Messages in this thread | | | Subject | Re: [PATCH 1/3] iio: adc: ti-ads8344: properly byte swap value | From | Lars-Peter Clausen <> | Date | Thu, 16 Apr 2020 08:29:45 +0200 |
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On 4/15/20 11:22 PM, Alexandre Belloni wrote: > 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@bootlin.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]; Same as with spi_write(), spi_read() transfer buffers should not be on the stack in case the driver tries to use it for DMA. > > 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,
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