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Message-Id: <20220208020441.3081162-4-liambeguin@gmail.com>
Date: Mon, 7 Feb 2022 21:04:33 -0500
From: Liam Beguin <liambeguin@...il.com>
To: liambeguin@...il.com, peda@...ntia.se, jic23@...nel.org,
andy.shevchenko@...il.com, lars@...afoo.de
Cc: linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
devicetree@...r.kernel.org, robh+dt@...nel.org
Subject: [PATCH v14 03/11] iio: afe: rescale: add offset support
This is a preparatory change required for the addition of temperature
sensing front ends.
Signed-off-by: Liam Beguin <liambeguin@...il.com>
Reviewed-by: Peter Rosin <peda@...ntia.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@...il.com>
*
* Author: Peter Rosin <peda@...ntia.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__ */
--
2.35.1.4.g5d01301f2b86
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