diff mbox series

[v14,03/11] iio: afe: rescale: add offset support

Message ID 20220208020441.3081162-4-liambeguin@gmail.com (mailing list archive)
State Superseded
Headers show
Series iio: afe: add temperature rescaling support | expand

Commit Message

Liam Beguin Feb. 8, 2022, 2:04 a.m. UTC 
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   | 81 +++++++++++++++++++++++++++++++++
 include/linux/iio/afe/rescale.h |  4 ++
 2 files changed, 85 insertions(+)

Comments

Andy Shevchenko Feb. 8, 2022, 1:42 p.m. UTC | #1 
On Tue, Feb 8, 2022 at 4:04 AM Liam Beguin <liambeguin@gmail.com> wrote:
>
> This is a preparatory change required for the addition of temperature
> sensing front ends.

...

> +               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;

Wonder if this actually should be

   if (ret < 0)
       return ret;
   if (ret != ...)
       return -EOP...;

> +               }
Liam Beguin Feb. 9, 2022, 4:35 p.m. UTC | #2 
Hi Andy,

On Tue, Feb 08, 2022 at 03:42:22PM +0200, Andy Shevchenko wrote:
> On Tue, Feb 8, 2022 at 4:04 AM Liam Beguin <liambeguin@gmail.com> wrote:
> >
> > This is a preparatory change required for the addition of temperature
> > sensing front ends.
> 
> ...
> 
> > +               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;
> 
> Wonder if this actually should be
> 
>    if (ret < 0)
>        return ret;
>    if (ret != ...)
>        return -EOP...;

Unless someone has a stong objection, I'd rather keep it as is.

Cheers,
Liam

> > +               }
> 
> -- 
> With Best Regards,
> Andy Shevchenko
Peter Rosin Feb. 10, 2022, 4:47 p.m. UTC | #3 
Hi!

On 2022-02-08 03:04, Liam Beguin wrote:
> 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   | 81 +++++++++++++++++++++++++++++++++
>  include/linux/iio/afe/rescale.h |  4 ++
>  2 files changed, 85 insertions(+)
> 
> diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
> index f833eb38f8bb..63035b4bce5e 100644
> --- a/drivers/iio/afe/iio-rescale.c
> +++ b/drivers/iio/afe/iio-rescale.c
> @@ -3,6 +3,7 @@
>   * IIO rescale driver
>   *
>   * Copyright (C) 2018 Axentia Technologies AB
> + * Copyright (C) 2022 Liam Beguin <liambeguin@gmail.com>
>   *
>   * Author: Peter Rosin <peda@axentia.se>
>   */
> @@ -82,11 +83,46 @@ 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;

Same thing here as in patch 2/11, use NANO or the raw number. GIGA
has no connection to the usage.

> +		*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;

And MICRO here of course.

Cheers,
Peter

*snip*
diff mbox series

Patch

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index f833eb38f8bb..63035b4bce5e 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -3,6 +3,7 @@ 
  * IIO rescale driver
  *
  * Copyright (C) 2018 Axentia Technologies AB
+ * Copyright (C) 2022 Liam Beguin <liambeguin@gmail.com>
  *
  * Author: Peter Rosin <peda@axentia.se>
  */
@@ -82,11 +83,46 @@  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 +149,47 @@  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 +266,9 @@  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 +433,7 @@  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 8a2eb34af327..6eecb435488f 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__ */