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
rescale_process_scale(struct rescale * rescale,int scale_type,int * val,int * val2)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
rescale_process_offset(struct rescale * rescale,int scale_type,int scale,int scale2,int schan_off,int * val,int * val2)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
rescale_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long mask)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 if (iio_channel_has_info(rescale->source->channel,
218 IIO_CHAN_INFO_SCALE)) {
219 ret = iio_read_channel_scale(rescale->source, &scale, &scale2);
220 return rescale_process_offset(rescale, ret, scale, scale2,
221 schan_off, val, val2);
222 }
223
224 /*
225 * If we get here we have no scale so scale 1:1 but apply
226 * rescaler and offset, if any.
227 */
228 return rescale_process_offset(rescale, IIO_VAL_FRACTIONAL, 1, 1,
229 schan_off, val, val2);
230 default:
231 return -EINVAL;
232 }
233 }
234
rescale_read_avail(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,const int ** vals,int * type,int * length,long mask)235 static int rescale_read_avail(struct iio_dev *indio_dev,
236 struct iio_chan_spec const *chan,
237 const int **vals, int *type, int *length,
238 long mask)
239 {
240 struct rescale *rescale = iio_priv(indio_dev);
241
242 switch (mask) {
243 case IIO_CHAN_INFO_RAW:
244 *type = IIO_VAL_INT;
245 return iio_read_avail_channel_raw(rescale->source,
246 vals, length);
247 default:
248 return -EINVAL;
249 }
250 }
251
252 static const struct iio_info rescale_info = {
253 .read_raw = rescale_read_raw,
254 .read_avail = rescale_read_avail,
255 };
256
rescale_read_ext_info(struct iio_dev * indio_dev,uintptr_t private,struct iio_chan_spec const * chan,char * buf)257 static ssize_t rescale_read_ext_info(struct iio_dev *indio_dev,
258 uintptr_t private,
259 struct iio_chan_spec const *chan,
260 char *buf)
261 {
262 struct rescale *rescale = iio_priv(indio_dev);
263
264 return iio_read_channel_ext_info(rescale->source,
265 rescale->ext_info[private].name,
266 buf);
267 }
268
rescale_write_ext_info(struct iio_dev * indio_dev,uintptr_t private,struct iio_chan_spec const * chan,const char * buf,size_t len)269 static ssize_t rescale_write_ext_info(struct iio_dev *indio_dev,
270 uintptr_t private,
271 struct iio_chan_spec const *chan,
272 const char *buf, size_t len)
273 {
274 struct rescale *rescale = iio_priv(indio_dev);
275
276 return iio_write_channel_ext_info(rescale->source,
277 rescale->ext_info[private].name,
278 buf, len);
279 }
280
rescale_configure_channel(struct device * dev,struct rescale * rescale)281 static int rescale_configure_channel(struct device *dev,
282 struct rescale *rescale)
283 {
284 struct iio_chan_spec *chan = &rescale->chan;
285 struct iio_chan_spec const *schan = rescale->source->channel;
286
287 chan->indexed = 1;
288 chan->output = schan->output;
289 chan->ext_info = rescale->ext_info;
290 chan->type = rescale->cfg->type;
291
292 if (iio_channel_has_info(schan, IIO_CHAN_INFO_RAW) &&
293 (iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE) ||
294 iio_channel_has_info(schan, IIO_CHAN_INFO_OFFSET))) {
295 dev_info(dev, "using raw+scale/offset source channel\n");
296 } else if (iio_channel_has_info(schan, IIO_CHAN_INFO_PROCESSED)) {
297 dev_info(dev, "using processed channel\n");
298 rescale->chan_processed = true;
299 } else {
300 dev_err(dev, "source channel is not supported\n");
301 return -EINVAL;
302 }
303
304 chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
305 BIT(IIO_CHAN_INFO_SCALE);
306
307 if (rescale->offset)
308 chan->info_mask_separate |= BIT(IIO_CHAN_INFO_OFFSET);
309
310 /*
311 * Using .read_avail() is fringe to begin with and makes no sense
312 * whatsoever for processed channels, so we make sure that this cannot
313 * be called on a processed channel.
314 */
315 if (iio_channel_has_available(schan, IIO_CHAN_INFO_RAW) &&
316 !rescale->chan_processed)
317 chan->info_mask_separate_available |= BIT(IIO_CHAN_INFO_RAW);
318
319 return 0;
320 }
321
rescale_current_sense_amplifier_props(struct device * dev,struct rescale * rescale)322 static int rescale_current_sense_amplifier_props(struct device *dev,
323 struct rescale *rescale)
324 {
325 u32 sense;
326 u32 gain_mult = 1;
327 u32 gain_div = 1;
328 u32 factor;
329 int ret;
330
331 ret = device_property_read_u32(dev, "sense-resistor-micro-ohms",
332 &sense);
333 if (ret) {
334 dev_err(dev, "failed to read the sense resistance: %d\n", ret);
335 return ret;
336 }
337
338 device_property_read_u32(dev, "sense-gain-mult", &gain_mult);
339 device_property_read_u32(dev, "sense-gain-div", &gain_div);
340
341 /*
342 * Calculate the scaling factor, 1 / (gain * sense), or
343 * gain_div / (gain_mult * sense), while trying to keep the
344 * numerator/denominator from overflowing.
