iio: afe: iio-rescale: Support processed channels

It happens that an ADC will only provide raw or processed
voltage conversion channels. (adc/ab8500-gpadc.c).
On the Samsung GT-I9070 this is used for a light sensor
and current sense amplifier so we need to think of something.

The idea is to allow processed channels and scale them
with 1/1 and then the rescaler can modify the result
on top.

Link: https://lore.kernel.org/linux-iio/20201101232211.1194304-1-linus.walleij@linaro.org/
Cc: Peter Rosin <peda@axentia.se>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Peter Rosin <peda@axentia.se>
Link: https://lore.kernel.org/r/20210518092741.403080-1-linus.walleij@linaro.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index e42ea2b..774eb30 100644 (file)
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -29,6 +29,7 @@ struct rescale {
        struct iio_channel *source;
        struct iio_chan_spec chan;
        struct iio_chan_spec_ext_info *ext_info;
+       bool chan_processed;
        s32 numerator;
        s32 denominator;
 };
@@ -43,10 +44,27 @@ static int rescale_read_raw(struct iio_dev *indio_dev,
 
        switch (mask) {
        case IIO_CHAN_INFO_RAW:
-               return iio_read_channel_raw(rescale->source, val);
+               if (rescale->chan_processed)
+                       /*
+                        * When only processed channels are supported, we
+                        * read the processed data and scale it by 1/1
+                        * augmented with whatever the rescaler has calculated.
+                        */
+                       return iio_read_channel_processed(rescale->source, val);
+               else
+                       return iio_read_channel_raw(rescale->source, val);
 
        case IIO_CHAN_INFO_SCALE:
-               ret = iio_read_channel_scale(rescale->source, val, val2);
+               if (rescale->chan_processed) {
+                       /*
+                        * Processed channels are scaled 1-to-1
+                        */
+                       *val = 1;
+                       *val2 = 1;
+                       ret = IIO_VAL_FRACTIONAL;
+               } else {
+                       ret = iio_read_channel_scale(rescale->source, val, val2);
+               }
                switch (ret) {
                case IIO_VAL_FRACTIONAL:
                        *val *= rescale->numerator;
@@ -130,16 +148,27 @@ static int rescale_configure_channel(struct device *dev,
        chan->ext_info = rescale->ext_info;
        chan->type = rescale->cfg->type;
 
-       if (!iio_channel_has_info(schan, IIO_CHAN_INFO_RAW) ||
-           !iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE)) {
-               dev_err(dev, "source channel does not support raw/scale\n");
+       if (iio_channel_has_info(schan, IIO_CHAN_INFO_RAW) ||
+           iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE)) {
+               dev_info(dev, "using raw+scale source channel\n");
+       } else if (iio_channel_has_info(schan, IIO_CHAN_INFO_PROCESSED)) {
+               dev_info(dev, "using processed channel\n");
+               rescale->chan_processed = true;
+       } else {
+               dev_err(dev, "source channel is not supported\n");
                return -EINVAL;
        }
 
        chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
                BIT(IIO_CHAN_INFO_SCALE);
 
-       if (iio_channel_has_available(schan, IIO_CHAN_INFO_RAW))
+       /*
+        * Using .read_avail() is fringe to begin with and makes no sense
+        * whatsoever for processed channels, so we make sure that this cannot
+        * be called on a processed channel.
+        */
+       if (iio_channel_has_available(schan, IIO_CHAN_INFO_RAW) &&
+           !rescale->chan_processed)
                chan->info_mask_separate_available |= BIT(IIO_CHAN_INFO_RAW);
 
        return 0;