linux-kernel - [PATCH 1/3] iio: adc: ti-ads8344: properly byte swap value

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Date:   Wed, 15 Apr 2020 23:22:55 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Gregory CLEMENT <gregory.clement@...tlin.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: [PATCH 1/3] iio: adc: ti-ads8344: properly byte swap value

The first received byte is the MSB, followed by the LSB so the value needs
to be byte swapped.

Also, the ADC actually has a delay of one clock on the SPI bus. Read three
bytes to get the last bit.

Fixes: 8dd2d7c0fed7 ("iio: adc: Add driver for the TI ADS8344 A/DC chips")
Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
---
 drivers/iio/adc/ti-ads8344.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/adc/ti-ads8344.c b/drivers/iio/adc/ti-ads8344.c
index 9a460807d46d..6da50ea35217 100644
--- a/drivers/iio/adc/ti-ads8344.c
+++ b/drivers/iio/adc/ti-ads8344.c
@@ -29,7 +29,6 @@ struct ads8344 {
 	struct mutex lock;
 
 	u8 tx_buf ____cacheline_aligned;
-	u16 rx_buf;
 };
 
 #define ADS8344_VOLTAGE_CHANNEL(chan, si)				\
@@ -76,6 +75,7 @@ static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
 {
 	struct spi_device *spi = adc->spi;
 	int ret;
+	u8 buf[3];
 
 	adc->tx_buf = ADS8344_START;
 	if (!differential)
@@ -89,11 +89,11 @@ static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
 
 	udelay(9);
 
-	ret = spi_read(spi, &adc->rx_buf, 2);
+	ret = spi_read(spi, buf, sizeof(buf));
 	if (ret)
 		return ret;
 
-	return adc->rx_buf;
+	return buf[0] << 9 | buf[1] << 1 | buf[2] >> 7;
 }
 
 static int ads8344_read_raw(struct iio_dev *iio,
-- 
2.25.2