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