linux-kernel - [PATCH] iio: adc: axp20x_adc: fix charging current reporting on AXP22x

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Date:   Sun,  7 Mar 2021 02:52:38 +0300
From:   Evgeny Boger <boger@...enboard.com>
To:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Evgeny Boger <boger@...enboard.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Quentin Schulz <quentin.schulz@...e-electrons.com>
Subject: [PATCH] iio: adc: axp20x_adc: fix charging current reporting on AXP22x

Both the charging and discharging currents on AXP22x are stored as
12-bit integers, in accordance with the datasheet.
It's also confirmed by vendor BSP (axp20x_adc.c:axp22_icharge_to_mA).

The scale factor of 0.5 is never mentioned in datasheet, nor in the
vendor source code. I think it was here to compensate for
erroneous additional bit in register width.

Tested on custom A40i+AXP221s board with external ammeter as
a reference.

Signed-off-by: Evgeny Boger <boger@...enboard.com>
---
 drivers/iio/adc/axp20x_adc.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/drivers/iio/adc/axp20x_adc.c b/drivers/iio/adc/axp20x_adc.c
index 3e0c0233b431..8db6699c20c3 100644
--- a/drivers/iio/adc/axp20x_adc.c
+++ b/drivers/iio/adc/axp20x_adc.c
@@ -253,17 +253,7 @@ static int axp22x_adc_raw(struct iio_dev *indio_dev,
 	struct axp20x_adc_iio *info = iio_priv(indio_dev);
 	int size;
 
-	/*
-	 * N.B.: Unlike the Chinese datasheets tell, the charging current is
-	 * stored on 12 bits, not 13 bits. Only discharging current is on 13
-	 * bits.
-	 */
-	if (chan->type == IIO_CURRENT && chan->channel == AXP22X_BATT_DISCHRG_I)
-		size = 13;
-	else
-		size = 12;
-
-	*val = axp20x_read_variable_width(info->regmap, chan->address, size);
+	*val = axp20x_read_variable_width(info->regmap, chan->address, 12);
 	if (*val < 0)
 		return *val;
 
@@ -387,7 +377,7 @@ static int axp22x_adc_scale(struct iio_chan_spec const *chan, int *val,
 
 	case IIO_CURRENT:
 		*val = 0;
-		*val2 = 500000;
+		*val2 = 1000000;
 		return IIO_VAL_INT_PLUS_MICRO;
 
 	case IIO_TEMP:
-- 
2.17.1