Re: [PATCH] [RFC PATCH] dmaengine: pl330: residual - do not reset on last descriptor.

[Alban Browaeys <alban.browaeys@gmail.com>]

Le mardi 07 juillet 2015 à 20:53 +0900, Krzysztof Kozlowski a écrit :
> 2015-07-07 20:05 GMT+09:00 Alban Browaeys <alban.browaeys@gmail.com>:
> > 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@yahoo.com>
> > Reported-by: gabriel@unseen.is
> > Reported-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> > 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?
> 
> 

This was about "choppy sound" issue left after the dma pause fix:
https://www.mail-archive.com/linux-samsung
-soc%40vger.kernel.org/msg44567.html

From a glance at the commit you mention I would say it is the same
issue. Will try this commit instead in a few hours and report.


Thanks
Alban


> choppy sound) on Odroid XU3-Lite. On current linux-next
> (next-20150612) the sound is awful (choppy) after few seconds of 
> play.
> For example first four of:
> $ aplay /usr/share/sounds/alsa/Front_Right.wav
> work fine. But then it just gets worse and underruns are reported:
> $ Playing WAVE '/usr/share/sounds/alsa/Front_Right.wav' : Signed 16
> bit Little Endian, Rate 48000 Hz, Mono
> $ underrun!!! (at least 0.095 ms long)