The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From c2980c64c7fd4585d684574c92d1624d44961edd Mon Sep 17 00:00:00 2001
From: Hui Liu hui.liu@mediatek.com Date: Sun, 26 Sep 2021 15:30:28 +0800 Subject: [PATCH] iio: mtk-auxadc: fix case IIO_CHAN_INFO_PROCESSED
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
diff --git a/drivers/iio/adc/mt6577_auxadc.c b/drivers/iio/adc/mt6577_auxadc.c index 79c1dd68b909..d4fccd52ef08 100644 --- 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;
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