On 05-06-18, 18:59, Janusz Krzysztofik wrote:
> Commit 0198d7bb8a0c ("ASoC: omap-mcbsp: Convert to use the sdma-pcm
> instead of omap-pcm") resulted in broken audio playback on OMAP1510
> (discovered on Amstrad Delta).
>
> When running on OMAP1510, omap-pcm used to obtain DMA offset from
> snd_dmaengine_pcm_pointer_no_residue() based on DMA interrupt triggered
> software calculations instead of snd_dmaengine_pcm_pointer() which
> depended on residue value calculated from omap_dma_get_src_pos().
> Similar code path is still available in now used
> sound/soc/soc-generic-dmaengine-pcm.c but it is not triggered.
>
> It was verified already before that omap_get_dma_src_pos() from
> arch/arm/plat-omap/dma.c didn't work correctly for OMAP1510 - see
> commit 1bdd7419910c ("ASoC: OMAP: fix OMAP1510 broken PCM pointer
> callback") for details. Apparently the same applies to its successor,
> omap_dma_get_src_pos() from drivers/dma/ti/omap-dma.c.
>
> On the other hand, snd_dmaengine_pcm_pointer_no_residue() is described
> as depreciated and discouraged for use in new drivers because of its
> unreliable accuracy. However, it seems the only working option for
> OPAM1510 now, as long as a software calculated residue is not
> implemented as OMAP1510 fallback in omap-dma.
>
> Using snd_dmaengine_pcm_pointer_no_residue() code path instead of
> snd_dmaengine_pcm_pointer() in sound/soc/soc-generic-dmaengine-pcm.c
> can be triggered in two ways:
> - by passing pcm->flags |= SND_DMAENGINE_PCM_FLAG_NO_RESIDUE from
> sound/soc/omap/sdma-pcm.c,
> - by passing dma_caps.residue_granularity =
> DMA_RESIDUE_GRANULARITY_DESCRIPTOR from DMA engine.
>
> Let's do the latter.
>
> Created and tested against next-20180531 tag from linux-next tree.
This is not useful for log.
I have stripped this and applied
--
~Vinod
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