[alsa-devel] [PATCH v2 6/6] pcm: Update pcm->avail_min with needed_slave_avail_min, after reading unaligned frames

[Takashi Iwai]

On Tue, 16 Jul 2019 05:58:15 +0200,
Channaiah Vanitha (RBEI/ECF3) wrote:
> 
> Hello Jaroslav-san, Takashi-san,
> 
> Can you please reply your feedback for below mail chain.
> 
> Best regards,
> Vanitha Channaiah 
> RBEI/ECF3
> 
> _____________________________________________
> From: Channaiah Vanitha (RBEI/ECF3) 
> Sent: Tuesday, June 18, 2019 4:45 AM
> To: 'Jaroslav Kysela' <perex at perex.cz>; Takashi Iwai <tiwai at suse.de>
> Cc: Wischer Timo (ADITG/ESS) <twischer at de.adit-jv.com>; alsa-devel at alsa-project.org
> Subject: RE: [alsa-devel] [PATCH v2 6/6] pcm: Update pcm->avail_min with needed_slave_avail_min, after reading unaligned frames
> 
> 
> Hello Jaroslav-san, Takashi-san,
> 
> > Which hardware exactly? The hw_ptr should be reset when the streaming starts.
> > It appears that the problem is specific to the direct plugins only when the period wakeups are a bit different than for the direct hardware access.
> 
> Firstly, sorry for late reply.
> 
> Issue is seen in RCar Kingfischer H3 es2.0 target.	
> 
> The issue was seen during the below commit :
> commit 07b7acb51d283d8469696c906b91f1882696a4d4
> ("ASoC: rsnd: update pointer more accurate")
> https://patchwork.kernel.org/patch/9772671/
> 
> 
> There could be a non-uniform jitter exists between when interrupt raised [rcar_dmac_isr_channel(), rcar_dmac_isr_channel_thread()]
> and the interrupt is processed to read/calculate the DMA position [dma_set_residue()]
> This could result in unaligned hw_ptr reported at user-space alsa lib.

It looks rather like a workaround for the bug in driver.
Better fix the driver instead.


thanks,

Takashi