[U-Boot] [PATCH V2 4/4] mmc: tegra: use bounce buffer APIs

[Simon Glass]

Hi Stephen,

On Tue, Nov 6, 2012 at 1:27 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
> From: Stephen Warren <swarren at nvidia.com>
>
> Tegra's MMC driver does DMA, and hence needs cache-aligned buffers. In
> some cases (e.g. user load commands) this cannot be guaranteed by callers
> of the MMC APIs. To solve this, modify the Tegra MMC driver to use the
> new bounce_buffer_*() APIs.
>
> Note: Ideally, all U-Boot code will always provide address- and size-
> aligned buffers, so a bounce buffer will only ever be needed for user-
> supplied buffers (e.g. load commands). Ensuring this removes the need
> for performance-sucking bounce buffer cache management and memcpy()s.
> The one known exception at present is the SCR buffer in sd_change_freq(),
> which is only 8 bytes long. Solving this requires enhancing struct
> mmc_data to know the difference between buffer size and transferred data
> size, or forcing all callers of mmc_send_cmd() to have allocated buffers
> using ALLOC_CACHE_ALIGN_BUFFER(), which while true in this case, is not
> enforced in any way at present, and so cannot be assumed by the core MMC
> code.
>
> Signed-off-by: Stephen Warren <swarren at nvidia.com>

Tested on Seaboard, loading a kernel from ext2 partition.

Acked-by: Simon Glass <sjg at chromium.org>
Tested-by: Simon Glass <sjg at chromium.org>

It's really nice to clean up the cache code as well, very slick.

Regards,
Simon