iio: mtk-auxadc: fix case IIO_CHAN_INFO_PROCESSED

commit c2980c64c7fd4585d684574c92d1624d44961edd upstream.

The previous driver does't apply the necessary scaling to take the
voltage range into account.
We change readback value from raw data to input voltage to fix case
IIO_CHAN_INFO_PROCESSED.

Fixes: ace4cdfe67be ("iio: adc: mt2701: Add Mediatek auxadc driver for mt2701.")
Signed-off-by: Hui Liu <hui.liu@mediatek.com>
Link: https://lore.kernel.org/r/20210926073028.11045-2-hui.liu@mediatek.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iio/adc/mt6577_auxadc.c b/drivers/iio/adc/mt6577_auxadc.c
index 79c1dd6..d4fccd5 100644 (file)
--- a/drivers/iio/adc/mt6577_auxadc.c
+++ b/drivers/iio/adc/mt6577_auxadc.c
@@ -82,6 +82,10 @@ static const struct iio_chan_spec mt6577_auxadc_iio_channels[] = {
        MT6577_AUXADC_CHANNEL(15),
 };
 
+/* For Voltage calculation */
+#define VOLTAGE_FULL_RANGE  1500       /* VA voltage */
+#define AUXADC_PRECISE      4096       /* 12 bits */
+
 static int mt_auxadc_get_cali_data(int rawdata, bool enable_cali)
 {
        return rawdata;
@@ -191,6 +195,10 @@ static int mt6577_auxadc_read_raw(struct iio_dev *indio_dev,
                }
                if (adc_dev->dev_comp->sample_data_cali)
                        *val = mt_auxadc_get_cali_data(*val, true);
+
+               /* Convert adc raw data to voltage: 0 - 1500 mV */
+               *val = *val * VOLTAGE_FULL_RANGE / AUXADC_PRECISE;
+
                return IIO_VAL_INT;
 
        default: