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[2/3] iio: adc: ti-ads8344: remove tx_buf from driver data

Message ID 20200415212257.161238-3-alexandre.belloni@bootlin.com
State New, archived
Headers show
Series iio: adc: ti-ads8344: improve the driver | expand

Commit Message

Alexandre Belloni April 15, 2020, 9:22 p.m. UTC
There is no need to keep tx_buf around, it is only used for the conversion.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
 drivers/iio/adc/ti-ads8344.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

Comments

Lars-Peter Clausen April 16, 2020, 6:26 a.m. UTC | #1
On 4/15/20 11:22 PM, Alexandre Belloni wrote:
> There is no need to keep tx_buf around, it is only used for the conversion.
>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> ---
>   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];

spi_write() might use the buffer in a DMA transfer, so it can't be on 
the stack and needs to be in its own cacheline.

>   
> -	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;
>
Andy Shevchenko April 17, 2020, 10:24 a.m. UTC | #2
On Thu, Apr 16, 2020 at 4:08 AM Alexandre Belloni
<alexandre.belloni@bootlin.com> 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@bootlin.com>
> ---
>  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
>
diff mbox series

Patch

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;