From f890987fac8153227258121740a9609668c427f3 Mon Sep 17 00:00:00 2001
From: Wilfried Wessner <wilfried.wessner@gmail.com>
Date: Mon, 8 Feb 2021 15:27:05 +0100
Subject: [PATCH] iio: adc: ad7949: fix wrong ADC result due to incorrect bit mask
Git-commit: f890987fac8153227258121740a9609668c427f3
Patch-mainline: v5.12-rc4
References: git-fixes

Fixes a wrong bit mask used for the ADC's result, which was caused by an
improper usage of the GENMASK() macro. The bits higher than ADC's
resolution are undefined and if not masked out correctly, a wrong result
can be given. The GENMASK() macro indexing is zero based, so the mask has
to go from [resolution - 1 , 0].

Fixes: 7f40e0614317f ("iio:adc:ad7949: Add AD7949 ADC driver family")
Signed-off-by: Wilfried Wessner <wilfried.wessner@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Charles-Antoine Couret <charles-antoine.couret@essensium.com>
Cc: <Stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210208142705.GA51260@ubuntu
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/iio/adc/ad7949.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
index 5d597e5050f6..1b4b3203e428 100644
--- a/drivers/iio/adc/ad7949.c
+++ b/drivers/iio/adc/ad7949.c
@@ -91,7 +91,7 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
 	int ret;
 	int i;
 	int bits_per_word = ad7949_adc->resolution;
-	int mask = GENMASK(ad7949_adc->resolution, 0);
+	int mask = GENMASK(ad7949_adc->resolution - 1, 0);
 	struct spi_message msg;
 	struct spi_transfer tx[] = {
 		{
-- 
2.26.2