[PATCH v12 00/16] iio: afe: add temperature rescaling support

[PATCH v12 00/16] iio: afe: add temperature rescaling support

[Liam Beguin]

Jonathan, Peter, Andy,

I left out IIO_VAL_INT overflows for now, so that I can focus on getting
the rest of these changes pulled in, but I don't mind adding a patch for
that later on.

This series focuses on adding temperature rescaling support to the IIO
Analog Front End (AFE) driver.

The first few patches address minor bugs in IIO inkernel functions, and
prepare the AFE driver for the additional features.

The main changes to the AFE driver include an initial Kunit test suite,
support for IIO_VAL_INT_PLUS_{NANO,MICRO} scales, and support for RTDs
and temperature transducer sensors.

My apologies Andy for misunderstanding your left-shift comments, I don't
know where my head was at... Thanks for your patience!

Thanks you all again for your time, and Happy New Year!
Liam

Changes since v11:
- update commits with my personal email since all this work was done on
  my own time
- apply Peter's Reviewed-by to my local tree
- fix use of units.h
- make use of units.h more consistently in iio-rescale.c and in the
  tests
- fix #include ordering
- treat 04/16 as a fix. Move it, and add a Fixes: tag
- fix undefined behavior on left-shift operation
- add comment about fract_mult with iio_str_to_fixpoint()
- reword commit message for 14/16, based on Andy's comments

Changes since v10:
- apply Andy's suggestion for offset calculations
- make use of units.h more consistently

Changes since v9:
- make use of linux/units.h
- reorder commits, fix fract_log2 before merging fract
- keep fractional representation when not overflowing

Changes since v8:
- reword comment
- fix erroneous 64-bit division
- optimize and use 32-bit divisions when values are know to not overflow
- keep IIO_VAL_FRACTIONAL scale when possible, if not default to fixed
  point
- add test cases
- use nano precision in test cases
- simplify offset calculation in rtd_props()

Changes since v7:
- drop gcd() logic in rescale_process_scale()
- use div_s64() instead of do_div() for signed 64-bit divisions
- combine IIO_VAL_FRACTIONAL and IIO_VAL_FRACTIONAL_LOG2 scale cases
- switch to INT_PLUS_NANO when accuracy is lost with FRACTIONAL scales
- rework test logic to allow for small relative error
- rename test variables to align error output messages

Changes since v6:
- rework IIO_VAL_INT_PLUS_{NANO,MICRO} based on Peter's suggestion
- combine IIO_VAL_INT_PLUS_{NANO,MICRO} cases
- add test cases for negative IIO_VAL_INT_PLUS_{NANO,MICRO} corner cases
- force use of positive integers with gcd()
- reduce risk of integer overflow in IIO_VAL_FRACTIONAL_LOG2
- fix duplicate symbol build error
- apply Reviewed-by

Changes since v5:
- add include/linux/iio/afe/rescale.h
- expose functions use to process scale and offset
- add basic iio-rescale kunit test cases
- fix integer overflow case
- improve precision for IIO_VAL_FRACTIONAL_LOG2

Changes since v4:
- only use gcd() when necessary in overflow mitigation
- fix INT_PLUS_{MICRO,NANO} support
- apply Reviewed-by
- fix temperature-transducer bindings

Changes since v3:
- drop unnecessary fallthrough statements
- drop redundant local variables in some calculations
- fix s64 divisions on 32bit platforms by using do_div
- add comment describing iio-rescaler offset calculation
- drop unnecessary MAINTAINERS entry

Changes since v2:
- don't break implicit offset truncations
- make a best effort to get a valid value for fractional types
- drop return value change in iio_convert_raw_to_processed_unlocked()
- don't rely on processed value for offset calculation
- add INT_PLUS_{MICRO,NANO} support in iio-rescale
- revert generic implementation in favor of temperature-sense-rtd and
  temperature-transducer
- add separate section to MAINTAINERS file

Changes since v1:
- rebase on latest iio `testing` branch
- also apply consumer scale on integer channel scale types
- don't break implicit truncation in processed channel offset
  calculation
- drop temperature AFE flavors in favor of a simpler generic
  implementation

Liam Beguin (16):
  iio: inkern: apply consumer scale on IIO_VAL_INT cases
  iio: inkern: apply consumer scale when no channel scale is available
  iio: inkern: make a best effort on offset calculation
  iio: afe: rescale: use s64 for temporary scale calculations
  iio: afe: rescale: reorder includes
  iio: afe: rescale: expose scale processing function
  iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support
  iio: afe: rescale: add offset support
  iio: afe: rescale: fix accuracy for small fractional scales
  iio: afe: rescale: reduce risk of integer overflow
  iio: afe: rescale: make use of units.h
  iio: test: add basic tests for the iio-rescale driver
  iio: afe: rescale: add RTD temperature sensor support
  iio: afe: rescale: add temperature transducers
  dt-bindings: iio: afe: add bindings for temperature-sense-rtd
  dt-bindings: iio: afe: add bindings for temperature transducers

 .../iio/afe/temperature-sense-rtd.yaml        | 101 +++
 .../iio/afe/temperature-transducer.yaml       | 114 +++
 drivers/iio/afe/iio-rescale.c                 | 296 +++++++-
 drivers/iio/inkern.c                          |  40 +-
 drivers/iio/test/Kconfig                      |  10 +
 drivers/iio/test/Makefile                     |   1 +
 drivers/iio/test/iio-test-rescale.c           | 711 ++++++++++++++++++
 include/linux/iio/afe/rescale.h               |  36 +
 8 files changed, 1259 insertions(+), 50 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml
 create mode 100644 Documentation/devicetree/bindings/iio/afe/temperature-transducer.yaml
 create mode 100644 drivers/iio/test/iio-test-rescale.c
 create mode 100644 include/linux/iio/afe/rescale.h

Range-diff against v11:
 1:  ae3cc93baee6 !  1:  a8ca9300ef2a iio: inkern: apply consumer scale on IIO_VAL_INT cases
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: inkern: apply consumer scale on IIO_VAL_INT cases
    @@ Commit message
         Make sure to always apply the scaling factor requested by the consumer.
     
         Fixes: 48e44ce0f881 ("iio:inkern: Add function to read the processed value")
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## drivers/iio/inkern.c ##
     @@ drivers/iio/inkern.c: static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
 2:  06f66e7f7403 !  2:  efaeceac8d87 iio: inkern: apply consumer scale when no channel scale is available
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: inkern: apply consumer scale when no channel scale is available
    @@ Commit message
         Make sure to always apply the scaling factor requested by the consumer.
     
         Fixes: adc8ec5ff183 ("iio: inkern: pass through raw values if no scaling")
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## drivers/iio/inkern.c ##
     @@ drivers/iio/inkern.c: static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
 3:  1717b82460c0 !  3:  8131208a4454 iio: inkern: make a best effort on offset calculation
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: inkern: make a best effort on offset calculation
    @@ Commit message
         cases without breaking implicit truncations.
     
         Fixes: 48e44ce0f881 ("iio:inkern: Add function to read the processed value")
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## drivers/iio/inkern.c ##
     @@ drivers/iio/inkern.c: EXPORT_SYMBOL_GPL(iio_read_channel_average_raw);
 -:  ------------ >  4:  06202d8f6481 iio: afe: rescale: use s64 for temporary scale calculations
 -:  ------------ >  5:  87b9d77f0d30 iio: afe: rescale: reorder includes
 4:  6fc26588f651 !  6:  e9bf09ca9703 iio: afe: rescale: expose scale processing function
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: afe: rescale: expose scale processing function
    @@ Commit message
         In preparation for the addition of kunit tests, expose the logic
         responsible for combining channel scales.
     
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## drivers/iio/afe/iio-rescale.c ##
     @@
    - #include <linux/gcd.h>
    - #include <linux/iio/consumer.h>
    - #include <linux/iio/iio.h>
    -+#include <linux/iio/afe/rescale.h>
    - #include <linux/module.h>
    - #include <linux/of.h>
    - #include <linux/of_device.h>
      #include <linux/platform_device.h>
      #include <linux/property.h>
      
    ++#include <linux/iio/afe/rescale.h>
    + #include <linux/iio/consumer.h>
    + #include <linux/iio/iio.h>
    + 
     -struct rescale;
     -
     -struct rescale_cfg {
    @@ drivers/iio/afe/iio-rescale.c
     +int rescale_process_scale(struct rescale *rescale, int scale_type,
     +			  int *val, int *val2)
     +{
    -+	unsigned long long tmp;
    ++	s64 tmp;
      
     -struct rescale {
     -	const struct rescale_cfg *cfg;
    @@ drivers/iio/afe/iio-rescale.c
     +		*val2 = rescale->denominator;
     +		return IIO_VAL_FRACTIONAL;
     +	case IIO_VAL_FRACTIONAL_LOG2:
    -+		tmp = *val * 1000000000LL;
    -+		do_div(tmp, rescale->denominator);
    ++		tmp = (s64)*val * 1000000000LL;
    ++		tmp = div_s64(tmp, rescale->denominator);
     +		tmp *= rescale->numerator;
    -+		do_div(tmp, 1000000000LL);
    ++		tmp = div_s64(tmp, 1000000000LL);
     +		*val = tmp;
     +		return scale_type;
     +	default:
    @@ drivers/iio/afe/iio-rescale.c
      			    int *val, int *val2, long mask)
      {
      	struct rescale *rescale = iio_priv(indio_dev);
    --	unsigned long long tmp;
    +-	s64 tmp;
      	int ret;
      
      	switch (mask) {
    @@ drivers/iio/afe/iio-rescale.c: static int rescale_read_raw(struct iio_dev *indio
     -			*val2 = rescale->denominator;
     -			return IIO_VAL_FRACTIONAL;
     -		case IIO_VAL_FRACTIONAL_LOG2:
    --			tmp = *val * 1000000000LL;
    --			do_div(tmp, rescale->denominator);
    +-			tmp = (s64)*val * 1000000000LL;
    +-			tmp = div_s64(tmp, rescale->denominator);
     -			tmp *= rescale->numerator;
    --			do_div(tmp, 1000000000LL);
    +-			tmp = div_s64(tmp, 1000000000LL);
     -			*val = tmp;
     -			return ret;
     -		default:
    @@ include/linux/iio/afe/rescale.h (new)
     +#ifndef __IIO_RESCALE_H__
     +#define __IIO_RESCALE_H__
     +
    ++#include <linux/types.h>
     +#include <linux/iio/iio.h>
     +
    ++struct device;
     +struct rescale;
     +
     +struct rescale_cfg {
 5:  8e63c4036157 !  7:  865296d2bc4f iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support
    @@ Commit message
         Some ADCs use IIO_VAL_INT_PLUS_{NANO,MICRO} scale types.
         Add support for these to allow using the iio-rescaler with them.
     
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## drivers/iio/afe/iio-rescale.c ##
     @@
    @@ drivers/iio/afe/iio-rescale.c
      #include <linux/property.h>
     +#include <linux/units.h>
      
    - int rescale_process_scale(struct rescale *rescale, int scale_type,
    + #include <linux/iio/afe/rescale.h>
    + #include <linux/iio/consumer.h>
    +@@ drivers/iio/afe/iio-rescale.c: int rescale_process_scale(struct rescale *rescale, int scale_type,
      			  int *val, int *val2)
      {
    - 	unsigned long long tmp;
    + 	s64 tmp;
     +	s32 rem;
     +	u32 mult;
     +	u32 neg;
    @@ drivers/iio/afe/iio-rescale.c
      	case IIO_VAL_FRACTIONAL:
     @@ drivers/iio/afe/iio-rescale.c: int rescale_process_scale(struct rescale *rescale, int scale_type,
      		tmp *= rescale->numerator;
    - 		do_div(tmp, 1000000000LL);
    + 		tmp = div_s64(tmp, 1000000000LL);
      		*val = tmp;
     +		return scale_type;
     +	case IIO_VAL_INT_PLUS_NANO:
     +	case IIO_VAL_INT_PLUS_MICRO:
    -+		mult = scale_type == IIO_VAL_INT_PLUS_NANO ? NANO : MICRO;
    ++		mult = scale_type == IIO_VAL_INT_PLUS_NANO ? GIGA : MEGA;
     +
     +		/*
     +		 * For IIO_VAL_INT_PLUS_{MICRO,NANO} scale types if either *val
 6:  eea57faec241 !  8:  aea3159ed169 iio: afe: rescale: add offset support
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: afe: rescale: add offset support
    @@ Commit message
         This is a preparatory change required for the addition of temperature
         sensing front ends.
     
