> -----Original Message-----
> From: Jonathan Cameron <jic23@xxxxxxxxxx>
> Sent: Sonntag, 27. November 2022 15:41
> To: linux-input@xxxxxxxxxxxxxxx; Dmitry Torokhov
> <dmitry.torokhov@xxxxxxxxx>
> Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>; Hennerich, Michael
> <Michael.Hennerich@xxxxxxxxxx>
> Subject: [PATCH 2/9] Input: ad714x - Fix padding for DMA safe buffers.
>
>
> From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
>
> On some architectures (e.g. arm64), ____cachline_aligned only aligns to the
> cacheline size of the L1 cache size. L1_CACHE_BYTES in
> arch64/include/asm/cache.h Unfortunately DMA safety on these architectures
> requires the buffer no share a last level cache cacheline given by
> ARCH_DMA_MINALIGN which has a greater granularity.
> ARCH_DMA_MINALIGN is not defined for all architectures, but when it is
> defined it is used to set the size of ARCH_KMALLOC_MINALIGN to allow DMA
> safe buffer allocations.
>
> As such the correct alignment requirement is
> __aligned(ARCH_KMALLOC_MINALIGN).
> This has recently been fixed in other subsystems such as IIO.
>
> Fixes tag is inprecise because there may not have been any architectures
> where the two values were different at the time of the earlier fix.
>
> Fixes: c0409feb8689 ("Input: ad714x - use DMA-safe buffers for spi_write()")
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> Cc: Michael Hennerich <michael.hennerich@xxxxxxxxxx>
Acked-by: Michael Hennerich <michael.hennerich@xxxxxxxxxx>
> ---
> drivers/input/misc/ad714x.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/input/misc/ad714x.h b/drivers/input/misc/ad714x.h index
> af847b5f0d0e..2b8b901183be 100644
> --- a/drivers/input/misc/ad714x.h
> +++ b/drivers/input/misc/ad714x.h
> @@ -41,7 +41,7 @@ struct ad714x_chip {
> unsigned product;
> unsigned version;
>
> - __be16 xfer_buf[16] ____cacheline_aligned;
> + __be16 xfer_buf[16] __aligned(ARCH_KMALLOC_MINALIGN);
>
> };
>
> --
> 2.38.1
