/iio.h> 21 22 int rescale_process_scale(struct rescale *rescale, int scale_type, 23 int *val, int *val2) 24 { 25 s64 tmp; 26 int _val, _val2; 27 s32 rem, rem2; 28 u32 mult; 29 u32 neg; 30 31 switch (scale_type) { 32 case IIO_VAL_INT: 33 *val *= rescale->numerator; 34 if (rescale->denominator == 1) 35 return scale_type; 36 *val2 = rescale->denominator; 37 return IIO_VAL_FRACTIONAL; 38 case IIO_VAL_FRACTIONAL: 39 /* 40 * When the product of both scales doesn't overflow, avoid 41 * potential accuracy loss (for in kernel consumers) by 42 * keeping a fractional representation. 43 */ 44 if (!check_mul_overflow(*val, rescale->numerator, &_val) && 45 !check_mul_overflow(*val2, rescale->denominator, &_val2)) { 46 *val = _val; 47 *val2 = _val2; 48 return IIO_VAL_FRACTIONAL; 49 } 50 fallthrough; 51 case IIO_VAL_FRACTIONAL_LOG2: 52 tmp = (s64)*val * 1000000000LL; 53 tmp = div_s64(tmp, rescale->denominator); 54 tmp *= rescale->numerator; 55 56 tmp = div_s64_rem(tmp, 1000000000LL, &rem); 57 *val = tmp; 58 59 if (!rem) 60 return scale_type; 61 62 if (scale_type == IIO_VAL_FRACTIONAL) 63 tmp = *val2; 64 else 65 tmp = ULL(1) << *val2; 66 67 rem2 = *val % (int)tmp; 68 *val = *val / (int)tmp; 69 70 *val2 = rem / (int)tmp; 71 if (rem2) 72 *val2 += div_s64((s64)rem2 * 1000000000LL, tmp); 73 74 return IIO_VAL_INT_PLUS_NANO; 75 case IIO_VAL_INT_PLUS_NANO: 76 case IIO_VAL_INT_PLUS_MICRO: 77 mult = scale_type == IIO_VAL_INT_PLUS_NANO ? 1000000000L : 1000000L; 78 79 /* 80 * For IIO_VAL_INT_PLUS_{MICRO,NANO} scale types if either *val 81 * OR *val2 is negative the schan scale is negative, i.e. 82 * *val = 1 and *val2 = -0.5 yields -1.5 not -0.5. 83 */ 84 neg = *val < 0 || *val2 < 0; 85 86 tmp = (s64)abs(*val) * abs(rescale->numerator); 87 *val = div_s64_rem(tmp, abs(rescale->denominator), &rem); 88 89 tmp = (s64)rem * mult + (s64)abs(*val2) * abs(rescale->numerator); 90 tmp = div_s64(tmp, abs(rescale->denominator)); 91 92 *val += div_s64_rem(tmp, mult, val2); 93 94 /* 95 * If only one of the rescaler elements or the schan scale is 96 * negative, the combined scale is negative. 97 */ 98 if (neg ^ ((rescale->numerator < 0) ^ (rescale->denominator < 0))) { 99 if (*val) 100 *val = -*val; 101 else 102 *val2 = -*val2; 103 } 104 105 return scale_type; 106 default: 107 return -EOPNOTSUPP; 108 } 109 } 110 EXPORT_SYMBOL_NS_GPL(rescale_process_scale, IIO_RESCALE); 111 112 int rescale_process_offset(struct rescale *rescale, int scale_type, 113 int scale, int scale2, int schan_off, 114 int *val, int *val2) 115 { 116 s64 tmp, tmp2; 117 118 switch (scale_type) { 119 case IIO_VAL_FRACTIONAL: 120 tmp = (s64)rescale->offset * scale2; 121 *val = div_s64(tmp, scale) + schan_off; 122 return IIO_VAL_INT; 123 case IIO_VAL_INT: 124 *val = div_s64(rescale->offset, scale) + schan_off; 125 return IIO_VAL_INT; 126 case IIO_VAL_FRACTIONAL_LOG2: 127 tmp = (s64)rescale->offset * (1 << scale2); 128 *val = div_s64(tmp, scale) + schan_off; 129 return IIO_VAL_INT; 130 case IIO_VAL_INT_PLUS_NANO: 131 tmp = (s64)rescale->offset * 1000000000LL; 132 tmp2 = ((s64)scale * 1000000000LL) + scale2; 133 *val = div64_s64(tmp, tmp2) + schan_off; 134 return IIO_VAL_INT; 135 case IIO_VAL_INT_PLUS_MICRO: 136 tmp = (s64)rescale->offset * 1000000LL; 137 tmp2 = ((s64)scale * 1000000LL) + scale2; 138 *val = div64_s64(tmp, tmp2) + schan_off; 139 return IIO_VAL_INT; 140 default: 141 return -EOPNOTSUPP; 142 } 143 } 144 EXPORT_SYMBOL_NS_GPL(rescale_process_offset, IIO_RESCALE); 145 146 static int rescale_read_raw(struct iio_dev *indio_dev, 147 struct iio_chan_spec const *chan, 148 int *val, int *val2, long mask) 149 { 150 struct rescale *rescale = iio_priv(indio_dev); 151 int scale, scale2; 152 int schan_off = 0; 153 int ret; 154 155 switch (mask) { 156 case IIO_CHAN_INFO_RAW: 157 if (rescale->chan_processed) 158 /* 159 * When only processed channels are supported, we 160 * read the processed data and scale it by 1/1 161 * augmented with whatever the rescaler has calculated. 162 */ 163 return iio_read_channel_processed(rescale->source, val); 164 else 165 return iio_read_channel_raw(rescale->source, val); 166 167 case IIO_CHAN_INFO_SCALE: 168 if (rescale->chan_processed) { 169 /* 170 * Processed channels are scaled 1-to-1 171 */ 172 *val = 1; 173 *val2 = 1; 174 ret = IIO_VAL_FRACTIONAL; 175 } else { 176 ret = iio_read_channel_scale(rescale->source, val, val2); 177 } 178 return rescale_process_scale(rescale, ret, val, val2); 179 case IIO_CHAN_INFO_OFFSET: 180 /* 181 * Processed channels are scaled 1-to-1 and source offset is 182 * already taken into account. 183 * 184 * In other cases, real world measurement are expressed as: 185 * 186 * schan_scale * (raw + schan_offset) 187 * 188 * Given that the rescaler parameters are applied recursively: 189 * 190 * rescaler_scale * (schan_scale * (raw + schan_offset) + 191 * rescaler_offset) 192 * 193 * Or, 194 * 195 * (rescaler_scale * schan_scale) * (raw + 196 * (schan_offset + rescaler_offset / schan_scale) 197 * 198 * Thus, reusing the original expression the parameters exposed 199 * to userspace are: 200 * 201 * scale = schan_scale * rescaler_scale 202 * offset = schan_offset + rescaler_offset / schan_scale 203 */ 204 if (rescale->chan_processed) { 205 *val = rescale->offset; 206 return IIO_VAL_INT; 207 } 208 209 if (iio_channel_has_info(rescale->source->channel, 210 IIO_CHAN_INFO_OFFSET)) { 211 ret = iio_read_channel_offset(rescale->source, 212 &schan_off, NULL); 213 if (ret != IIO_VAL_INT) 214 return ret < 0 ? ret : -EOPNOTSUPP; 215 } 216 217 ret = iio_read_channel_scale(rescale->source, &scale, &scale2); 218 return rescale_process_offset(rescale, ret, scale, scale2, 219 schan_off, val, val2); 220 default: 221 return -EINVAL; 222 } 223 } 224 225 static int rescale_read_avail(struct iio_dev *indio_dev, 226 struct iio_chan_spec const *chan, 227 const int **vals, int *type, int *length, 228 long mask) 229 { 230 struct rescale *rescale = iio_priv(indio_dev); 231 232 switch (mask) { 233 case IIO_CHAN_INFO_RAW: 234 *type = IIO_VAL_INT; 235 return iio_read_avail_channel_raw(rescale->source, 236 vals, length); 237 default: 238 return -EINVAL; 239 } 240 } 241 242 static const struct iio_info rescale_info = { 243 .read_raw = rescale_read_raw, 244 .read_avail = rescale_read_avail, 245 }; 246 247 static ssize_t rescale_read_ext_info(struct iio_dev *indio_dev, 248 uintptr_t private, 249 struct iio_chan_spec const *chan, 250 char *buf) 251 { 252 