On 05/05/11 07:51, Alexander Stein wrote:
> req.sample needs its own cacheline otherwise accessing req.msg fetches
> it in again.
>
> Note: This effect doesn't occur if the underlying SPI driver doesn't use
> DMA at all.
I would say the comment is a bit obvious, but then you are fixing a bug
because it was wrong - so fair call.
>
> Signed-off-by: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxxxxxxxx>
Acked-by: Jonathan Cameron <jic23@xxxxxxxxx>
> ---
> This obsoletes the patch
> [PATCH 1/2] ads7846: Make buffers in ads7846_read12_ser and ads7845_read12_ser DMA save
>
> drivers/input/touchscreen/ads7846.c | 12 ++++++++++--
> 1 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
> index c24946f..ab51a8d 100644
> --- a/drivers/input/touchscreen/ads7846.c
> +++ b/drivers/input/touchscreen/ads7846.c
> @@ -281,17 +281,25 @@ struct ser_req {
> u8 command;
> u8 ref_off;
> u16 scratch;
> - __be16 sample;
> struct spi_message msg;
> struct spi_transfer xfer[6];
> + /*
> + * DMA (thus cache coherency maintenance) requires the
> + * transfer buffers to live in their own cache lines.
> + */
> + __be16 sample ____cacheline_aligned;
> };
>
> struct ads7845_ser_req {
> u8 command[3];
> u8 pwrdown[3];
> - u8 sample[3];
> struct spi_message msg;
> struct spi_transfer xfer[2];
> + /*
> + * DMA (thus cache coherency maintenance) requires the
> + * transfer buffers to live in their own cache lines.
> + */
> + u8 sample[3] ____cacheline_aligned;
> };
>
> static int ads7846_read12_ser(struct device *dev, unsigned command)
--
To unsubscribe from this list: send the line "unsubscribe linux-input" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
