On Thu, Apr 16, 2020 at 4:08 AM Alexandre Belloni
<alexandre.belloni@xxxxxxxxxxx> wrote:
>
> There is no need to keep tx_buf around, it is only used for the conversion.
>
As Lars said. And some SPI controllers may want to DMA even one byte, so, NAK.
> Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
> ---
> drivers/iio/adc/ti-ads8344.c | 18 ++++++------------
> 1 file changed, 6 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/iio/adc/ti-ads8344.c b/drivers/iio/adc/ti-ads8344.c
> index 6da50ea35217..9b2d3a8ea6bd 100644
> --- a/drivers/iio/adc/ti-ads8344.c
> +++ b/drivers/iio/adc/ti-ads8344.c
> @@ -22,13 +22,7 @@
> struct ads8344 {
> struct spi_device *spi;
> struct regulator *reg;
> - /*
> - * Lock protecting access to adc->tx_buff and rx_buff,
> - * especially from concurrent read on sysfs file.
> - */
> - struct mutex lock;
> -
> - u8 tx_buf ____cacheline_aligned;
> + struct mutex lock; /* protect from concurrent conversions */
> };
>
> #define ADS8344_VOLTAGE_CHANNEL(chan, si) \
> @@ -77,13 +71,13 @@ static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
> int ret;
> u8 buf[3];
>
> - adc->tx_buf = ADS8344_START;
> + buf[0] = ADS8344_START;
> if (!differential)
> - adc->tx_buf |= ADS8344_SINGLE_END;
> - adc->tx_buf |= ADS8344_CHANNEL(channel);
> - adc->tx_buf |= ADS8344_CLOCK_INTERNAL;
> + buf[0] |= ADS8344_SINGLE_END;
> + buf[0] |= ADS8344_CHANNEL(channel);
> + buf[0] |= ADS8344_CLOCK_INTERNAL;
>
> - ret = spi_write(spi, &adc->tx_buf, 1);
> + ret = spi_write(spi, buf, 1);
> if (ret)
> return ret;
>
> --
> 2.25.2
>
--
With Best Regards,
Andy Shevchenko