struct rescale *rescale = iio_priv(indio_dev); 253 254 return iio_read_channel_ext_info(rescale->source, 255 rescale->ext_info[private].name, 256 buf); 257 } 258 259 static ssize_t rescale_write_ext_info(struct iio_dev *indio_dev, 260 uintptr_t private, 261 struct iio_chan_spec const *chan, 262 const char *buf, size_t len) 263 { 264 struct rescale *rescale = iio_priv(indio_dev); 265 266 return iio_write_channel_ext_info(rescale->source, 267 rescale->ext_info[private].name, 268 buf, len); 269 } 270 271 static int rescale_configure_channel(struct device *dev, 272 struct rescale *rescale) 273 { 274 struct iio_chan_spec *chan = &rescale->chan; 275 struct iio_chan_spec const *schan = rescale->source->channel; 276 277 chan->indexed = 1; 278 chan->output = schan->output; 279 chan->ext_info = rescale->ext_info; 280 chan->type = rescale->cfg->type; 281 282 if (iio_channel_has_info(schan, IIO_CHAN_INFO_RAW) && 283 iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE)) { 284 dev_info(dev, "using raw+scale source channel\n"); 285 } else if (iio_channel_has_info(schan, IIO_CHAN_INFO_PROCESSED)) { 286 dev_info(dev, "using processed channel\n"); 287 rescale->chan_processed = true; 288 } else { 289 dev_err(dev, "source channel is not supported\n"); 290 return -EINVAL; 291 } 292 293 chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | 294 BIT(IIO_CHAN_INFO_SCALE); 295 296 if (rescale->offset) 297 chan->info_mask_separate |= BIT(IIO_CHAN_INFO_OFFSET); 298 299 /* 300 * Using .read_avail() is fringe to begin with and makes no sense 301 * whatsoever for processed channels, so we make sure that this cannot 302 * be called on a processed channel. 303 */ 304 if (iio_channel_has_available(schan, IIO_CHAN_INFO_RAW) && 305 !rescale->chan_processed) 306 chan->info_mask_separate_available |= BIT(IIO_CHAN_INFO_RAW); 307 308 return 0; 309 } 310 311 static int rescale_current_sense_amplifier_props(struct device *dev, 312 struct rescale *rescale) 313 { 314 u32 sense; 315 u32 gain_mult = 1; 316 u32 gain_div = 1; 317 u32 factor; 318 int ret; 319 320 ret = device_property_read_u32(dev, "sense-resistor-micro-ohms", 321 &sense); 322 if (ret) { 323 dev_err(dev, "failed to read the sense resistance: %d\n", ret); 324 return ret; 325 } 326 327 device_property_read_u32(dev, "sense-gain-mult", &gain_mult); 328 device_property_read_u32(dev, "sense-gain-div", &gain_div); 329 330 /* 331 * Calculate the scaling factor, 1 / (gain * sense), or 332 * gain_div / (gain_mult * sense), while trying to keep the 333 * numerator/denominator from overflowing. 334 */ 335 factor = gcd(sense, 1000000); 336 rescale->numerator = 1000000 / factor; 337 rescale->denominator = sense / factor; 338 339 factor = gcd(rescale->numerator, gain_mult); 340 rescale->numerator /= factor; 341 rescale->denominator *= gain_mult / factor; 342 343 factor = gcd(rescale->denominator, gain_div); 344 rescale->numerator *= gain_div / factor; 345 rescale->denominator /= factor; 346 347 return 0; 348 } 349 350 static int rescale_current_sense_shunt_props(struct device *dev, 351 struct rescale *rescale) 352 { 353 u32 shunt; 354 u32 factor; 355 int ret; 356 357 ret = device_property_read_u32(dev, "shunt-resistor-micro-ohms", 358 &shunt); 