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## drivers/iio/afe/iio-rescale.c ##
     @@ drivers/iio/afe/iio-rescale.c: int rescale_process_scale(struct rescale *rescale, int scale_type,
    @@ drivers/iio/afe/iio-rescale.c: int rescale_process_scale(struct rescale *rescale
     +		*val = div_s64(tmp, scale) + schan_off;
     +		return IIO_VAL_INT;
     +	case IIO_VAL_INT_PLUS_NANO:
    -+		tmp = (s64)rescale->offset * NANO;
    -+		tmp2 = ((s64)scale * NANO) + scale2;
    ++		tmp = (s64)rescale->offset * GIGA;
    ++		tmp2 = ((s64)scale * GIGA) + scale2;
     +		*val = div64_s64(tmp, tmp2) + schan_off;
     +		return IIO_VAL_INT;
     +	case IIO_VAL_INT_PLUS_MICRO:
    -+		tmp = (s64)rescale->offset * MICRO;
    -+		tmp2 = ((s64)scale * MICRO) + scale2;
    ++		tmp = (s64)rescale->offset * MEGA;
    ++		tmp2 = ((s64)scale * MEGA) + scale2;
     +		*val = div64_s64(tmp, tmp2) + schan_off;
     +		return IIO_VAL_INT;
     +	default:
 7:  6bc5dd8c92ac <  -:  ------------ iio: afe: rescale: use s64 for temporary scale calculations
 8:  7d426d67a7fd !  9:  7b518cba1cb5 iio: afe: rescale: fix accuracy for small fractional scales
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: afe: rescale: fix accuracy for small fractional scales
    @@ Commit message
         integer part. Switch to an IIO_VAL_INT_PLUS_NANO scale type in such
         cases to maintain accuracy.
     
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## drivers/iio/afe/iio-rescale.c ##
     @@ drivers/iio/afe/iio-rescale.c: int rescale_process_scale(struct rescale *rescale, int scale_type,
    @@ drivers/iio/afe/iio-rescale.c: int rescale_process_scale(struct rescale *rescale
     +		return IIO_VAL_INT_PLUS_NANO;
      	case IIO_VAL_INT_PLUS_NANO:
      	case IIO_VAL_INT_PLUS_MICRO:
    - 		mult = scale_type == IIO_VAL_INT_PLUS_NANO ? NANO : MICRO;
    + 		mult = scale_type == IIO_VAL_INT_PLUS_NANO ? GIGA : MEGA;
 9:  dbea6ae8fec2 ! 10:  4310bb2153e2 iio: afe: rescale: reduce risk of integer overflow
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: afe: rescale: reduce risk of integer overflow
    @@ Commit message
         a 64-bit integer. Since the rescaling is only performed on *val, reuse
         the IIO_VAL_FRACTIONAL_LOG2 case.
     
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## drivers/iio/afe/iio-rescale.c ##
     @@ drivers/iio/afe/iio-rescale.c: int rescale_process_scale(struct rescale *rescale, int scale_type,
    @@ drivers/iio/afe/iio-rescale.c: int rescale_process_scale(struct rescale *rescale
     +		if (scale_type == IIO_VAL_FRACTIONAL)
     +			tmp = *val2;
     +		else
    -+			tmp = 1 << *val2;
    ++			tmp = ULL(1) << *val2;
      
      		rem2 = *val % (int)tmp;
      		*val = *val / (int)tmp;
10:  9ab1138449d3 ! 11:  fd794683186a iio: afe: rescale: make use of units.h
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: afe: rescale: make use of units.h
     
         Make use of well-defined SI metric prefixes to improve code readability.
     
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
     
      ## drivers/iio/afe/iio-rescale.c ##
     @@ drivers/iio/afe/iio-rescale.c: int rescale_process_scale(struct rescale *rescale, int scale_type,
    @@ drivers/iio/afe/iio-rescale.c: int rescale_process_scale(struct rescale *rescale
      		fallthrough;
      	case IIO_VAL_FRACTIONAL_LOG2:
     -		tmp = (s64)*val * 1000000000LL;
    -+		tmp = (s64)*val * NANO;
    ++		tmp = (s64)*val * GIGA;
      		tmp = div_s64(tmp, rescale->denominator);
      		tmp *= rescale->numerator;
      
     -		tmp = div_s64_rem(tmp, 1000000000LL, &rem);
    -+		tmp = div_s64_rem(tmp, NANO, &rem);
    ++		tmp = div_s64_rem(tmp, GIGA, &rem);
      		*val = tmp;
      
      		if (!rem)
    @@ drivers/iio/afe/iio-rescale.c: int rescale_process_scale(struct rescale *rescale
      		*val2 = rem / (int)tmp;
      		if (rem2)
     -			*val2 += div_s64((s64)rem2 * 1000000000LL, tmp);
    -+			*val2 += div_s64((s64)rem2 * NANO, tmp);
    ++			*val2 += div_s64((s64)rem2 * GIGA, tmp);
      
      		return IIO_VAL_INT_PLUS_NANO;
      	case IIO_VAL_INT_PLUS_NANO:
    @@ drivers/iio/afe/iio-rescale.c: static int rescale_current_sense_amplifier_props(
      	 */
     -	factor = gcd(sense, 1000000);
     -	rescale->numerator = 1000000 / factor;
    -+	factor = gcd(sense, MICRO);
    -+	rescale->numerator = MICRO / factor;
    ++	factor = gcd(sense, MEGA);
    ++	rescale->numerator = MEGA / factor;
      	rescale->denominator = sense / factor;
      
      	factor = gcd(rescale->numerator, gain_mult);
    @@ drivers/iio/afe/iio-rescale.c: static int rescale_current_sense_shunt_props(stru
      
     -	factor = gcd(shunt, 1000000);
     -	rescale->numerator = 1000000 / factor;
    -+	factor = gcd(shunt, MICRO);
    -+	rescale->numerator = MICRO / factor;
    ++	factor = gcd(shunt, MEGA);
    ++	rescale->numerator = MEGA / factor;
      	rescale->denominator = shunt / factor;
      
      	return 0;
11:  3006151cd193 ! 12:  5053bcff8445 iio: test: add basic tests for the iio-rescale driver
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: test: add basic tests for the iio-rescale driver
    @@ Commit message
         Then run:
                 $ ./tools/testing/kunit/kunit.py run --kunitconfig .kunitconfig
     
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## drivers/iio/test/Kconfig ##
     @@
    @@ drivers/iio/test/iio-test-rescale.c (new)
     + * Copyright (c) 2021 Liam Beguin <liambeguin@gmail.com>
     + */
     +
    -+#include <kunit/test.h>
     +#include <linux/gcd.h>
    ++#include <linux/overflow.h>
    ++#include <linux/units.h>
    ++
     +#include <linux/iio/afe/rescale.h>
     +#include <linux/iio/iio.h>
    -+#include <linux/overflow.h>
    ++
    ++#include <kunit/test.h>
     +
     +struct rescale_tc_data {
     +	const char *name;
    @@ drivers/iio/test/iio-test-rescale.c (new)
     + */
     +static int iio_str_to_nano(const char *str, s64 *nano)
     +{
    -+	int fract_mult = 100000000LL;
     +	int tmp, tmp2;
     +	int ret = 0;
     +
    -+	ret = iio_str_to_fixpoint(str, fract_mult, &tmp, &tmp2);
    ++	/*
    ++	 * iio_str_to_fixpoint() uses 10^8 here instead of 10^9 as fract_mult is
    ++	 * the multiplier for the first decimal place.
    ++	 */
    ++	ret = iio_str_to_fixpoint(str, 100000000, &tmp, &tmp2);
     +	if (ret < 0)
     +		return ret;
     +
     +	if (tmp < 0)
     +		tmp2 *= -1;
     +
    -+	*nano = (s64)tmp * 10 * fract_mult + tmp2;
    ++	*nano = (s64)tmp * GIGA + tmp2;
     +
     +	return ret;
     +}
    @@ drivers/iio/test/iio-test-rescale.c (new)
     +		return -EINVAL;
     +	}
     +
    -+	err = 1000000 * abs(exp - real);
    -+	err = div64_u64(err, abs(exp));
    -+	return (int)err;
    ++	err = MEGA * abs(exp - real);
    ++
    ++	return (int)div64_u64(err, abs(exp));
     +}
     +
     +static void iio_rescale_test_scale(struct kunit *test)
12:  d4229e8d7f24 ! 13:  aec4f7e44277 iio: afe: rescale: add RTD temperature sensor support
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: afe: rescale: add RTD temperature sensor support
    @@ Commit message
         give range (usually 0 to 100 degrees Celsius). Common types of RTDs
         include PT100, PT500, and PT1000.
     
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## drivers/iio/afe/iio-rescale.c ##
     @@ drivers/iio/afe/iio-rescale.c: static int rescale_voltage_divider_props(struct device *dev,
    @@ drivers/iio/afe/iio-rescale.c: static int rescale_voltage_divider_props(struct d
     +		return ret;
     +	}
     +
    -+	tmp = r0 * iexc * alpha / MICRO;
    -+	factor = gcd(tmp, MICRO);
    -+	rescale->numerator = MICRO / factor;
    ++	tmp = r0 * iexc * alpha / MEGA;
    ++	factor = gcd(tmp, MEGA);
    ++	rescale->numerator = MEGA / factor;
     +	rescale->denominator = tmp / factor;
     +
    -+	rescale->offset = -1 * ((r0 * iexc) / MICRO * MILLI);
    ++	rescale->offset = -1 * ((r0 * iexc) / MEGA * MILLI);
     +
     +	return 0;
     +}
13:  b93e303c5e60 ! 14:  e5467185f3b3 iio: afe: rescale: add temperature transducers
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         iio: afe: rescale: add temperature transducers
     
         A temperature transducer is a device that converts a thermal quantity
    -    into any other physical quantity. This patch add support for temperature
    -    to voltage (like the LTC2997) and temperature to current (like the
    -    AD590) linear transducers.
    +    into any other physical quantity. This patch adds support for
    +    temperature to voltage (like the LTC2997) and temperature to current
    +    (like the AD590) linear transducers.
         In both cases these are assumed to be connected to a voltage ADC.
     
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## drivers/iio/afe/iio-rescale.c ##
     @@ drivers/iio/afe/iio-rescale.c: static int rescale_temp_sense_rtd_props(struct device *dev,
    @@ drivers/iio/afe/iio-rescale.c: static int rescale_temp_sense_rtd_props(struct de
     +		return ret;
     +	}
     +
    -+	rescale->numerator = MICRO;
    ++	rescale->numerator = MEGA;
     +	rescale->denominator = alpha * sense;
     +
     +	rescale->offset = div_s64((s64)offset * rescale->denominator,
14:  7bdd57435c5c ! 15:  3d16dc359e35 dt-bindings: iio: afe: add bindings for temperature-sense-rtd
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         dt-bindings: iio: afe: add bindings for temperature-sense-rtd
    @@ Commit message
         binding describe one case, the measurement of a temperature through the
         voltage across an RTD resistor such as a PT1000.
     
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
         Reviewed-by: Rob Herring <robh@kernel.org>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml (new) ##
     @@
15:  604ef3e42c07 ! 16:  b70fb25c3643 dt-bindings: iio: afe: add bindings for temperature transducers
    @@
      ## Metadata ##
    -Author: Liam Beguin <lvb@xiphos.com>
    +Author: Liam Beguin <liambeguin@gmail.com>
     
      ## Commit message ##
         dt-bindings: iio: afe: add bindings for temperature transducers
    @@ Commit message
         This binding describe one case, the measurement of a temperature
         through a temperature transducer (either voltage or current).
     
    -    Signed-off-by: Liam Beguin <lvb@xiphos.com>
    +    Signed-off-by: Liam Beguin <liambeguin@gmail.com>
         Reviewed-by: Rob Herring <robh@kernel.org>
    +    Reviewed-by: Peter Rosin <peda@axentia.se>
     
      ## Documentation/devicetree/bindings/iio/afe/temperature-transducer.yaml (new) ##
     @@

base-commit: 2b6bff0b122785f09cfbdc34b1aa9edceea6e4c1
-- 
2.34.0

[PATCH v12 01/16] iio: inkern: apply consumer scale on IIO_VAL_INT cases

[Liam Beguin]

When a consumer calls iio_read_channel_processed() and the channel has
an integer scale, the scale channel scale is applied and the processed
value is returned as expected.

