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dmaengine: ti: omap-dma: Fix OMAP1510 incorrect residue_granularity 

Commit 0198d7bb8a ("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 1bdd741991 ("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.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Janusz Krzysztofik 2018-06-05 18:59:57 +02:00 committed by Vinod Koul
parent ce397d215c
commit c9bd0946da
1 changed files with 5 additions and 1 deletions
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4
drivers/dma/ti/omap-dma.c
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@ -1485,6 +1485,10 @@ static int omap_dma_probe(struct platform_device *pdev)
od->ddev.src_addr_widths = OMAP_DMA_BUSWIDTHS;
od->ddev.dst_addr_widths = OMAP_DMA_BUSWIDTHS;
od->ddev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
if (__dma_omap15xx(od->plat->dma_attr))
od->ddev.residue_granularity =
DMA_RESIDUE_GRANULARITY_DESCRIPTOR;
else
od->ddev.residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
od->ddev.max_burst = SZ_16M - 1; /* CCEN: 24bit unsigned */
od->ddev.dev = &pdev->dev;