Am 29.03.2017 um 22:56 schrieb Heiner Kallweit:
> Certain 64-bit systems (e.g. Amlogic Meson GX) require buffers to be
> used for DMA to be 8-byte-aligned. struct sdio_func has an embedded
> small DMA buffer not meeting this requirement.
> Testing an extension to meson-gx driver for switching to descriptor
> chain mode broke SDIO therefore. Aligning tmpbuf to a 8-byte
> boundary fixed the driver behavior.
>
> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> Tested-by: Helmut Klein <hgkr.klein@xxxxxxxxx>
> ---
> v2:
> - switch to much simpler version as suggested by Kevin Hilman <khilman@xxxxxxxxxxxx>
> - adjust commit message
> ---
> include/linux/mmc/sdio_func.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/mmc/sdio_func.h b/include/linux/mmc/sdio_func.h
> index aab032a6..65d90f76 100644
> --- a/include/linux/mmc/sdio_func.h
> +++ b/include/linux/mmc/sdio_func.h
> @@ -53,7 +53,8 @@ struct sdio_func {
> unsigned int state; /* function state */
> #define SDIO_STATE_PRESENT (1<<0) /* present in sysfs */
>
> - u8 tmpbuf[4]; /* DMA:able scratch buffer */
> + /* take care of proper alignment for DMA on certain 64-bit systems */
> + u8 __aligned(8) tmpbuf[4]; /* DMA:able scratch buffer */
>
> unsigned num_info; /* number of info strings */
> const char **info; /* info strings */
>
Ulf, do you have an opinion on this one? A related patch was just applied to
the brcmfmac WiFi driver -> https://patchwork.kernel.org/patch/9665425/
In sum WiFi over SDIO would be ok an systems requiring 8 byte aligned
DMA buffers (at least systems using the brcmfmac driver).
OK here means that no fallback to bounce buffer mode is necessary.
Rgds, Heiner
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