On the other hand, if the consumer calls iio_convert_raw_to_processed()
the scaling factor requested by the consumer is not applied.

This for example causes the consumer to process mV when expecting uV.
Make sure to always apply the scaling factor requested by the consumer.

Fixes: 48e44ce0f881 ("iio:inkern: Add function to read the processed value")
Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/inkern.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index 0222885b334c..021e1397ffc5 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -616,7 +616,7 @@ static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
 
 	switch (scale_type) {
 	case IIO_VAL_INT:
-		*processed = raw64 * scale_val;
+		*processed = raw64 * scale_val * scale;
 		break;
 	case IIO_VAL_INT_PLUS_MICRO:
 		if (scale_val2 < 0)
-- 
2.34.0

[PATCH v12 02/16] iio: inkern: apply consumer scale when no channel scale is available

[Liam Beguin]

When a consumer calls iio_read_channel_processed() and no channel scale
is available, it's assumed that the scale is one and the raw value is
returned as expected.

On the other hand, if the consumer calls iio_convert_raw_to_processed()
the scaling factor requested by the consumer is not applied.

This for example causes the consumer to process mV when expecting uV.
Make sure to always apply the scaling factor requested by the consumer.

Fixes: adc8ec5ff183 ("iio: inkern: pass through raw values if no scaling")
Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/inkern.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index 021e1397ffc5..dbe13fad3cbb 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -607,10 +607,10 @@ static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
 					IIO_CHAN_INFO_SCALE);
 	if (scale_type < 0) {
 		/*
-		 * Just pass raw values as processed if no scaling is
-		 * available.
+		 * If no channel scaling is available apply consumer scale to
+		 * raw value and return.
 		 */
-		*processed = raw;
+		*processed = raw * scale;
 		return 0;
 	}
 
-- 
2.34.0

[PATCH v12 03/16] iio: inkern: make a best effort on offset calculation

[Liam Beguin]

iio_convert_raw_to_processed_unlocked() assumes the offset is an
integer. Make a best effort to get a valid offset value for fractional
cases without breaking implicit truncations.

Fixes: 48e44ce0f881 ("iio:inkern: Add function to read the processed value")
Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/inkern.c | 32 +++++++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index dbe13fad3cbb..df74765d33dc 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -595,13 +595,35 @@ EXPORT_SYMBOL_GPL(iio_read_channel_average_raw);
 static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
 	int raw, int *processed, unsigned int scale)
 {
-	int scale_type, scale_val, scale_val2, offset;
+	int scale_type, scale_val, scale_val2;
+	int offset_type, offset_val, offset_val2;
 	s64 raw64 = raw;
-	int ret;
 
-	ret = iio_channel_read(chan, &offset, NULL, IIO_CHAN_INFO_OFFSET);
-	if (ret >= 0)
-		raw64 += offset;
+	offset_type = iio_channel_read(chan, &offset_val, &offset_val2,
+				       IIO_CHAN_INFO_OFFSET);
+	if (offset_type >= 0) {
+		switch (offset_type) {
+		case IIO_VAL_INT:
+			break;
+		case IIO_VAL_INT_PLUS_MICRO:
+		case IIO_VAL_INT_PLUS_NANO:
+			/*
+			 * Both IIO_VAL_INT_PLUS_MICRO and IIO_VAL_INT_PLUS_NANO
+			 * implicitely truncate the offset to it's integer form.
+			 */
+			break;
+		case IIO_VAL_FRACTIONAL:
+			offset_val /= offset_val2;
+			break;
+		case IIO_VAL_FRACTIONAL_LOG2:
+			offset_val >>= offset_val2;
+			break;
+		default:
+			return -EINVAL;
+		}
+
+		raw64 += offset_val;
+	}
 
 	scale_type = iio_channel_read(chan, &scale_val, &scale_val2,
 					IIO_CHAN_INFO_SCALE);
-- 
2.34.0

[PATCH v12 04/16] iio: afe: rescale: use s64 for temporary scale calculations

[Liam Beguin]

All four scaling coefficients can take signed values.
Make tmp a signed 64-bit integer and switch to div_s64() to preserve
signs during 64-bit divisions.

Fixes: 8b74816b5a9a ("iio: afe: rescale: new driver")
Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/afe/iio-rescale.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 774eb3044edd..271d73e420c4 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -39,7 +39,7 @@ static int rescale_read_raw(struct iio_dev *indio_dev,
 			    int *val, int *val2, long mask)
 {
 	struct rescale *rescale = iio_priv(indio_dev);
-	unsigned long long tmp;
+	s64 tmp;
 	int ret;
 
 	switch (mask) {
@@ -77,10 +77,10 @@ static int rescale_read_raw(struct iio_dev *indio_dev,
 			*val2 = rescale->denominator;
 			return IIO_VAL_FRACTIONAL;
 		case IIO_VAL_FRACTIONAL_LOG2:
-			tmp = *val * 1000000000LL;
-			do_div(tmp, rescale->denominator);
+			tmp = (s64)*val * 1000000000LL;
+			tmp = div_s64(tmp, rescale->denominator);
 			tmp *= rescale->numerator;
-			do_div(tmp, 1000000000LL);
+			tmp = div_s64(tmp, 1000000000LL);
 			*val = tmp;
 			return ret;
 		default:
-- 
2.34.0

[PATCH v12 05/16] iio: afe: rescale: reorder includes

[Liam Beguin]

Includes should be ordered alphabetically which is already the case,
but follow what is done in other drivers by separation IIO specific
headers with a blank line.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
---
 drivers/iio/afe/iio-rescale.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 271d73e420c4..69710c481376 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -9,14 +9,15 @@
 
 #include <linux/err.h>
 #include <linux/gcd.h>
-#include <linux/iio/consumer.h>
-#include <linux/iio/iio.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/property.h>
 
+#include <linux/iio/consumer.h>
+#include <linux/iio/iio.h>
+
 struct rescale;
 
 struct rescale_cfg {
-- 
2.34.0

[PATCH v12 06/16] iio: afe: rescale: expose scale processing function

[Liam Beguin]

In preparation for the addition of kunit tests, expose the logic
responsible for combining channel scales.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/afe/iio-rescale.c   | 65 ++++++++++++++-------------------
 include/linux/iio/afe/rescale.h | 32 ++++++++++++++++
 2 files changed, 60 insertions(+), 37 deletions(-)
 create mode 100644 include/linux/iio/afe/rescale.h

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 69710c481376..65832dd09249 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -15,32 +15,43 @@
 #include <linux/platform_device.h>
 #include <linux/property.h>
 
+#include <linux/iio/afe/rescale.h>
 #include <linux/iio/consumer.h>
 #include <linux/iio/iio.h>
 
-struct rescale;
-
-struct rescale_cfg {
-	enum iio_chan_type type;
-	int (*props)(struct device *dev, struct rescale *rescale);
-};
+int rescale_process_scale(struct rescale *rescale, int scale_type,
+			  int *val, int *val2)
+{
+	s64 tmp;
 
-struct rescale {
-	const struct rescale_cfg *cfg;
-	struct iio_channel *source;
-	struct iio_chan_spec chan;
-	struct iio_chan_spec_ext_info *ext_info;
-	bool chan_processed;
-	s32 numerator;
-	s32 denominator;
-};
+	switch (scale_type) {
+	case IIO_VAL_FRACTIONAL:
+		*val *= rescale->numerator;
+		*val2 *= rescale->denominator;
+		return scale_type;
+	case IIO_VAL_INT:
+		*val *= rescale->numerator;
+		if (rescale->denominator == 1)
+			return scale_type;
+		*val2 = rescale->denominator;
+		return IIO_VAL_FRACTIONAL;
+	case IIO_VAL_FRACTIONAL_LOG2:
+		tmp = (s64)*val * 1000000000LL;
+		tmp = div_s64(tmp, rescale->denominator);
+		tmp *= rescale->numerator;
+		tmp = div_s64(tmp, 1000000000LL);
+		*val = tmp;
+		return scale_type;
+	default:
+		return -EOPNOTSUPP;
+	}
+}
 
 static int rescale_read_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan,
 			    int *val, int *val2, long mask)
 {
 	struct rescale *rescale = iio_priv(indio_dev);
-	s64 tmp;
 	int ret;
 
 	switch (mask) {
@@ -66,27 +77,7 @@ static int rescale_read_raw(struct iio_dev *indio_dev,
 		} else {
 			ret = iio_read_channel_scale(rescale->source, val, val2);
 		}
-		switch (ret) {
-		case IIO_VAL_FRACTIONAL:
-			*val *= rescale->numerator;
-			*val2 *= rescale->denominator;
-			return ret;
-		case IIO_VAL_INT:
-			*val *= rescale->numerator;
-			if (rescale->denominator == 1)
-				return ret;
-			*val2 = rescale->denominator;
-			return IIO_VAL_FRACTIONAL;
-		case IIO_VAL_FRACTIONAL_LOG2:
-			tmp = (s64)*val * 1000000000LL;
-			tmp = div_s64(tmp, rescale->denominator);
-			tmp *= rescale->numerator;
-			tmp = div_s64(tmp, 1000000000LL);
-			*val = tmp;
-			return ret;
-		default:
-			return -EOPNOTSUPP;
-		}
+		return rescale_process_scale(rescale, ret, val, val2);
 	default:
 		return -EINVAL;
 	}
diff --git a/include/linux/iio/afe/rescale.h b/include/linux/iio/afe/rescale.h
new file mode 100644
index 000000000000..698092b6cbb1
--- /dev/null
+++ b/include/linux/iio/afe/rescale.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 Liam Beguin <liambeguin@gmail.com>
+ */
+
+#ifndef __IIO_RESCALE_H__
+#define __IIO_RESCALE_H__
+
+#include <linux/types.h>
+#include <linux/iio/iio.h>
+
+struct device;
+struct rescale;
+
+struct rescale_cfg {
+	enum iio_chan_type type;
+	int (*props)(struct device *dev, struct rescale *rescale);
+};
+
+struct rescale {
+	const struct rescale_cfg *cfg;
+	struct iio_channel *source;
+	struct iio_chan_spec chan;
+	struct iio_chan_spec_ext_info *ext_info;
+	bool chan_processed;
+	s32 numerator;
+	s32 denominator;
+};
+
+int rescale_process_scale(struct rescale *rescale, int scale_type,
+			  int *val, int *val2);
+#endif /* __IIO_RESCALE_H__ */
-- 
2.34.0

[PATCH v12 07/16] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support

[Liam Beguin]

Some ADCs use IIO_VAL_INT_PLUS_{NANO,MICRO} scale types.
Add support for these to allow using the iio-rescaler with them.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/afe/iio-rescale.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 65832dd09249..f833eb38f8bb 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -14,6 +14,7 @@
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/property.h>
+#include <linux/units.h>
 
 #include <linux/iio/afe/rescale.h>
 #include <linux/iio/consumer.h>
@@ -23,6 +24,9 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 			  int *val, int *val2)
 {
 	s64 tmp;
+	s32 rem;
+	u32 mult;
+	u32 neg;
 
 	switch (scale_type) {
 	case IIO_VAL_FRACTIONAL:
@@ -41,6 +45,37 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 		tmp *= rescale->numerator;
 		tmp = div_s64(tmp, 1000000000LL);
 		*val = tmp;
+		return scale_type;
+	case IIO_VAL_INT_PLUS_NANO:
+	case IIO_VAL_INT_PLUS_MICRO:
+		mult = scale_type == IIO_VAL_INT_PLUS_NANO ? GIGA : MEGA;
+
+		/*
+		 * For IIO_VAL_INT_PLUS_{MICRO,NANO} scale types if either *val
+		 * OR *val2 is negative the schan scale is negative, i.e.
+		 * *val = 1 and *val2 = -0.5 yields -1.5 not -0.5.
+		 */
+		neg = *val < 0 || *val2 < 0;
+
+		tmp = (s64)abs(*val) * abs(rescale->numerator);
+		*val = div_s64_rem(tmp, abs(rescale->denominator), &rem);
+
+		tmp = (s64)rem * mult + (s64)abs(*val2) * abs(rescale->numerator);
+		tmp = div_s64(tmp, abs(rescale->denominator));
+
+		*val += div_s64_rem(tmp, mult, val2);
+
+		/*
+		 * If only one of the rescaler elements or the schan scale is
+		 * negative, the combined scale is negative.
+		 */
+		if (neg ^ ((rescale->numerator < 0) ^ (rescale->denominator < 0))) {
+			if (*val)
+				*val = -*val;
+			else
+				*val2 = -*val2;
+		}
+
 		return scale_type;
 	default:
 		return -EOPNOTSUPP;
-- 
2.34.0

