[alsa-devel] trouble with alsa, wolfson, and TI OMAP35xx McBSP

Jarkko Nikula jarkko.nikula at nokia.com
Thu Apr 23 08:08:44 CEST 2009

On Wed, 22 Apr 2009 20:05:40 +0200
"ext Menon, Nishanth" <nm at ti.com> wrote:

> > Test tone is being presented by the user application, providing a
> > 1Khz tone sampled at 44.1Khz. The data are S16_LE, right channel
> > only. Left channel is quiet. The data seems to slip back and forth
> > from left to right channel. This is reproducable and verified with
> > a scope trace.
Is this slipping happening in middle of playback or between the tracks?

> I recollect this issue from years back of OSS driver -> i2s is
> configured as dual phase - mcbsp sends data on both edges, and if the
> data write happen on the wrong edge for the wrong phase, we might get
> mix up.. if I recollect right, configuration for mcbsp was done as a
> single phase with the right edge as a trigger for transfer, the
> transfer size was set as 32 bytes (both channels).. this essentially
> guarentees that mcbsp will never mix up channels.
Thanks Menon! This is sounds a information we should try out. OMAP2420
in N810 is especially suffering from channel swapping between the
tracks and I haven't found time to look any deeper :-(

I know there is a fix for DaVinci (commit
fb0ef645f2c546f8297b2fbf9b2b8fff4a7455e8) but I would like to find
out are there any other or simpler way to fix it than mixing DMA and DAI


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