[alsa-devel] channel swapping issue on OMAP3/TWL4030 is back

Daniel Mack zonque at gmail.com
Fri Mar 22 10:07:34 CET 2013

On 22.03.2013 10:03, Peter Meerwald wrote:
>>> I'm running Linux 3.7 on a beagle-xm and observe very reproducible stereo 
>>> channel swapping issue on playback of a stereo stream (one channel has a 
>>> sine, the other is zero); the channel swap occurs on starting the playback
>> Always? Or in like 50% of the runs? And is the record stream (IOW: the
>> clocks) already running when you switch on playback?
> in 10 runs, the swap can maybe observed 3 times; so: not always
> I can easily turn on/off the clock for the McBSP3/TLV320AIC3104 setup; 
> with McBSP3 being master I ONLY have the issue when the clock is already 
> running; when I start the stream first, then turn on the clock, there is 

Yes, that sounds familiar. I guess the problem is that the serial line
driver does not respect a specific slope (like lo->hi) but will sync up
to *any* slope once it gets its enable bit set. Which will give you
arbitrary channel swaps.


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