[PATCH v12 08/16] iio: afe: rescale: add offset support

[Liam Beguin]

This is a preparatory change required for the addition of temperature
sensing front ends.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/afe/iio-rescale.c   | 80 +++++++++++++++++++++++++++++++++
 include/linux/iio/afe/rescale.h |  4 ++
 2 files changed, 84 insertions(+)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index f833eb38f8bb..68eb3e341939 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -82,11 +82,46 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 	}
 }
 
+int rescale_process_offset(struct rescale *rescale, int scale_type,
+			   int scale, int scale2, int schan_off,
+			   int *val, int *val2)
+{
+	s64 tmp, tmp2;
+
+	switch (scale_type) {
+	case IIO_VAL_FRACTIONAL:
+		tmp = (s64)rescale->offset * scale2;
+		*val = div_s64(tmp, scale) + schan_off;
+		return IIO_VAL_INT;
+	case IIO_VAL_INT:
+		*val = div_s64(rescale->offset, scale) + schan_off;
+		return IIO_VAL_INT;
+	case IIO_VAL_FRACTIONAL_LOG2:
+		tmp = (s64)rescale->offset * (1 << scale2);
+		*val = div_s64(tmp, scale) + schan_off;
+		return IIO_VAL_INT;
+	case IIO_VAL_INT_PLUS_NANO:
+		tmp = (s64)rescale->offset * GIGA;
+		tmp2 = ((s64)scale * GIGA) + scale2;
+		*val = div64_s64(tmp, tmp2) + schan_off;
+		return IIO_VAL_INT;
+	case IIO_VAL_INT_PLUS_MICRO:
+		tmp = (s64)rescale->offset * MEGA;
+		tmp2 = ((s64)scale * MEGA) + scale2;
+		*val = div64_s64(tmp, tmp2) + schan_off;
+		return IIO_VAL_INT;
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
 static int rescale_read_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan,
 			    int *val, int *val2, long mask)
 {
 	struct rescale *rescale = iio_priv(indio_dev);
+	int scale, scale2;
+	int schan_off = 0;
 	int ret;
 
 	switch (mask) {
@@ -113,6 +148,47 @@ static int rescale_read_raw(struct iio_dev *indio_dev,
 			ret = iio_read_channel_scale(rescale->source, val, val2);
 		}
 		return rescale_process_scale(rescale, ret, val, val2);
+	case IIO_CHAN_INFO_OFFSET:
+		/*
+		 * Processed channels are scaled 1-to-1 and source offset is
+		 * already taken into account.
+		 *
+		 * In other cases, real world measurement are expressed as:
+		 *
+		 *	schan_scale * (raw + schan_offset)
+		 *
+		 * Given that the rescaler parameters are applied recursively:
+		 *
+		 *	rescaler_scale * (schan_scale * (raw + schan_offset) +
+		 *		rescaler_offset)
+		 *
+		 * Or,
+		 *
+		 *	(rescaler_scale * schan_scale) * (raw +
+		 *		(schan_offset +	rescaler_offset / schan_scale)
+		 *
+		 * Thus, reusing the original expression the parameters exposed
+		 * to userspace are:
+		 *
+		 *	scale = schan_scale * rescaler_scale
+		 *	offset = schan_offset + rescaler_offset / schan_scale
+		 */
+		if (rescale->chan_processed) {
+			*val = rescale->offset;
+			return IIO_VAL_INT;
+		}
+
+		if (iio_channel_has_info(rescale->source->channel,
+					 IIO_CHAN_INFO_OFFSET)) {
+			ret = iio_read_channel_offset(rescale->source,
+						      &schan_off, NULL);
+			if (ret != IIO_VAL_INT)
+				return ret < 0 ? ret : -EOPNOTSUPP;
+		}
+
+		ret = iio_read_channel_scale(rescale->source, &scale, &scale2);
+		return rescale_process_offset(rescale, ret, scale, scale2,
+					      schan_off, val, val2);
 	default:
 		return -EINVAL;
 	}
@@ -189,6 +265,9 @@ static int rescale_configure_channel(struct device *dev,
 	chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
 		BIT(IIO_CHAN_INFO_SCALE);
 
+	if (rescale->offset)
+		chan->info_mask_separate |= BIT(IIO_CHAN_INFO_OFFSET);
+
 	/*
 	 * Using .read_avail() is fringe to begin with and makes no sense
 	 * whatsoever for processed channels, so we make sure that this cannot
@@ -353,6 +432,7 @@ static int rescale_probe(struct platform_device *pdev)
 	rescale->cfg = of_device_get_match_data(dev);
 	rescale->numerator = 1;
 	rescale->denominator = 1;
+	rescale->offset = 0;
 
 	ret = rescale->cfg->props(dev, rescale);
 	if (ret)
diff --git a/include/linux/iio/afe/rescale.h b/include/linux/iio/afe/rescale.h
index 698092b6cbb1..891bc935a396 100644
--- a/include/linux/iio/afe/rescale.h
+++ b/include/linux/iio/afe/rescale.h
@@ -25,8 +25,12 @@ struct rescale {
 	bool chan_processed;
 	s32 numerator;
 	s32 denominator;
+	s32 offset;
 };
 
 int rescale_process_scale(struct rescale *rescale, int scale_type,
 			  int *val, int *val2);
+int rescale_process_offset(struct rescale *rescale, int scale_type,
+			   int scale, int scale2, int schan_off,
+			   int *val, int *val2);
 #endif /* __IIO_RESCALE_H__ */
-- 
2.34.0

[PATCH v12 09/16] iio: afe: rescale: fix accuracy for small fractional scales

[Liam Beguin]

The approximation caused by integer divisions can be costly on smaller
scale values since the decimal part is significant compared to the
integer part. Switch to an IIO_VAL_INT_PLUS_NANO scale type in such
cases to maintain accuracy.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/afe/iio-rescale.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 68eb3e341939..ed3ef994997f 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -24,7 +24,7 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 			  int *val, int *val2)
 {
 	s64 tmp;
-	s32 rem;
+	s32 rem, rem2;
 	u32 mult;
 	u32 neg;
 
@@ -43,9 +43,23 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 		tmp = (s64)*val * 1000000000LL;
 		tmp = div_s64(tmp, rescale->denominator);
 		tmp *= rescale->numerator;
-		tmp = div_s64(tmp, 1000000000LL);
+
+		tmp = div_s64_rem(tmp, 1000000000LL, &rem);
 		*val = tmp;
-		return scale_type;
+
+		if (!rem)
+			return scale_type;
+
+		tmp = 1 << *val2;
+
+		rem2 = *val % (int)tmp;
+		*val = *val / (int)tmp;
+
+		*val2 = rem / (int)tmp;
+		if (rem2)
+			*val2 += div_s64((s64)rem2 * 1000000000LL, tmp);
+
+		return IIO_VAL_INT_PLUS_NANO;
 	case IIO_VAL_INT_PLUS_NANO:
 	case IIO_VAL_INT_PLUS_MICRO:
 		mult = scale_type == IIO_VAL_INT_PLUS_NANO ? GIGA : MEGA;
-- 
2.34.0

[PATCH v12 10/16] iio: afe: rescale: reduce risk of integer overflow

[Liam Beguin]

Reduce the risk of integer overflow by doing the scale calculation on
a 64-bit integer. Since the rescaling is only performed on *val, reuse
the IIO_VAL_FRACTIONAL_LOG2 case.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/afe/iio-rescale.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index ed3ef994997f..5b87965482d2 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -24,21 +24,31 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 			  int *val, int *val2)
 {
 	s64 tmp;
+	int _val, _val2;
 	s32 rem, rem2;
 	u32 mult;
 	u32 neg;
 
 	switch (scale_type) {
-	case IIO_VAL_FRACTIONAL:
-		*val *= rescale->numerator;
-		*val2 *= rescale->denominator;
-		return scale_type;
 	case IIO_VAL_INT:
 		*val *= rescale->numerator;
 		if (rescale->denominator == 1)
 			return scale_type;
 		*val2 = rescale->denominator;
 		return IIO_VAL_FRACTIONAL;
+	case IIO_VAL_FRACTIONAL:
+		/*
+		 * When the product of both scales doesn't overflow, avoid
+		 * potential accuracy loss (for in kernel consumers) by
+		 * keeping a fractional representation.
+		 */
+		if (!check_mul_overflow(*val, rescale->numerator, &_val) &&
+		    !check_mul_overflow(*val2, rescale->denominator, &_val2)) {
+			*val = _val;
+			*val2 = _val2;
+			return IIO_VAL_FRACTIONAL;
+		}
+		fallthrough;
 	case IIO_VAL_FRACTIONAL_LOG2:
 		tmp = (s64)*val * 1000000000LL;
 		tmp = div_s64(tmp, rescale->denominator);
@@ -50,7 +60,10 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 		if (!rem)
 			return scale_type;
 
-		tmp = 1 << *val2;
+		if (scale_type == IIO_VAL_FRACTIONAL)
+			tmp = *val2;
+		else
+			tmp = ULL(1) << *val2;
 
 		rem2 = *val % (int)tmp;
 		*val = *val / (int)tmp;
-- 
2.34.0

[PATCH v12 11/16] iio: afe: rescale: make use of units.h

[Liam Beguin]

Make use of well-defined SI metric prefixes to improve code readability.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
---
 drivers/iio/afe/iio-rescale.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 5b87965482d2..2379da74fe23 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -50,11 +50,11 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 		}
 		fallthrough;
 	case IIO_VAL_FRACTIONAL_LOG2:
-		tmp = (s64)*val * 1000000000LL;
+		tmp = (s64)*val * GIGA;
 		tmp = div_s64(tmp, rescale->denominator);
 		tmp *= rescale->numerator;
 
-		tmp = div_s64_rem(tmp, 1000000000LL, &rem);
+		tmp = div_s64_rem(tmp, GIGA, &rem);
 		*val = tmp;
 
 		if (!rem)
@@ -70,7 +70,7 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 
 		*val2 = rem / (int)tmp;
 		if (rem2)
-			*val2 += div_s64((s64)rem2 * 1000000000LL, tmp);
+			*val2 += div_s64((s64)rem2 * GIGA, tmp);
 
 		return IIO_VAL_INT_PLUS_NANO;
 	case IIO_VAL_INT_PLUS_NANO:
@@ -331,8 +331,8 @@ static int rescale_current_sense_amplifier_props(struct device *dev,
 	 * gain_div / (gain_mult * sense), while trying to keep the
 	 * numerator/denominator from overflowing.
 	 */
-	factor = gcd(sense, 1000000);
-	rescale->numerator = 1000000 / factor;
+	factor = gcd(sense, MEGA);
+	rescale->numerator = MEGA / factor;
 	rescale->denominator = sense / factor;
 
 	factor = gcd(rescale->numerator, gain_mult);
@@ -360,8 +360,8 @@ static int rescale_current_sense_shunt_props(struct device *dev,
 		return ret;
 	}
 
-	factor = gcd(shunt, 1000000);
-	rescale->numerator = 1000000 / factor;
+	factor = gcd(shunt, MEGA);
+	rescale->numerator = MEGA / factor;
 	rescale->denominator = shunt / factor;
 
 	return 0;
-- 
2.34.0

[PATCH v12 12/16] iio: test: add basic tests for the iio-rescale driver

[Liam Beguin]

The iio-rescale driver supports various combinations of scale types and
offsets. These can often result in large integer multiplications. Make
sure these calculations are done right by adding a set of kunit test
cases that build on top of iio-test-format.

To run these tests, add the following to .kunitconfig
	$ cat .kunitconfig
	CONFIG_IIO=y
	CONFIG_IIO_RESCALE_KUNIT_TEST=y
	CONFIG_KUNIT=y

Then run:
	$ ./tools/testing/kunit/kunit.py run --kunitconfig .kunitconfig

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/test/Kconfig            |  10 +
 drivers/iio/test/Makefile           |   1 +
 drivers/iio/test/iio-test-rescale.c | 711 ++++++++++++++++++++++++++++
 3 files changed, 722 insertions(+)
 create mode 100644 drivers/iio/test/iio-test-rescale.c

diff --git a/drivers/iio/test/Kconfig b/drivers/iio/test/Kconfig
index 679a7794af20..872ed4ed140a 100644
--- a/drivers/iio/test/Kconfig
+++ b/drivers/iio/test/Kconfig
@@ -4,6 +4,16 @@
 #
 
 # Keep in alphabetical order
+config IIO_RESCALE_KUNIT_TEST
+	bool "Test IIO rescale conversion functions"
+	depends on KUNIT && !IIO_RESCALE
+	default KUNIT_ALL_TESTS
+	help
+	  If you want to run tests on the iio-rescale code say Y here.
+
+	  This takes advantage of ARCH=um to run tests and should be used by
+	  developers to tests their changes to the rescaling logic.
+
 config IIO_TEST_FORMAT
         bool "Test IIO formatting functions"
         depends on KUNIT=y
diff --git a/drivers/iio/test/Makefile b/drivers/iio/test/Makefile
index 467519a2027e..f15ae0a6394f 100644
--- a/drivers/iio/test/Makefile
+++ b/drivers/iio/test/Makefile
@@ -4,5 +4,6 @@
 #
 
 # Keep in alphabetical order
+obj-$(CONFIG_IIO_RESCALE_KUNIT_TEST) += iio-test-rescale.o ../afe/iio-rescale.o
 obj-$(CONFIG_IIO_TEST_FORMAT) += iio-test-format.o
 CFLAGS_iio-test-format.o += $(DISABLE_STRUCTLEAK_PLUGIN)
diff --git a/drivers/iio/test/iio-test-rescale.c b/drivers/iio/test/iio-test-rescale.c
new file mode 100644
index 000000000000..a3bbe2db76d3
--- /dev/null
+++ b/drivers/iio/test/iio-test-rescale.c
@@ -0,0 +1,711 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Kunit tests for IIO rescale conversions
+ *
+ * Copyright (c) 2021 Liam Beguin <liambeguin@gmail.com>
+ */
+
+#include <linux/gcd.h>
+#include <linux/overflow.h>
+#include <linux/units.h>
+
+#include <linux/iio/afe/rescale.h>
+#include <linux/iio/iio.h>
+
+#include <kunit/test.h>
+
+struct rescale_tc_data {
+	const char *name;
+
+	const s32 numerator;
+	const s32 denominator;
+	const s32 offset;
+
+	const int schan_val;
+	const int schan_val2;
+	const int schan_off;
+	const int schan_scale_type;
+
+	const char *expected;
+	const char *expected_off;
+};
+
+const struct rescale_tc_data scale_cases[] = {
+	/*
+	 * Typical use cases
+	 */
+	{
+		.name = "typical IIO_VAL_INT, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT,
+		.schan_val = 42,
+		.expected = "5210.918114143",
+	},
+	{
+		.name = "typical IIO_VAL_INT, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT,
+		.schan_val = 42,
+		.expected = "-5210.918114143",
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 42,
+		.schan_val2 = 20,
+		.expected = "260.545905707",
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 42,
+		.schan_val2 = 20,
+		.expected = "-260.545905707",
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL_LOG2, positive",
+		.numerator = 42,
+		.denominator = 53,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 4096,
+		.schan_val2 = 16,
+		.expected = "0.049528301",
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL_LOG2, negative",
+		.numerator = -42,
+		.denominator = 53,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 4096,
+		.schan_val2 = 16,
+		.expected = "-0.049528301",
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_NANO, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456,
+		.expected = "1240.710106203",
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_NANO, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456,
+		.expected = "-1240.710106203",
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_MICRO, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 1234,
+		.expected = "1240.84789",
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_MICRO, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 1234,
+		.expected = "-1240.84789",
+	},
+	/*
+	 * Use cases with small scales involving divisions
+	 */
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 261/509 scaled by 90/1373754273",
+		.numerator = 261,
+		.denominator = 509,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 90,
+		.schan_val2 = 1373754273,
+		.expected = "0.000000033594",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 90/1373754273 scaled by 261/509",
+		.numerator = 90,
+		.denominator = 1373754273,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 261,
+		.schan_val2 = 509,
+		.expected = "0.000000033594",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 760/1373754273 scaled by 427/2727",
+		.numerator = 760,
+		.denominator = 1373754273,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 427,
+		.schan_val2 = 2727,
+		.expected = "0.000000086626",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 761/1373754273 scaled by 427/2727",
+		.numerator = 761,
+		.denominator = 1373754273,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 427,
+		.schan_val2 = 2727,
+		.expected = "0.000000086740",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 5/32768 scaled by 3/10000",
+		.numerator = 5,
+		.denominator = 32768,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 3,
+		.schan_val2 = 10000,
+		.expected = "0.0000000457763671875",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 0 < scale < 1",
+		.numerator = 6,
+		.denominator = 6,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 1,
+		.schan_val2 = 3,
+		.expected = "0.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, -1 < scale < 0",
+		.numerator = -6,
+		.denominator = 6,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 1,
+		.schan_val2 = 3,
+		.expected = "-0.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 0 < scale < 2",
+		.numerator = 8,
+		.denominator = 2,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 1,
+		.schan_val2 = 3,
+		.expected = "1.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, -2 < scale < 0",
+		.numerator = -8,
+		.denominator = 2,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 1,
+		.schan_val2 = 3,
+		.expected = "-1.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, 760/32768 scaled by 15/22",
+		.numerator = 760,
+		.denominator = 32768,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 15,
+		.schan_val2 = 22,
+		.expected = "0.000000082946",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, 761/32768 scaled by 15/22",
+		.numerator = 761,
+		.denominator = 32768,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 15,
+		.schan_val2 = 22,
+		.expected = "0.000000083055",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, 0 < scale < 1",
+		.numerator = 16,
+		.denominator = 3,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 1,
+		.schan_val2 = 4,
+		.expected = "0.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, -1 < scale < 0",
+		.numerator = -16,
+		.denominator = 3,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 1,
+		.schan_val2 = 4,
+		.expected = "-0.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, 0 < scale < 2",
+		.numerator = 8,
+		.denominator = 3,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 1,
+		.schan_val2 = 1,
+		.expected = "1.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, -2 < scale < 0",
+		.numerator = -8,
+		.denominator = 3,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 1,
+		.schan_val2 = 1,
+		.expected = "-1.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_INT_PLUS_MICRO, positive",
+		.numerator = 1,
+		.denominator = 2,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 5,
+		.schan_val2 = 1234,
+		.expected = "2.500617",
+	},
+	{
+		.name = "small IIO_VAL_INT_PLUS_MICRO, negative",
+		.numerator = -1,
+		.denominator = 2,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 5,
+		.schan_val2 = 1234,
+		.expected = "-2.500617",
+	},
+	/*
+	 * INT_PLUS_{MICRO,NANO} positive/negative corner cases
+	 */
+	{
+		.name = "negative IIO_VAL_INT_PLUS_NANO, negative schan",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = 123456,
+		.expected = "-1240.710106203",
+	},
+	{
+		.name = "negative IIO_VAL_INT_PLUS_NANO, both negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = 123456,
+		.expected = "1240.710106203",
+	},
+	{
+		.name = "negative IIO_VAL_INT_PLUS_NANO, 3 negative",
+		.numerator = -1000000,
+		.denominator = -8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = 123456,
+		.expected = "-1240.710106203",
+	},
+	{
+		.name = "negative IIO_VAL_INT_PLUS_NANO, 4 negative",
+		.numerator = -1000000,
+		.denominator = -8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = -123456,
+		.expected = "-1240.710106203",
+	},
+	{
+		.name = "negative IIO_VAL_INT_PLUS_NANO, negative, *val = 0",
+		.numerator = 1,
+		.denominator = -10,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 0,
+		.schan_val2 = 123456789,
+		.expected = "-0.012345678",
+	},
+	/*
+	 * INT_PLUS_{MICRO,NANO} decimal part overflow
+	 */
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_NANO, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.expected = "1256.01200856",
+	},
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_NANO, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.expected = "-1256.01200856",
+	},
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_NANO, negative schan",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = 123456789,
+		.expected = "-1256.01200856",
+	},
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_MICRO, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.expected = "16557.914267",
+	},
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_MICRO, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.expected = "-16557.914267",
+	},
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_MICRO, negative schan",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = -10,
+		.schan_val2 = 123456789,
+		.expected = "-16557.914267",
+	},
+	/*
+	 * 32-bit overflow conditions
+	 */
+	{
+		.name = "overflow IIO_VAL_FRACTIONAL, positive",
+		.numerator = 2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = S32_MAX,
+		.schan_val2 = 1,
+		.expected = "214748364.7",
+	},
+	{
+		.name = "overflow IIO_VAL_FRACTIONAL, negative",
+		.numerator = -2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = S32_MAX,
+		.schan_val2 = 1,
+		.expected = "-214748364.7",
+	},
+	{
+		.name = "overflow IIO_VAL_FRACTIONAL_LOG2, positive",
+		.numerator = S32_MAX,
+		.denominator = 4096,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 4096,
+		.schan_val2 = 16,
+		.expected = "32767.99998474121",
+	},
+	{
+		.name = "overflow IIO_VAL_FRACTIONAL_LOG2, negative",
+		.numerator = S32_MAX,
+		.denominator = 4096,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = -4096,
+		.schan_val2 = 16,
+		.expected = "-32767.99998474121",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_NANO, positive",
+		.numerator = 2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = S32_MAX,
+		.expected = "1.214748364",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_NANO, negative",
+		.numerator = -2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = S32_MAX,
+		.expected = "-1.214748364",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_NANO, negative schan",
+		.numerator = 2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = S32_MAX,
+		.expected = "-1.214748364",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_MICRO, positive",
+		.numerator = 2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = S32_MAX,
+		.expected = "215.748364",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_MICRO, negative",
+		.numerator = -2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = S32_MAX,
+		.expected = "-215.748364",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_MICRO, negative schan",
+		.numerator = 2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = -10,
+		.schan_val2 = S32_MAX,
+		.expected = "-215.748364",
+	},
+};
+
+const struct rescale_tc_data offset_cases[] = {
+	/*
+	 * Typical use cases
+	 */
+	{
+		.name = "typical IIO_VAL_INT, positive",
+		.offset = 1234,
+		.schan_scale_type = IIO_VAL_INT,
+		.schan_val = 123,
+		.schan_val2 = 0,
+		.schan_off = 14,
+		.expected_off = "24", /* 23.872 */
+	},
+	{
+		.name = "typical IIO_VAL_INT, negative",
+		.offset = -1234,
+		.schan_scale_type = IIO_VAL_INT,
+		.schan_val = 12,
+		.schan_val2 = 0,
+		.schan_off = 14,
+		.expected_off = "-88", /* -88.83333333333333 */
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL, positive",
+		.offset = 1234,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 12,
+		.schan_val2 = 34,
+		.schan_off = 14,
+		.expected_off = "3510", /* 3510.333333333333 */
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL, negative",
+		.offset = -1234,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 12,
+		.schan_val2 = 34,
+		.schan_off = 14,
+		.expected_off = "-3482", /* -3482.333333333333 */
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL_LOG2, positive",
+		.offset = 1234,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 12,
+		.schan_val2 = 16,
+		.schan_off = 14,
+		.expected_off = "6739299", /* 6739299.333333333 */
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL_LOG2, negative",
+		.offset = -1234,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 12,
+		.schan_val2 = 16,
+		.schan_off = 14,
+		.expected_off = "-6739271", /* -6739271.333333333 */
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_NANO, positive",
+		.offset = 1234,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.schan_off = 14,
+		.expected_off = "135", /* 135.8951219647469 */
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_NANO, negative",
+		.offset = -1234,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.schan_off = 14,
+		.expected_off = "-107", /* -107.89512196474689 */
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_MICRO, positive",
+		.offset = 1234,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.schan_off = 14,
+		.expected_off = "23", /* 23.246438560723952 */
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_MICRO, negative",
+		.offset = -12345,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.schan_off = 14,
+		.expected_off = "-78", /* -78.50185091745313 */
+	},
+};
+
+static void case_to_desc(const struct rescale_tc_data *t, char *desc)
+{
+	strcpy(desc, t->name);
+}
+
+KUNIT_ARRAY_PARAM(iio_rescale_scale, scale_cases, case_to_desc);
+KUNIT_ARRAY_PARAM(iio_rescale_offset, offset_cases, case_to_desc);
+
+/**
+ * iio_str_to_nano() - Parse a fixed-point string to get an
+ *                      IIO_VAL_INT_PLUS_NANO value
+ * @str: The string to parse
+ * @nano: The number as an integer
+ *
+ * Returns 0 on success, or a negative error code if the string cound not be
+ * parsed.
+ */
+static int iio_str_to_nano(const char *str, s64 *nano)
+{
+	int tmp, tmp2;
+	int ret = 0;
+
+	/*
+	 * iio_str_to_fixpoint() uses 10^8 here instead of 10^9 as fract_mult is
+	 * the multiplier for the first decimal place.
+	 */
+	ret = iio_str_to_fixpoint(str, 100000000, &tmp, &tmp2);
+	if (ret < 0)
+		return ret;
+
+	if (tmp < 0)
+		tmp2 *= -1;
+
+	*nano = (s64)tmp * GIGA + tmp2;
+
+	return ret;
+}
+
+/**
+ * iio_test_relative_error_ppm() - Compute relative error (in parts-per-million)
+ *                                 between two fixed-point strings
+ * @real_str: The real value as a string
+ * @exp_str: The expected value as a string
+ *
+ * Returns a negative error code if the strings cound not be parsed, or the
+ * relative error in parts-per-million.
+ */
+static int iio_test_relative_error_ppm(const char *real_str, const char *exp_str)
+{
+	s64 real, exp, err;
+	int ret;
+
+	ret = iio_str_to_nano(real_str, &real);
+	if (ret < 0)
+		return ret;
+
+	ret = iio_str_to_nano(exp_str, &exp);
+	if (ret < 0)
+		return ret;
+
+	if (!exp) {
+		pr_err("Expected value is null, relative error is undefined\n");
+		return -EINVAL;
+	}
+
+	err = MEGA * abs(exp - real);
+
+	return (int)div64_u64(err, abs(exp));
+}
+
+static void iio_rescale_test_scale(struct kunit *test)
+{
+	struct rescale_tc_data *t = (struct rescale_tc_data *)test->param_value;
+	char *buff = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	struct rescale rescale;
+	int values[2];
+	int rel_ppm;
+	int ret;
+
+	rescale.numerator = t->numerator;
+	rescale.denominator = t->denominator;
+	rescale.offset = t->offset;
+	values[0] = t->schan_val;
+	values[1] = t->schan_val2;
+
+	ret = rescale_process_scale(&rescale, t->schan_scale_type,
+				    &values[0], &values[1]);
+
+	ret = iio_format_value(buff, ret, 2, values);
+	KUNIT_EXPECT_EQ(test, (int)strlen(buff), ret);
+
+	rel_ppm = iio_test_relative_error_ppm(buff, t->expected);
+	KUNIT_EXPECT_GE_MSG(test, rel_ppm, 0, "failed to compute ppm\n");
+
+	KUNIT_EXPECT_EQ_MSG(test, rel_ppm, 0,
+			    "\t    real=%s"
+			    "\texpected=%s\n",
+			    buff, t->expected);
+}
+
+static void iio_rescale_test_offset(struct kunit *test)
+{
+	struct rescale_tc_data *t = (struct rescale_tc_data *)test->param_value;
+	char *buff_off = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	struct rescale rescale;
+	int values[2];
+	int ret;
+
+	rescale.numerator = t->numerator;
+	rescale.denominator = t->denominator;
+	rescale.offset = t->offset;
+	values[0] = t->schan_val;
+	values[1] = t->schan_val2;
+
+	ret = rescale_process_offset(&rescale, t->schan_scale_type,
+				     t->schan_val, t->schan_val2, t->schan_off,
+				     &values[0], &values[1]);
+
+	ret = iio_format_value(buff_off, ret, 2, values);
+	KUNIT_EXPECT_EQ(test, (int)strlen(buff_off), ret);
+
+	KUNIT_EXPECT_STREQ(test, strim(buff_off), t->expected_off);
+}
+
+static struct kunit_case iio_rescale_test_cases[] = {
+	KUNIT_CASE_PARAM(iio_rescale_test_scale, iio_rescale_scale_gen_params),
+	KUNIT_CASE_PARAM(iio_rescale_test_offset, iio_rescale_offset_gen_params),
+	{}
+};
+
+static struct kunit_suite iio_rescale_test_suite = {
+	.name = "iio-rescale",
+	.test_cases = iio_rescale_test_cases,
+};
+kunit_test_suite(iio_rescale_test_suite);
-- 
2.34.0

