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

[Oswald Buddenhagen <oswald.buddenhagen@gmx.de>]

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.

regards