345 */
346 factor = gcd(sense, 1000000);
347 rescale->numerator = 1000000 / factor;
348 rescale->denominator = sense / factor;
349
350 factor = gcd(rescale->numerator, gain_mult);
351 rescale->numerator /= factor;
352 rescale->denominator *= gain_mult / factor;
353
354 factor = gcd(rescale->denominator, gain_div);
355 rescale->numerator *= gain_div / factor;
356 rescale->denominator /= factor;
357
358 return 0;
359 }
360
rescale_current_sense_shunt_props(struct device * dev,struct rescale * rescale)361 static int rescale_current_sense_shunt_props(struct device *dev,
362 struct rescale *rescale)
363 {
364 u32 shunt;
365 u32 factor;
366 int ret;
367
368 ret = device_property_read_u32(dev, "shunt-resistor-micro-ohms",
369 &shunt);
370 if (ret) {
371 dev_err(dev, "failed to read the shunt resistance: %d\n", ret);
372 return ret;
373 }
374
375 factor = gcd(shunt, 1000000);
376 rescale->numerator = 1000000 / factor;
377 rescale->denominator = shunt / factor;
378
379 return 0;
380 }
381
rescale_voltage_divider_props(struct device * dev,struct rescale * rescale)382 static int rescale_voltage_divider_props(struct device *dev,
383 struct rescale *rescale)
384 {
385 int ret;
386 u32 factor;
387
388 ret = device_property_read_u32(dev, "output-ohms",
389 &rescale->denominator);
390 if (ret) {
391 dev_err(dev, "failed to read output-ohms: %d\n", ret);
392 return ret;
393 }
394
395 ret = device_property_read_u32(dev, "full-ohms",
396 &rescale->numerator);
397 if (ret) {
398 dev_err(dev, "failed to read full-ohms: %d\n", ret);
399 return ret;
400 }
401
402 factor = gcd(rescale->numerator, rescale->denominator);
403 rescale->numerator /= factor;
404 rescale->denominator /= factor;
405
406 return 0;
407 }
408
rescale_temp_sense_rtd_props(struct device * dev,struct rescale * rescale)409 static int rescale_temp_sense_rtd_props(struct device *dev,
410 struct rescale *rescale)
411 {
412 u32 factor;
413 u32 alpha;
414 u32 iexc;
415 u32 tmp;
416 int ret;
417 u32 r0;
418
419 ret = device_property_read_u32(dev, "excitation-current-microamp",
420 &iexc);
421 if (ret) {
422 dev_err(dev, "failed to read excitation-current-microamp: %d\n",
423 ret);
424 return ret;
425 }
426
427 ret = device_property_read_u32(dev, "alpha-ppm-per-celsius", &alpha);
428 if (ret) {
429 dev_err(dev, "failed to read alpha-ppm-per-celsius: %d\n",
430 ret);
431 return ret;
432 }
433
434 ret = device_property_read_u32(dev, "r-naught-ohms", &r0);
435 if (ret) {
436 dev_err(dev, "failed to read r-naught-ohms: %d\n", ret);
437 return ret;
438 }
439
440 tmp = r0 * iexc * alpha / 1000000;
441 factor = gcd(tmp, 1000000);
442 rescale->numerator = 1000000 / factor;
443 rescale->denominator = tmp / factor;
444
445 rescale->offset = -1 * ((r0 * iexc) / 1000);
446
447 return 0;
448 }
449
rescale_temp_transducer_props(struct device * dev,struct rescale * rescale)450 static int rescale_temp_transducer_props(struct device *dev,
451 struct rescale *rescale)
452 {
453 s32 offset = 0;
454 s32 sense = 1;
455 s32 alpha;
456 int ret;
457
458 device_property_read_u32(dev, "sense-offset-millicelsius", &offset);
459 device_property_read_u32(dev, "sense-resistor-ohms", &sense);
460 ret = device_property_read_u32(dev, "alpha-ppm-per-celsius", &alpha);
461 if (ret) {
462 dev_err(dev, "failed to read alpha-ppm-per-celsius: %d\n", ret);
463 return ret;
464 }
465
466 rescale->numerator = 1000000;
467 rescale->denominator = alpha * sense;
468
469 rescale->offset = div_s64((s64)offset * rescale->denominator,
470 rescale->numerator);
471
472 return 0;
473 }
474
475 enum rescale_variant {
476 CURRENT_SENSE_AMPLIFIER,
477 CURRENT_SENSE_SHUNT,
478 VOLTAGE_DIVIDER,
479 TEMP_SENSE_RTD,
480 TEMP_TRANSDUCER,
481 };
482
