[alsa-devel] Channel swapping problem on Atmel SSC audio

Irfan Shaikh irfan.shaikh at sasken.com
Fri Nov 12 10:52:00 CET 2010

I had faced the similar issue on IMx31. The cause there was reversal of LRCK clock {180 degree phase shift}.
probing the LRCK clock may help you to find the problem

From: alsa-devel-bounces at alsa-project.org [alsa-devel-bounces at alsa-project.org] On Behalf Of Patrick Ziegler [patrick.ziegler at fh-kl.de]
Sent: Friday, November 12, 2010 1:36 PM
To: alsa-devel at alsa-project.org
Cc: Ryan Mallon
Subject: Re: [alsa-devel] Channel swapping problem on Atmel SSC audio

Am 11.11.2010 13:27, schrieb Alan Horstmann:
> On Wednesday 10 November 2010 22:49, Ryan Mallon wrote:
>> I'm working on a custom board using the AT91SAM9G45 processor and a
>> TLV320AIC26 SPI attached audio codec using I2S format audio. When doing
>> audio playback on the board the left and right channels are occasionally
>> flipped.
> <snip>
>> Has anybody else had this problem, or does anybody have any AT91/Atmel
>> hardware that they could test to see if it occurs on other hardware also?
> I have worked with the AT91SAM9260 on a project which is currently suspended
> (other priorities), where we had a simiar problem, with a codec on SPI.
> Every time audio was started (capture or playback) the channels could be
> swapped.  Solving that issue remains TODO when we restart.
> There was a thread on alsa-devel last month 'Soc Atmel SSC stereo problem'
> with some suggestions.
In the thread mentioned, Alan proposed me amongst other things to test
the LRCK level before starting the SSC. This works well for me. Maybe it
should be implemented in a more generic way but the following
modification does the trick for me.

in function  atmel_pcm_trigger inside file sound/soc/atmel/atmel-pcm.c :





Dipl.-Inf. (FH) Patrick Ziegler

University Of Applied Sciences

Amerikastrasse 1
D-66482 Zweibruecken

Phone:  +49 631 3724 5526
Mail:   patrick.ziegler at fh-kl.de


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