[PATCH v12 13/16] iio: afe: rescale: add RTD temperature sensor support

[Liam Beguin]

An RTD (Resistance Temperature Detector) is a kind of temperature
sensor used to get a linear voltage to temperature reading within a
give range (usually 0 to 100 degrees Celsius). Common types of RTDs
include PT100, PT500, and PT1000.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/afe/iio-rescale.c | 48 +++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 2379da74fe23..12c5e8d0d25c 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -394,10 +394,52 @@ static int rescale_voltage_divider_props(struct device *dev,
 	return 0;
 }
 
+static int rescale_temp_sense_rtd_props(struct device *dev,
+					struct rescale *rescale)
+{
+	u32 factor;
+	u32 alpha;
+	u32 iexc;
+	u32 tmp;
+	int ret;
+	u32 r0;
+
+	ret = device_property_read_u32(dev, "excitation-current-microamp",
+				       &iexc);
+	if (ret) {
+		dev_err(dev, "failed to read excitation-current-microamp: %d\n",
+			ret);
+		return ret;
+	}
+
+	ret = device_property_read_u32(dev, "alpha-ppm-per-celsius", &alpha);
+	if (ret) {
+		dev_err(dev, "failed to read alpha-ppm-per-celsius: %d\n",
+			ret);
+		return ret;
+	}
+
+	ret = device_property_read_u32(dev, "r-naught-ohms", &r0);
+	if (ret) {
+		dev_err(dev, "failed to read r-naught-ohms: %d\n", ret);
+		return ret;
+	}
+
+	tmp = r0 * iexc * alpha / MEGA;
+	factor = gcd(tmp, MEGA);
+	rescale->numerator = MEGA / factor;
+	rescale->denominator = tmp / factor;
+
+	rescale->offset = -1 * ((r0 * iexc) / MEGA * MILLI);
+
+	return 0;
+}
+
 enum rescale_variant {
 	CURRENT_SENSE_AMPLIFIER,
 	CURRENT_SENSE_SHUNT,
 	VOLTAGE_DIVIDER,
+	TEMP_SENSE_RTD,
 };
 
 static const struct rescale_cfg rescale_cfg[] = {
@@ -413,6 +455,10 @@ static const struct rescale_cfg rescale_cfg[] = {
 		.type = IIO_VOLTAGE,
 		.props = rescale_voltage_divider_props,
 	},
+	[TEMP_SENSE_RTD] = {
+		.type = IIO_TEMP,
+		.props = rescale_temp_sense_rtd_props,
+	},
 };
 
 static const struct of_device_id rescale_match[] = {
@@ -422,6 +468,8 @@ static const struct of_device_id rescale_match[] = {
 	  .data = &rescale_cfg[CURRENT_SENSE_SHUNT], },
 	{ .compatible = "voltage-divider",
 	  .data = &rescale_cfg[VOLTAGE_DIVIDER], },
+	{ .compatible = "temperature-sense-rtd",
+	  .data = &rescale_cfg[TEMP_SENSE_RTD], },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, rescale_match);
-- 
2.34.0

[PATCH v12 14/16] iio: afe: rescale: add temperature transducers

[Liam Beguin]

A temperature transducer is a device that converts a thermal quantity
into any other physical quantity. This patch adds support for
temperature to voltage (like the LTC2997) and temperature to current
(like the AD590) linear transducers.
In both cases these are assumed to be connected to a voltage ADC.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 drivers/iio/afe/iio-rescale.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 12c5e8d0d25c..4d70b72f59a5 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -435,11 +435,37 @@ static int rescale_temp_sense_rtd_props(struct device *dev,
 	return 0;
 }
 
+static int rescale_temp_transducer_props(struct device *dev,
+					 struct rescale *rescale)
+{
+	s32 offset = 0;
+	s32 sense = 1;
+	s32 alpha;
+	int ret;
+
+	device_property_read_u32(dev, "sense-offset-millicelsius", &offset);
+	device_property_read_u32(dev, "sense-resistor-ohms", &sense);
+	ret = device_property_read_u32(dev, "alpha-ppm-per-celsius", &alpha);
+	if (ret) {
+		dev_err(dev, "failed to read alpha-ppm-per-celsius: %d\n", ret);
+		return ret;
+	}
+
+	rescale->numerator = MEGA;
+	rescale->denominator = alpha * sense;
+
+	rescale->offset = div_s64((s64)offset * rescale->denominator,
+				  rescale->numerator);
+
+	return 0;
+}
+
 enum rescale_variant {
 	CURRENT_SENSE_AMPLIFIER,
 	CURRENT_SENSE_SHUNT,
 	VOLTAGE_DIVIDER,
 	TEMP_SENSE_RTD,
+	TEMP_TRANSDUCER,
 };
 
 static const struct rescale_cfg rescale_cfg[] = {
@@ -459,6 +485,10 @@ static const struct rescale_cfg rescale_cfg[] = {
 		.type = IIO_TEMP,
 		.props = rescale_temp_sense_rtd_props,
 	},
+	[TEMP_TRANSDUCER] = {
+		.type = IIO_TEMP,
+		.props = rescale_temp_transducer_props,
+	},
 };
 
 static const struct of_device_id rescale_match[] = {
@@ -470,6 +500,8 @@ static const struct of_device_id rescale_match[] = {
 	  .data = &rescale_cfg[VOLTAGE_DIVIDER], },
 	{ .compatible = "temperature-sense-rtd",
 	  .data = &rescale_cfg[TEMP_SENSE_RTD], },
+	{ .compatible = "temperature-transducer",
+	  .data = &rescale_cfg[TEMP_TRANSDUCER], },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, rescale_match);
-- 
2.34.0

[PATCH v12 15/16] dt-bindings: iio: afe: add bindings for temperature-sense-rtd

[Liam Beguin]

An ADC is often used to measure other quantities indirectly. This
binding describe one case, the measurement of a temperature through the
voltage across an RTD resistor such as a PT1000.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 .../iio/afe/temperature-sense-rtd.yaml        | 101 ++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml

diff --git a/Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml b/Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml
new file mode 100644
index 000000000000..336ce96371db
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml
@@ -0,0 +1,101 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/afe/temperature-sense-rtd.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Temperature Sense RTD
+
+maintainers:
+  - Liam Beguin <liambeguin@gmail.com>
+
+description: |
+  RTDs (Resistance Temperature Detectors) are a kind of temperature sensors
+  used to get a linear voltage to temperature reading within a give range
+  (usually 0 to 100 degrees Celsius).
+
+  When an io-channel measures the output voltage across an RTD such as a
+  PT1000, the interesting measurement is almost always the corresponding
+  temperature, not the voltage output. This binding describes such a circuit.
+
+  The general transfer function here is (using SI units)
+
+    V = R(T) * iexc
+    R(T) = r0 * (1 + alpha * T)
+    T = 1 / (alpha * r0 * iexc) * (V - r0 * iexc)
+
+  The following circuit matches what's in the examples section.
+
+           5V0
+          -----
+            |
+        +---+----+
+        |  R 5k  |
+        +---+----+
+            |
+            V 1mA
+            |
+            +---- Vout
+            |
+        +---+----+
+        | PT1000 |
+        +---+----+
+            |
+          -----
+           GND
+
+properties:
+  compatible:
+    const: temperature-sense-rtd
+
+  io-channels:
+    maxItems: 1
+    description: |
+      Channel node of a voltage io-channel.
+
+  '#io-channel-cells':
+    const: 0
+
+  excitation-current-microamp:
+    description: The current fed through the RTD sensor.
+
+  alpha-ppm-per-celsius:
+    description: |
+      alpha can also be expressed in micro-ohms per ohm Celsius. It's a linear
+      approximation of the resistance versus temperature relationship
+      between 0 and 100 degrees Celsius.
+
+      alpha = (R_100 - R_0) / (100 * R_0)
+
+      Where, R_100 is the resistance of the sensor at 100 degrees Celsius, and
+      R_0 (or r-naught-ohms) is the resistance of the sensor at 0 degrees
+      Celsius.
+
+      Pure platinum has an alpha of 3925. Industry standards such as IEC60751
+      and ASTM E-1137 specify an alpha of 3850.
+
+  r-naught-ohms:
+    description: |
+      Resistance of the sensor at 0 degrees Celsius.
+      Common values are 100 for PT100, 500 for PT500, and 1000 for PT1000
+
+additionalProperties: false
+required:
+  - compatible
+  - io-channels
+  - excitation-current-microamp
+  - alpha-ppm-per-celsius
+  - r-naught-ohms
+
+examples:
+  - |
+    pt1000_1: temperature-sensor0 {
+        compatible = "temperature-sense-rtd";
+        #io-channel-cells = <0>;
+        io-channels = <&temp_adc1 0>;
+
+        excitation-current-microamp = <1000>; /* i = U/R = 5 / 5000 */
+        alpha-ppm-per-celsius = <3908>;
+        r-naught-ohms = <1000>;
+    };
+...
-- 
2.34.0

[PATCH v12 16/16] dt-bindings: iio: afe: add bindings for temperature transducers

[Liam Beguin]

An ADC is often used to measure other quantities indirectly.
This binding describe one case, the measurement of a temperature
through a temperature transducer (either voltage or current).

