Re: [PATCH] ALSA: pcm: fix wait_time calculations

[Jon Hunter <jonathanh@nvidia.com>]

On 12/06/2023 15:28, Oswald Buddenhagen wrote:
> On Mon, Jun 12, 2023 at 02:16:15PM +0100, Jon Hunter wrote:
>> On 12/06/2023 13:18, Jon Hunter wrote:
>>> On 05/04/2023 21:12, Oswald Buddenhagen wrote:
>>>> ... in wait_for_avail() and snd_pcm_drain().
>>>
>>> Sorry for not catching this sooner, but I have just noticed that one 
>>> of our audio tests for Tegra is failing on v6.4-rc and bisect is 
>>> pointing to this commit. Reverting this on top of the current 
>>> mainline fixes it.
>>>
>> If I enable the debug prints, I do see the following messages ...
>>
>>  tegra-audio-graph-card sound: capture read timeout (DMA or IRQ trouble?)
>>
> yes, this is the kind of fallout one would expect from this change, as 
> it significantly shortened the effective timeout under most circumstances.
> 
> first check that there isn't a genuine underlying bug, that is, that the 
> unusually slow timings match expectations.
> 
> if everything looks right, then properly codify the timeout in the 
> driver by setting substream->wait_time as required.
> the lazy approach of more or less restoring the previous status quo 
> would be setting it to 10000 in the `open` callback.
> fwiw, soc/sof sets it to 500, which may actually be a bad idea (it's 
> short enough that a very long period time would exceed it, if such is 
> permitted). and it's not obvious why it does that.


Yes I can see now that reducing the timeout is causing the problem here. 
I can try a few settings to see what works.

Thanks
Jon

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