Re: [PATCH v2] dmaengine: imx-sdma: Correct src_addr_widths and directions

From: Nicolin Chen
Date: Thu Sep 14 2017 - 17:48:42 EST

On Thu, Sep 14, 2017 at 04:43:08PM -0300, Fabio Estevam wrote:
> Hi Nicolin,
> On Thu, Sep 14, 2017 at 3:46 PM, Nicolin Chen <nicoleotsuka@xxxxxxxxx> wrote:
> > The driver already supports DMA_DEV_TO_DEV in sdma_config(),
> > sdma_prep_slave_sg(). So this patch adds them to the lists.
> >
> > Signed-off-by: Nicolin Chen <nicoleotsuka@xxxxxxxxx>
> Patch looks good.
> Just curious: what is the specific usecase that triggered this change?

Any audio test case. The ASoC generic dmaengine gets the DMA
cap (4_BYTES only) and apply it to hw->formats in ASoC core.
SSI + WM8962 could have S8_LE, S16_LE and S24_LE formats but
it turns out that it only has S24_LE now because of this.

I haven't seen any side effect by DMA_DEV_TO_DEV yet but it
could potentially break ASRC once a similar constrain based
on the "directions" is applied.