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 .../iio/afe/temperature-transducer.yaml       | 114 ++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/afe/temperature-transducer.yaml

diff --git a/Documentation/devicetree/bindings/iio/afe/temperature-transducer.yaml b/Documentation/devicetree/bindings/iio/afe/temperature-transducer.yaml
new file mode 100644
index 000000000000..cfbf5350db27
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/afe/temperature-transducer.yaml
@@ -0,0 +1,114 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/afe/temperature-transducer.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Temperature Transducer
+
+maintainers:
+  - Liam Beguin <liambeguin@gmail.com>
+
+description: |
+  A temperature transducer is a device that converts a thermal quantity
+  into any other physical quantity. This binding applies to temperature to
+  voltage (like the LTC2997), and temperature to current (like the AD590)
+  linear transducers.
+  In both cases these are assumed to be connected to a voltage ADC.
+
+  When an io-channel measures the output voltage of a temperature analog front
+  end such as a temperature transducer, the interesting measurement is almost
+  always the corresponding temperature, not the voltage output. This binding
+  describes such a circuit.
+
+  The general transfer function here is (using SI units)
+    V(T) = Rsense * Isense(T)
+    T = (Isense(T) / alpha) + offset
+    T = 1 / (Rsense * alpha) * (V + offset * Rsense * alpha)
+
+  When using a temperature to voltage transducer, Rsense is set to 1.
+
+  The following circuits show a temperature to current and a temperature to
+  voltage transducer that can be used with this binding.
+
+           VCC
+          -----
+            |
+        +---+---+
+        | AD590 |                               VCC
+        +---+---+                              -----
+            |                                    |
+            V proportional to T             +----+----+
+            |                          D+ --+         |
+            +---- Vout                      | LTC2997 +--- Vout
+            |                          D- --+         |
+        +---+----+                          +---------+
+        | Rsense |                               |
+        +---+----+                             -----
+            |                                   GND
+          -----
+           GND
+
+properties:
+  compatible:
+    const: temperature-transducer
+
+  io-channels:
+    maxItems: 1
+    description: |
+      Channel node of a voltage io-channel.
+
+  '#io-channel-cells':
+    const: 0
+
+  sense-offset-millicelsius:
+    description: |
+      Temperature offset.
+      This offset is commonly used to convert from Kelvins to degrees Celsius.
+      In that case, sense-offset-millicelsius would be set to <(-273150)>.
+    default: 0
+
+  sense-resistor-ohms:
+    description: |
+      The sense resistor.
+      By default sense-resistor-ohms cancels out the resistor making the
+      circuit behave like a temperature transducer.
+    default: 1
+
+  alpha-ppm-per-celsius:
+    description: |
+      Sometimes referred to as output gain, slope, or temperature coefficient.
+
+      alpha is expressed in parts per million which can be micro-amps per
+      degrees Celsius or micro-volts per degrees Celsius. The is the main
+      characteristic of a temperature transducer and should be stated in the
+      datasheet.
+
+additionalProperties: false
+
+required:
+  - compatible
+  - io-channels
+  - alpha-ppm-per-celsius
+
+examples:
+  - |
+    ad950: temperature-sensor-0 {
+        compatible = "temperature-transducer";
+        #io-channel-cells = <0>;
+        io-channels = <&temp_adc 3>;
+
+        sense-offset-millicelsius = <(-273150)>; /* Kelvin to degrees Celsius */
+        sense-resistor-ohms = <8060>;
+        alpha-ppm-per-celsius = <1>; /* 1 uA/K */
+    };
+  - |
+    znq_tmp: temperature-sensor-1 {
+        compatible = "temperature-transducer";
+        #io-channel-cells = <0>;
+        io-channels = <&temp_adc 2>;
+
+        sense-offset-millicelsius = <(-273150)>; /* Kelvin to degrees Celsius */
+        alpha-ppm-per-celsius = <4000>; /* 4 mV/K */
+    };
+...
-- 
2.34.0

Re: [PATCH v12 07/16] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support

[Andy Shevchenko]

On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
>
> Some ADCs use IIO_VAL_INT_PLUS_{NANO,MICRO} scale types.
> Add support for these to allow using the iio-rescaler with them.

...

> +               mult = scale_type == IIO_VAL_INT_PLUS_NANO ? GIGA : MEGA;
> +
> +               /*
> +                * For IIO_VAL_INT_PLUS_{MICRO,NANO} scale types if either *val
> +                * OR *val2 is negative the schan scale is negative, i.e.
> +                * *val = 1 and *val2 = -0.5 yields -1.5 not -0.5.
> +                */
> +               neg = *val < 0 || *val2 < 0;
> +
> +               tmp = (s64)abs(*val) * abs(rescale->numerator);
> +               *val = div_s64_rem(tmp, abs(rescale->denominator), &rem);
> +
> +               tmp = (s64)rem * mult + (s64)abs(*val2) * abs(rescale->numerator);
> +               tmp = div_s64(tmp, abs(rescale->denominator));

Isn't it too many repetitive abs() calls?

What about

// Create a macro and use for u16 (struct rn5t618_channel_ratios), s16
(struct twl4030_prescale_divider_ratios), s32 (can be reused in struct
rescale)
struct u32_fract {
  u32 numerator;
  u32 denominator;
};
// (potential reuse in struct hclge_ptp_cycle) and so on...

  struct u32_fract fract = {
    .numerator = abs(rescale->numerator),
    .denominator = abs(rescale->denominator),
  };

// obviously we can add a macro/inliner to abs() the fract struct and
return original sign

and reuse fract.numerator, fract.denominator?

> +               *val += div_s64_rem(tmp, mult, val2);
> +
> +               /*
> +                * If only one of the rescaler elements or the schan scale is
> +                * negative, the combined scale is negative.
> +                */
> +               if (neg ^ ((rescale->numerator < 0) ^ (rescale->denominator < 0))) {
> +                       if (*val)
> +                               *val = -*val;
> +                       else
> +                               *val2 = -*val2;
> +               }


--
With Best Regards,
Andy Shevchenko

Re: [PATCH v12 09/16] iio: afe: rescale: fix accuracy for small fractional scales

[Andy Shevchenko]

On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
>
> The approximation caused by integer divisions can be costly on smaller
> scale values since the decimal part is significant compared to the
> integer part. Switch to an IIO_VAL_INT_PLUS_NANO scale type in such
> cases to maintain accuracy.

...

> +               tmp = 1 << *val2;

Unfortunately, potential UB is still here. I think you missed a subtle
detail in the implementation of BIT()/BIT_ULL(). Let's put it here:

  #define BIT(nr) (UL(1) << (nr))

where

  #define UL(x) (_UL(x))
  #define _UL(x) (_AC(x, UL))

For non-assembler case

  #define __AC(X,Y) (X##Y)
  #define _AC(X,Y) __AC(X,Y)

Now you may easily see the difference.

...

> +               rem2 = *val % (int)tmp;
> +               *val = *val / (int)tmp;
> +
> +               *val2 = rem / (int)tmp;

Hmm... You divide s64 by 10^9, which means that the maximum value can
be ~10^10 / 2 (because 2^64-1 ~= 10^19), but this _might_ be bigger
than 'int' can hold. Can you confirm that tmp can't be so big?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v12 06/16] iio: afe: rescale: expose scale processing function

[Andy Shevchenko]

On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
>
> In preparation for the addition of kunit tests, expose the logic
> responsible for combining channel scales.

...

> +/*
> + * Copyright (C) 2021 Liam Beguin <liambeguin@gmail.com>
> + */

Despite the Rb tag by the author of the code the above is wrong.
Please do not steal others work :-) (The smiley due to my believe that
you have done this undeliberately)

 * IIO rescale driver
 *
 * Copyright (C) 2018 Axentia Technologies AB
 *
 * Author: Peter Rosin <peda@axentia.se>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v12 00/16] iio: afe: add temperature rescaling support

[Andy Shevchenko]

On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
>
> Jonathan, Peter, Andy,
>
> I left out IIO_VAL_INT overflows for now, so that I can focus on getting
> the rest of these changes pulled in, but I don't mind adding a patch for
> that later on.
>
> This series focuses on adding temperature rescaling support to the IIO
> Analog Front End (AFE) driver.
>
> The first few patches address minor bugs in IIO inkernel functions, and
> prepare the AFE driver for the additional features.
>
> The main changes to the AFE driver include an initial Kunit test suite,
> support for IIO_VAL_INT_PLUS_{NANO,MICRO} scales, and support for RTDs
> and temperature transducer sensors.
>
> My apologies Andy for misunderstanding your left-shift comments, I don't
> know where my head was at... Thanks for your patience!

For the patches 1-5
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

Jonathan, perhaps you may apply them, so Liam will have less burden in
the near future.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v12 09/16] iio: afe: rescale: fix accuracy for small fractional scales

[Peter Rosin]

Hi!

On 2022-01-09 14:02, Andy Shevchenko wrote:
> On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
>>
>> The approximation caused by integer divisions can be costly on smaller
>> scale values since the decimal part is significant compared to the
>> integer part. Switch to an IIO_VAL_INT_PLUS_NANO scale type in such
>> cases to maintain accuracy.
> 

...

> ...
> 
>> +               rem2 = *val % (int)tmp;
>> +               *val = *val / (int)tmp;
>> +
>> +               *val2 = rem / (int)tmp;
> 
> Hmm... You divide s64 by 10^9, which means that the maximum value can
> be ~10^10 / 2 (because 2^64-1 ~= 10^19), but this _might_ be bigger
> than 'int' can hold. Can you confirm that tmp can't be so big?
> 

If tmp is so big that it does not fit in 32-bits, that is indeed a
problem, and it means that the scale has overflowed. However, the
problem with the scale overflowing very much existed prior to this
series. Doing something about that overflow is not strictly related
to improving the accuracy for small scale factors.

Cheers,
Peter

Re: [PATCH v12 06/16] iio: afe: rescale: expose scale processing function

[Peter Rosin]

On 2022-01-09 14:07, Andy Shevchenko wrote:
> On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
>>
>> In preparation for the addition of kunit tests, expose the logic
>> responsible for combining channel scales.
> 
> ...
> 
>> +/*
>> + * Copyright (C) 2021 Liam Beguin <liambeguin@gmail.com>
>> + */
> 
> Despite the Rb tag by the author of the code the above is wrong.
> Please do not steal others work :-) (The smiley due to my believe that
> you have done this undeliberately)
> 
>  * IIO rescale driver
>  *
>  * Copyright (C) 2018 Axentia Technologies AB
>  *
>  * Author: Peter Rosin <peda@axentia.se>
> 

For the record, I did notice this myself but did let it slide. It's only
a trivial header, and is it even copyrightable? Shrug...

Cheers,
Peter

Re: [PATCH v12 07/16] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support

[Peter Rosin]

Hi!