483 static const struct rescale_cfg rescale_cfg[] = {
484 [CURRENT_SENSE_AMPLIFIER] = {
485 .type = IIO_CURRENT,
486 .props = rescale_current_sense_amplifier_props,
487 },
488 [CURRENT_SENSE_SHUNT] = {
489 .type = IIO_CURRENT,
490 .props = rescale_current_sense_shunt_props,
491 },
492 [VOLTAGE_DIVIDER] = {
493 .type = IIO_VOLTAGE,
494 .props = rescale_voltage_divider_props,
495 },
496 [TEMP_SENSE_RTD] = {
497 .type = IIO_TEMP,
498 .props = rescale_temp_sense_rtd_props,
499 },
500 [TEMP_TRANSDUCER] = {
501 .type = IIO_TEMP,
502 .props = rescale_temp_transducer_props,
503 },
504 };
505
506 static const struct of_device_id rescale_match[] = {
507 { .compatible = "current-sense-amplifier",
508 .data = &rescale_cfg[CURRENT_SENSE_AMPLIFIER], },
509 { .compatible = "current-sense-shunt",
510 .data = &rescale_cfg[CURRENT_SENSE_SHUNT], },
511 { .compatible = "voltage-divider",
512 .data = &rescale_cfg[VOLTAGE_DIVIDER], },
513 { .compatible = "temperature-sense-rtd",
514 .data = &rescale_cfg[TEMP_SENSE_RTD], },
515 { .compatible = "temperature-transducer",
516 .data = &rescale_cfg[TEMP_TRANSDUCER], },
517 { /* sentinel */ }
518 };
519 MODULE_DEVICE_TABLE(of, rescale_match);
520
rescale_probe(struct platform_device * pdev)521 static int rescale_probe(struct platform_device *pdev)
522 {
523 struct device *dev = &pdev->dev;
524 struct iio_dev *indio_dev;
525 struct iio_channel *source;
526 struct rescale *rescale;
527 int sizeof_ext_info;
528 int sizeof_priv;
529 int i;
530 int ret;
531
532 source = devm_iio_channel_get(dev, NULL);
533 if (IS_ERR(source))
534 return dev_err_probe(dev, PTR_ERR(source),
535 "failed to get source channel\n");
536
537 sizeof_ext_info = iio_get_channel_ext_info_count(source);
538 if (sizeof_ext_info) {
539 sizeof_ext_info += 1; /* one extra entry for the sentinel */
540 sizeof_ext_info *= sizeof(*rescale->ext_info);
541 }
542
543 sizeof_priv = sizeof(*rescale) + sizeof_ext_info;
544
545 indio_dev = devm_iio_device_alloc(dev, sizeof_priv);
546 if (!indio_dev)
547 return -ENOMEM;
548
549 rescale = iio_priv(indio_dev);
550
551 rescale->cfg = device_get_match_data(dev);
552 rescale->numerator = 1;
553 rescale->denominator = 1;
554 rescale->offset = 0;
555
556 ret = rescale->cfg->props(dev, rescale);
557 if (ret)
558 return ret;
559
560 if (!rescale->numerator || !rescale->denominator) {
561 dev_err(dev, "invalid scaling factor.\n");
562 return -EINVAL;
563 }
564
565 platform_set_drvdata(pdev, indio_dev);
566
567 rescale->source = source;
568
569 indio_dev->name = dev_name(dev);
570 indio_dev->info = &rescale_info;
571 indio_dev->modes = INDIO_DIRECT_MODE;
572 indio_dev->channels = &rescale->chan;
573 indio_dev->num_channels = 1;
574 if (sizeof_ext_info) {
575 rescale->ext_info = devm_kmemdup(dev,
576 source->channel->ext_info,
577 sizeof_ext_info, GFP_KERNEL);
578 if (!rescale->ext_info)
579 return -ENOMEM;
580
581 for (i = 0; rescale->ext_info[i].name; ++i) {
582 struct iio_chan_spec_ext_info *ext_info =
583 &rescale->ext_info[i];
584
585 if (source->channel->ext_info[i].read)
586 ext_info->read = rescale_read_ext_info;
587 if (source->channel->ext_info[i].write)
588 ext_info->write = rescale_write_ext_info;
589 ext_info->private = i;
590 }
591 }
592
593 ret = rescale_configure_channel(dev, rescale);
594 if (ret)
595 return ret;
596
597 return devm_iio_device_register(dev, indio_dev);
598 }
599
600 static struct platform_driver rescale_driver = {
601 .probe = rescale_probe,
602 .driver = {
603 .name = "iio-rescale",
604 .of_match_table = rescale_match,
605 },
606 };
607 module_platform_driver(rescale_driver);
608
609 MODULE_DESCRIPTION("IIO rescale driver");
610 MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
611 MODULE_LICENSE("GPL v2");
612