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

[Ulf Hansson]

On 29 March 2017 at 20:54, Heiner Kallweit <hkallweit1 at gmail.com> wrote:
> 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 at gmail.com>
> Tested-by: Helmut Klein <hgkr.klein at gmail.com>

Heiner, sorry for the delay!

I decided to pick this first version as it is more consistent for how
we deal with DMA friendly buffers in the core.

Thanks, applied for fixes!

Kind regards
Uffe

> ---
>  drivers/mmc/core/sdio_bus.c   | 12 +++++++++++-
>  include/linux/mmc/sdio_func.h |  2 +-
>  2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/sdio_bus.c b/drivers/mmc/core/sdio_bus.c
> index e992a7f8..2b32b889 100644
> --- a/drivers/mmc/core/sdio_bus.c
> +++ b/drivers/mmc/core/sdio_bus.c
> @@ -267,7 +267,7 @@ static void sdio_release_func(struct device *dev)
>         sdio_free_func_cis(func);
>
>         kfree(func->info);
> -
> +       kfree(func->tmpbuf);
>         kfree(func);
>  }
>
> @@ -282,6 +282,16 @@ struct sdio_func *sdio_alloc_func(struct mmc_card *card)
>         if (!func)
>                 return ERR_PTR(-ENOMEM);
>
> +       /*
> +        * allocate buffer separately to make sure it's properly aligned for
> +        * DMA usage (incl. 64 bit DMA)
> +        */
> +       func->tmpbuf = kmalloc(4, GFP_KERNEL);
> +       if (!func->tmpbuf) {
> +               kfree(func);
> +               return ERR_PTR(-ENOMEM);
> +       }
> +
>         func->card = card;
>
>         device_initialize(&func->dev);
> diff --git a/include/linux/mmc/sdio_func.h b/include/linux/mmc/sdio_func.h
> index aab032a6..97ca1053 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;        /* DMA:able scratch buffer */
>
>         unsigned                num_info;       /* number of info strings */
>         const char              **info;         /* info strings */
> --
> 2.12.1
>