359 if (ret) { 360 dev_err(dev, "failed to read the shunt resistance: %d\n", ret); 361 return ret; 362 } 363 364 factor = gcd(shunt, 1000000); 365 rescale->numerator = 1000000 / factor; 366 rescale->denominator = shunt / factor; 367 368 return 0; 369 } 370 371 static int rescale_voltage_divider_props(struct device *dev, 372 struct rescale *rescale) 373 { 374 int ret; 375 u32 factor; 376 377 ret = device_property_read_u32(dev, "output-ohms", 378 &rescale->denominator); 379 if (ret) { 380 dev_err(dev, "failed to read output-ohms: %d\n", ret); 381 return ret; 382 } 383 384 ret = device_property_read_u32(dev, "full-ohms", 385 &rescale->numerator); 386 if (ret) { 387 dev_err(dev, "failed to read full-ohms: %d\n", ret); 388 return ret; 389 } 390 391 factor = gcd(rescale->numerator, rescale->denominator); 392 rescale->numerator /= factor; 393 rescale->denominator /= factor; 394 395 return 0; 396 } 397 398 static int rescale_temp_sense_rtd_props(struct device *dev, 399 struct rescale *rescale) 400 { 401 u32 factor; 402 u32 alpha; 403 u32 iexc; 404 u32 tmp; 405 int ret; 406 u32 r0; 407 408 ret = device_property_read_u32(dev, "excitation-current-microamp", 409 &iexc); 410 if (ret) { 411 dev_err(dev, "failed to read excitation-current-microamp: %d\n", 412 ret); 413 return ret; 414 } 415 416 ret = device_property_read_u32(dev, "alpha-ppm-per-celsius", &alpha); 417 if (ret) { 418 dev_err(dev, "failed to read alpha-ppm-per-celsius: %d\n", 419 ret); 420 return ret; 421 } 422 423 ret = device_property_read_u32(dev, "r-naught-ohms", &r0); 424 if (ret) { 425 dev_err(dev, "failed to read r-naught-ohms: %d\n", ret); 426 return ret; 427 } 428 429 tmp = r0 * iexc * alpha / 1000000; 430 factor = gcd(tmp, 1000000); 431 rescale->numerator = 1000000 / factor; 432 rescale->denominator = tmp / factor; 433 434 rescale->offset = -1 * ((r0 * iexc) / 1000); 435 436 return 0; 437 } 438 439 static int rescale_temp_transducer_props(struct device *dev, 440 struct rescale *rescale) 441 { 442 s32 offset = 0; 443 s32 sense = 1; 444 s32 alpha; 445 int ret; 446 447 device_property_read_u32(dev, "sense-offset-millicelsius", &offset); 448 device_property_read_u32(dev, "sense-resistor-ohms", &sense); 449 ret = device_property_read_u32(dev, "alpha-ppm-per-celsius", &alpha); 450 if (ret) { 451 dev_err(dev, "failed to read alpha-ppm-per-celsius: %d\n", ret); 452 return ret; 453 } 454 455 rescale->numerator = 1000000; 456 rescale->denominator = alpha * sense; 457 458 rescale->offset = div_s64((s64)offset * rescale->denominator, 459 rescale->numerator); 460 461 return 0; 462 } 463 464 enum rescale_variant { 465 CURRENT_SENSE_AMPLIFIER, 466 CURRENT_SENSE_SHUNT, 467 VOLTAGE_DIVIDER, 468 TEMP_SENSE_RTD, 469 TEMP_TRANSDUCER, 470 }; 471 472 static const struct rescale_cfg rescale_cfg[] = { 473 [CURRENT_SENSE_AMPLIFIER] = { 474 .type = IIO_CURRENT, 475 .props = rescale_current_sense_amplifier_props, 476 }, 477 [CURRENT_SENSE_SHUNT] = { 478 .type = IIO_CURRENT, 479 .props = rescale_current_sense_shunt_props, 480 }, 481 [VOLTAGE_DIVIDER] = { 482 .type = IIO_VOLTAGE, 483 .props = rescale_voltage_divider_props, 484 }, 485 [TEMP_SENSE_RTD] = { 486 .type = IIO_TEMP, 487 .props = rescale_temp_sense_rtd_props, 