On 2022-01-09 13:48, Andy Shevchenko wrote:
> On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
>>
>> Some ADCs use IIO_VAL_INT_PLUS_{NANO,MICRO} scale types.
>> Add support for these to allow using the iio-rescaler with them.
> 
> ...
> 
>> +               mult = scale_type == IIO_VAL_INT_PLUS_NANO ? GIGA : MEGA;
>> +
>> +               /*
>> +                * For IIO_VAL_INT_PLUS_{MICRO,NANO} scale types if either *val
>> +                * OR *val2 is negative the schan scale is negative, i.e.
>> +                * *val = 1 and *val2 = -0.5 yields -1.5 not -0.5.
>> +                */
>> +               neg = *val < 0 || *val2 < 0;
>> +
>> +               tmp = (s64)abs(*val) * abs(rescale->numerator);
>> +               *val = div_s64_rem(tmp, abs(rescale->denominator), &rem);
>> +
>> +               tmp = (s64)rem * mult + (s64)abs(*val2) * abs(rescale->numerator);
>> +               tmp = div_s64(tmp, abs(rescale->denominator));
> 
> Isn't it too many repetitive abs() calls?
> 
> What about
> 
> // Create a macro and use for u16 (struct rn5t618_channel_ratios), s16
> (struct twl4030_prescale_divider_ratios), s32 (can be reused in struct
> rescale)
> struct u32_fract {
>   u32 numerator;
>   u32 denominator;
> };
> // (potential reuse in struct hclge_ptp_cycle) and so on...
> 
>   struct u32_fract fract = {
>     .numerator = abs(rescale->numerator),
>     .denominator = abs(rescale->denominator),
>   };
> 
> // obviously we can add a macro/inliner to abs() the fract struct and
> return original sign
> 
> and reuse fract.numerator, fract.denominator?

This feels a bit excessive when the "problem" is two extra abs calls.
I don't think the code will get any easier to read by changing
abs(rescale->denominator) into fract.denominator and with my maintainer
hat on, I vote for just letting the compiler exercise its CSE engine.

Cheers,
Peter

Re: [PATCH v12 06/16] iio: afe: rescale: expose scale processing function

[Peter Rosin]

On 2022-01-09 21:19, Peter Rosin wrote:
> On 2022-01-09 14:07, Andy Shevchenko wrote:
>> On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
>>>
>>> In preparation for the addition of kunit tests, expose the logic
>>> responsible for combining channel scales.
>>
>> ...
>>
>>> +/*
>>> + * Copyright (C) 2021 Liam Beguin <liambeguin@gmail.com>
>>> + */
>>
>> Despite the Rb tag by the author of the code the above is wrong.
>> Please do not steal others work :-) (The smiley due to my believe that
>> you have done this undeliberately)
>>
>>  * IIO rescale driver
>>  *
>>  * Copyright (C) 2018 Axentia Technologies AB
>>  *
>>  * Author: Peter Rosin <peda@axentia.se>
>>
> 
> For the record, I did notice this myself but did let it slide. It's only
> a trivial header, and is it even copyrightable? Shrug...

Oh, and by the way Liam, feel free to add a copyright line to the
iio-rescale.c file somewhere in the series if you like (if you didn't
already). You've certainly deserved it...

Cheers,
Peter

Re: [PATCH v12 07/16] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support

[Liam Beguin]

On Sun, Jan 09, 2022 at 09:20:09PM +0100, Peter Rosin wrote:
> Hi!
> 
> On 2022-01-09 13:48, Andy Shevchenko wrote:
> > On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
> >>
> >> Some ADCs use IIO_VAL_INT_PLUS_{NANO,MICRO} scale types.
> >> Add support for these to allow using the iio-rescaler with them.
> > 
> > ...
> > 
> >> +               mult = scale_type == IIO_VAL_INT_PLUS_NANO ? GIGA : MEGA;
> >> +
> >> +               /*
> >> +                * For IIO_VAL_INT_PLUS_{MICRO,NANO} scale types if either *val
> >> +                * OR *val2 is negative the schan scale is negative, i.e.
> >> +                * *val = 1 and *val2 = -0.5 yields -1.5 not -0.5.
> >> +                */
> >> +               neg = *val < 0 || *val2 < 0;
> >> +
> >> +               tmp = (s64)abs(*val) * abs(rescale->numerator);
> >> +               *val = div_s64_rem(tmp, abs(rescale->denominator), &rem);
> >> +
> >> +               tmp = (s64)rem * mult + (s64)abs(*val2) * abs(rescale->numerator);
> >> +               tmp = div_s64(tmp, abs(rescale->denominator));
> > 
> > Isn't it too many repetitive abs() calls?
> > 
> > What about
> > 
> > // Create a macro and use for u16 (struct rn5t618_channel_ratios), s16
> > (struct twl4030_prescale_divider_ratios), s32 (can be reused in struct
> > rescale)
> > struct u32_fract {
> >   u32 numerator;
> >   u32 denominator;
> > };
> > // (potential reuse in struct hclge_ptp_cycle) and so on...
> > 
> >   struct u32_fract fract = {
> >     .numerator = abs(rescale->numerator),
> >     .denominator = abs(rescale->denominator),
> >   };
> > 
> > // obviously we can add a macro/inliner to abs() the fract struct and
> > return original sign
> > 
> > and reuse fract.numerator, fract.denominator?
> 
> This feels a bit excessive when the "problem" is two extra abs calls.
> I don't think the code will get any easier to read by changing
> abs(rescale->denominator) into fract.denominator and with my maintainer
> hat on, I vote for just letting the compiler exercise its CSE engine.

I agree with Peter here, and would rather keep it as is.

Liam

> Cheers,
> Peter

Re: [PATCH v12 06/16] iio: afe: rescale: expose scale processing function

[Liam Beguin]

On Sun, Jan 09, 2022 at 03:07:58PM +0200, Andy Shevchenko wrote:
> On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
> >
> > In preparation for the addition of kunit tests, expose the logic
> > responsible for combining channel scales.
> 
> ...
> 
> > +/*
> > + * Copyright (C) 2021 Liam Beguin <liambeguin@gmail.com>
> > + */
> 
> Despite the Rb tag by the author of the code the above is wrong.
> Please do not steal others work :-) (The smiley due to my believe that
> you have done this undeliberately)

Sorry about that was not my intention.
I'll replace with Peter's original copyright.

Cheers,
Liam

>  * IIO rescale driver
>  *
>  * Copyright (C) 2018 Axentia Technologies AB
>  *
>  * Author: Peter Rosin <peda@axentia.se>
> 
> -- 
> With Best Regards,
> Andy Shevchenko

Re: [PATCH v12 06/16] iio: afe: rescale: expose scale processing function

[Liam Beguin]

On Sun, Jan 09, 2022 at 09:25:53PM +0100, Peter Rosin wrote:
> 
> 
> On 2022-01-09 21:19, Peter Rosin wrote:
> > On 2022-01-09 14:07, Andy Shevchenko wrote:
> >> On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
> >>>
> >>> In preparation for the addition of kunit tests, expose the logic
> >>> responsible for combining channel scales.
> >>
> >> ...
> >>
> >>> +/*
> >>> + * Copyright (C) 2021 Liam Beguin <liambeguin@gmail.com>
> >>> + */
> >>
> >> Despite the Rb tag by the author of the code the above is wrong.
> >> Please do not steal others work :-) (The smiley due to my believe that
> >> you have done this undeliberately)
> >>
> >>  * IIO rescale driver
> >>  *
> >>  * Copyright (C) 2018 Axentia Technologies AB
> >>  *
> >>  * Author: Peter Rosin <peda@axentia.se>
> >>
> > 
> > For the record, I did notice this myself but did let it slide. It's only
> > a trivial header, and is it even copyrightable? Shrug...
> 
> Oh, and by the way Liam, feel free to add a copyright line to the
> iio-rescale.c file somewhere in the series if you like (if you didn't
> already). You've certainly deserved it...

Thanks Peter! Sure, I'll add it somewhere in the series.

Cheers,
Liam

> Cheers,
> Peter

Re: [PATCH v12 00/16] iio: afe: add temperature rescaling support

[Jonathan Cameron]

On Sun, 9 Jan 2022 15:10:36 +0200
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
> >
> > Jonathan, Peter, Andy,
> >
> > I left out IIO_VAL_INT overflows for now, so that I can focus on getting
> > the rest of these changes pulled in, but I don't mind adding a patch for
> > that later on.
> >
> > This series focuses on adding temperature rescaling support to the IIO
> > Analog Front End (AFE) driver.
> >
> > The first few patches address minor bugs in IIO inkernel functions, and
> > prepare the AFE driver for the additional features.
> >
> > The main changes to the AFE driver include an initial Kunit test suite,
> > support for IIO_VAL_INT_PLUS_{NANO,MICRO} scales, and support for RTDs
> > and temperature transducer sensors.
> >
> > My apologies Andy for misunderstanding your left-shift comments, I don't
> > know where my head was at... Thanks for your patience!  
> 
> For the patches 1-5
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> 
> Jonathan, perhaps you may apply them, so Liam will have less burden in
> the near future.
> 
done, Patches 1-5 applied to the togreg branch of iio.git and pushed out
as testing for 0-day to see if it can find anything we missed.

I've marked the fixes for stable, but am taking these the slow way
(via next merge window) so as to keep things simple for applying the
rest of the series later this cycle.

I got a bit lost in the discussion but seems there are some minor
requests for changes so I guess I'll see a v13 of patches 6-12.

Thanks,

Jonathan

Re: [PATCH v12 00/16] iio: afe: add temperature rescaling support

[Jonathan Cameron]

On Sun, 30 Jan 2022 14:39:33 +0000
Jonathan Cameron <jic23@kernel.org> wrote:

> On Sun, 9 Jan 2022 15:10:36 +0200
> Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
> 
> > On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:  
> > >
> > > Jonathan, Peter, Andy,
> > >
> > > I left out IIO_VAL_INT overflows for now, so that I can focus on getting
> > > the rest of these changes pulled in, but I don't mind adding a patch for
> > > that later on.
> > >
> > > This series focuses on adding temperature rescaling support to the IIO
> > > Analog Front End (AFE) driver.
> > >
> > > The first few patches address minor bugs in IIO inkernel functions, and
> > > prepare the AFE driver for the additional features.
> > >
> > > The main changes to the AFE driver include an initial Kunit test suite,
> > > support for IIO_VAL_INT_PLUS_{NANO,MICRO} scales, and support for RTDs
> > > and temperature transducer sensors.
> > >
> > > My apologies Andy for misunderstanding your left-shift comments, I don't
> > > know where my head was at... Thanks for your patience!    
> > 
> > For the patches 1-5
> > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> > 
> > Jonathan, perhaps you may apply them, so Liam will have less burden in
> > the near future.
> >   
> done, Patches 1-5 applied to the togreg branch of iio.git and pushed out
> as testing for 0-day to see if it can find anything we missed.
> 
> I've marked the fixes for stable, but am taking these the slow way
> (via next merge window) so as to keep things simple for applying the
> rest of the series later this cycle.
> 
> I got a bit lost in the discussion but seems there are some minor
> requests for changes so I guess I'll see a v13 of patches 6-12.
6-16 that is!
> 
> Thanks,
> 
> Jonathan
> 
> 

Re: [PATCH v12 00/16] iio: afe: add temperature rescaling support

[Liam Beguin]

Hi Jonathan,

On Sun, Jan 30, 2022 at 02:39:33PM +0000, Jonathan Cameron wrote:
> On Sun, 9 Jan 2022 15:10:36 +0200
> Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
> 
> > On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
> > >
> > > Jonathan, Peter, Andy,
> > >
> > > I left out IIO_VAL_INT overflows for now, so that I can focus on getting
> > > the rest of these changes pulled in, but I don't mind adding a patch for
> > > that later on.
> > >
> > > This series focuses on adding temperature rescaling support to the IIO
> > > Analog Front End (AFE) driver.
> > >
> > > The first few patches address minor bugs in IIO inkernel functions, and
> > > prepare the AFE driver for the additional features.
> > >
> > > The main changes to the AFE driver include an initial Kunit test suite,
> > > support for IIO_VAL_INT_PLUS_{NANO,MICRO} scales, and support for RTDs
> > > and temperature transducer sensors.
> > >
> > > My apologies Andy for misunderstanding your left-shift comments, I don't
> > > know where my head was at... Thanks for your patience!  
> > 
> > For the patches 1-5
> > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> > 
> > Jonathan, perhaps you may apply them, so Liam will have less burden in
> > the near future.
> > 
> done, Patches 1-5 applied to the togreg branch of iio.git and pushed out
> as testing for 0-day to see if it can find anything we missed.
> 
> I've marked the fixes for stable, but am taking these the slow way
> (via next merge window) so as to keep things simple for applying the
> rest of the series later this cycle.

Thanks for taking these in.

> I got a bit lost in the discussion but seems there are some minor
> requests for changes so I guess I'll see a v13 of patches 6-12.

I'm rebasing what's left on top of your to-greg branch, and will send
out v13 today.

Cheers,
Liam

> Thanks,
> 
> Jonathan
> 
>