FAILED: patch "[PATCH] iio: mtk-auxadc: fix case IIO_CHAN_INFO_PROCESSED" failed to apply to 4.9-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.9-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;
 
 	default: