2015-07-07 20:05 GMT+09:00 Alban Browaeys <alban.browaeys@xxxxxxxxx>:
> Removed the residual rest to zero on last descriptor.
>
> Also set residue granularity to BURST instead of SEGMENT.
> This last item needs more investigation before I could give a rationale
> for it.
>
> Signed-off-by: Alban Browaeys <prahal@xxxxxxxxx>
> Reported-by: gabriel@xxxxxxxxx
> Reported-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
> Fixes: aee4d1fac887 ("dmaengine: pl330: improve pl330_tx_status()
> function")
>
Hi,
I am not quite sure what bug you are trying to fix here. It isn't
described in commit message. Also I don't get why the residue=0 is
being removed. This will break the residue calculation...
Some time ago I posted a patch fixing sound issues on Odroid XU3.
Today Vinod applied it:
https://git.kernel.org/cgit/linux/kernel/git/vkoul/slave-dma.git/commit/?h=fixes&id=5dd90e5b91e0f5c925b12b132c7cd27538870256
I don't know if this is the same issue... can you describe exactly
what you are trying to fix, why and how?
Best regards,
Krzysztof
> ---
>
> My older local version of the residue :
> https://github.com/prahal/linux/blob/odroid-3.19/drivers/dma/pl330.c#L2230
>
> I took a second look at both and noticed that in the upstream version,
> I was not able to make sense of the "if desc->last then reset residual
> to zero" in the loop. Early tests gives a proper sound ouput with it
> removed.
>
> More tests are welcome, and it could be the flag change is wrong.
>
> There is also a bad interaction with pulseaudio when the buffer size is
> small : https://bugs.freedesktop.org/show_bug.cgi?id=84878. This
> might affect testing.
> ---
> drivers/dma/pl330.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index f513f77..0851f41 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -2275,8 +2275,6 @@ pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
> }
> break;
> }
> - if (desc->last)
> - residual = 0;
> }
> spin_unlock_irqrestore(&pch->lock, flags);
>
> @@ -2890,7 +2888,7 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id)
> pd->src_addr_widths = PL330_DMA_BUSWIDTHS;
> pd->dst_addr_widths = PL330_DMA_BUSWIDTHS;
> pd->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
> - pd->residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
> + pd->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
>
> ret = dma_async_device_register(pd);
> if (ret) {
> --
> 2.1.4
>
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