488 }, 489 [TEMP_TRANSDUCER] = { 490 .type = IIO_TEMP, 491 .props = rescale_temp_transducer_props, 492 }, 493 }; 494 495 static const struct of_device_id rescale_match[] = { 496 { .compatible = "current-sense-amplifier", 497 .data = &rescale_cfg[CURRENT_SENSE_AMPLIFIER], }, 498 { .compatible = "current-sense-shunt", 499 .data = &rescale_cfg[CURRENT_SENSE_SHUNT], }, 500 { .compatible = "voltage-divider", 501 .data = &rescale_cfg[VOLTAGE_DIVIDER], }, 502 { .compatible = "temperature-sense-rtd", 503 .data = &rescale_cfg[TEMP_SENSE_RTD], }, 504 { .compatible = "temperature-transducer", 505 .data = &rescale_cfg[TEMP_TRANSDUCER], }, 506 { /* sentinel */ } 507 }; 508 MODULE_DEVICE_TABLE(of, rescale_match); 509 510 static int rescale_probe(struct platform_device *pdev) 511 { 512 struct device *dev = &pdev->dev; 513 struct iio_dev *indio_dev; 514 struct iio_channel *source; 515 struct rescale *rescale; 516 int sizeof_ext_info; 517 int sizeof_priv; 518 int i; 519 int ret; 520 521 source = devm_iio_channel_get(dev, NULL); 522 if (IS_ERR(source)) 523 return dev_err_probe(dev, PTR_ERR(source), 524 "failed to get source channel\n"); 525 526 sizeof_ext_info = iio_get_channel_ext_info_count(source); 527 if (sizeof_ext_info) { 528 sizeof_ext_info += 1; /* one extra entry for the sentinel */ 529 sizeof_ext_info *= sizeof(*rescale->ext_info); 530 } 531 532 sizeof_priv = sizeof(*rescale) + sizeof_ext_info; 533 534 indio_dev = devm_iio_device_alloc(dev, sizeof_priv); 535 if (!indio_dev) 536 return -ENOMEM; 537 538 rescale = iio_priv(indio_dev); 539 540 rescale->cfg = device_get_match_data(dev); 541 rescale->numerator = 1; 542 rescale->denominator = 1; 543 rescale->offset = 0; 544 545 ret = rescale->cfg->props(dev, rescale); 546 if (ret) 547 return ret; 548 549 if (!rescale->numerator || !rescale->denominator) { 550 dev_err(dev, "invalid scaling factor.\n"); 551 return -EINVAL; 552 } 553 554 platform_set_drvdata(pdev, indio_dev); 555 556 rescale->source = source; 557 558 indio_dev->name = dev_name(dev); 559 indio_dev->info = &rescale_info; 560 indio_dev->modes = INDIO_DIRECT_MODE; 561 indio_dev->channels = &rescale->chan; 562 indio_dev->num_channels = 1; 563 if (sizeof_ext_info) { 564 rescale->ext_info = devm_kmemdup(dev, 565 source->channel->ext_info, 566 sizeof_ext_info, GFP_KERNEL); 567 if (!rescale->ext_info) 568 return -ENOMEM; 569 570 for (i = 0; rescale->ext_info[i].name; ++i) { 571 struct iio_chan_spec_ext_info *ext_info = 572 &rescale->ext_info[i]; 573 574 if (source->channel->ext_info[i].read) 575 ext_info->read = rescale_read_ext_info; 576 if (source->channel->ext_info[i].write) 577 ext_info->write = rescale_write_ext_info; 578 ext_info->private = i; 579 } 580 } 581 582 ret = rescale_configure_channel(dev, rescale); 583 if (ret) 584 return ret; 585 586 return devm_iio_device_register(dev, indio_dev); 587 } 588 589 static struct platform_driver rescale_driver = { 590 .probe = rescale_probe, 591 .driver = { 592 .name = "iio-rescale", 593 .of_match_table = rescale_match, 594 }, 595 }; 596 module_platform_driver(rescale_driver); 597 598 MODULE_DESCRIPTION("IIO rescale driver"); 599 MODULE_AUTHOR("Peter Rosin <peda@axentia.se>"); 600 MODULE_LICENSE("GPL v2"); 601