[alsa-devel] [RFC PATCH v2 08/12] ASoC: Samsung: Do not queue cyclic buffers multiple times

[Linus Walleij]

On Sat, Jun 22, 2013 at 10:42 PM, Tomasz Figa <tomasz.figa at gmail.com> wrote:

> The legacy S3C-DMA API required every period of a cyclic buffer to be
> queued separately. After conversion of Samsung ASoC to Samsung DMA
> wrappers somebody made an assumption that the same is needed for DMA
> engine API, which is not true.
>
> In effect, Samsung ASoC DMA code was queuing the whole cyclic buffer
> multiple times with a shift of one period per iteration, leading to:
>   a) severe memory waste - up to 13x times more DMA transfer descriptors
>      are allocated than needed,
>   b) possible memory corruption, because further cyclic buffers were out
>      of the original buffers, due to the offset.
>
> This patch fixes this problem by making the legacy S3C-DMA API use the
> same semantics as DMA engine (the whole cyclic buffer is enqueued at
> once) and modifying users of Samsung DMA wrappers in cyclic mode to
> behave appropriately.
>
> Signed-off-by: Tomasz Figa <tomasz.figa at gmail.com>

Acked-by: Linus Walleij <linus.walleij at linaro.org>

Yours,
Linus Walleij