Re: [PATCH] mmc: sdio: fix alignment issue in struct sdio_func

Kevin Hilman
2017-03-29T20:17:35Z

Heiner Kallweit <hkallweit1@gmail.com> writes:

> 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.
> When testing switching to descriptor chain mode in meson-gx driver
> SDIO is broken therefore. Fix this by allocating the small DMA buffer
> separately as kmalloc ensures that the returned memory area is
> properly aligned for every basic data type.
>
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> Tested-by: Helmut Klein <hgkr.klein@gmail.com>

This should work too, without the need to do a tiny kmalloc.

diff --git a/include/linux/mmc/sdio_func.h b/include/linux/mmc/sdio_func.h
index aab032a6ae61..071addf23931 100644
--- a/include/linux/mmc/sdio_func.h
+++ b/include/linux/mmc/sdio_func.h
@@ -53,7 +53,7 @@ struct sdio_func {
unsigned int state; /* function state */
#define SDIO_STATE_PRESENT (1<<0) /* present in sysfs */

- u8 tmpbuf[4]; /* DMA:able scratch buffer */
+ u8 tmpbuf[4] __aligned(8); /* DMA:able scratch buffer */

unsigned num_info; /* number of info strings */
const char **info; /* info strings */

Kevin