Re: [PATCH] ALSA: pcm: fix incorrect hw_base increase

Jaroslav Kysela
2020-05-15T09:38:06Z

Dne 15. 05. 20 v 11:04 Lu, Brent napsal(a):
>>
>> Is this a bugfix needed for older kernels as well? When did this issue show
>> up?
>>
>> thanks,
>>
>> greg k-h
>
> It happens when DMA stop moving data from host to DSP/DAI for a long time
> (> half of buffer time). I know host driver should do something about it. But if
> not, the HWSYNC will keep increasing the hw_base and hw_ptr and confuses
> user space program.

I'm afraid, but with this code, you turn off the hw_ptr jiffies code. It would
be better to fix the driver in this case (return the updated / estimated DMA
pointer, increase DMA buffer size etc.). This "lag" is unacceptable.

Jaroslav

>
> Regards,
> Brent
>

--
Jaroslav Kysela <perex@perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.