Commit a29c3283 authored by Liam Beguin's avatar Liam Beguin Committed by Jonathan Cameron
Browse files

iio: afe: rescale: add offset support 



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

Signed-off-by: default avatarLiam Beguin <liambeguin@gmail.com>
Reviewed-by: default avatarPeter Rosin <peda@axentia.se>
Reviewed-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220213025739.2561834-4-liambeguin@gmail.com


Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent 701ee14d

drivers/iio/afe/iio-rescale.c

+81 −0
Original line number Diff line number Diff line
@@ -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>

 */
@@ -81,11 +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 * 1000000000LL;

		tmp2 = ((s64)scale * 1000000000LL) + scale2;

		*val = div64_s64(tmp, tmp2) + schan_off;

		return IIO_VAL_INT;

	case IIO_VAL_INT_PLUS_MICRO:

		tmp = (s64)rescale->offset * 1000000LL;

		tmp2 = ((s64)scale * 1000000LL) + 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) {
@@ -112,6 +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;

	}
@@ -188,6 +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
@@ -352,6 +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)

include/linux/iio/afe/rescale.h

+4 −0
Original line number Diff line number Diff line
@@ -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__ */