[alsa-devel] WM8731 using I2S on omap3 McBSP2 issues
jhnikula at gmail.com
Mon Sep 28 07:50:32 CEST 2009
On Sat, 26 Sep 2009 08:59:52 -0700
Rick Bronson <rick at efn.org> wrote:
> Yes, I had tried 8 before and just tried it now. Same result. It
> really seems like there is a DMA issue. Can you think of anything
> else to try before I dive into the DMA code?
Ok, that wasn't the reason.
Have you tried to reverse roles of codec and omap? I.e. by using
the codec as a master and omap as a slave with SND_SOC_DAIFMT_CBM_CFM.
I don't think there is any HW reason as you have seen the bit-clock and
frame sync signals toggling but I remember one case few years back
where codec had slight too high capacitive load on the bit-clock line.
That was then causing unstable frame sync as it was internally derived
directly from the bit-clock pin without any buffer. Bit-clock signal
looked just fine on oscilloscope but wasn't well enough for internal
circuits of the cpu.
So if assuming similar problem here, I could imagine that if the FSX is
used similar way directly inside the omap and if signal is not well
enough, the McBSP and DMA may not be running.
This migh be a bit far reason to look for but at least easy to try by
switching the roles as then the codec is driving the both bit-clock and
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