[alsa-devel] [PATCHv4 0/2] McBSP: OMAP3: Add sidetone feature

Peter Ujfalusi peter.ujfalusi at nokia.com
Fri Feb 19 09:34:32 CET 2010

On Thursday 18 February 2010 22:22:29 ext Jarkko Nikula wrote:
> I still have two concern:
> 1. port number vs. index difference inside driver code is not enough
> It's just confusing if a machine driver and internal API (mcbsp.c) has
> to use different indexing. See:
> omap_mcbsp_st_add_controls(codec, 2);
> ...
> *(unsigned int *)omap3beagle_dai.cpu_dai->private_data = 1; /* McBSP2 */


> and mcbsp->id use in mcbsp.c.

It has always bothered me, I'll take a look and check if there is a reason why 
it is like that, and if possible I'll change the mcbsp->id to be 0 based (thus 
harmonizing the internal and external interface).
> 2. I cannot change the sidetone level with alsamixer
> Is this bug with the alsamixer? With amixer I'm able to set positive
> values but not negative
> amixer set -D hw:0 'McBSP2 Sidetone Channel 0' 32767
> What I'm looking here, is that I can execute a test below with unit
> impulse response tap filter, hear the sound and note that the volume is
> changing as I'm changing the sidetone volume :-)

I'm not sure, but you might need to configure the taps as well to have the 
correct sidetone.
Also I have a recollection, that the McBSP sidetone requires DSP mode (TDM) in 
order to operate correctly, so on Beagle you might need to set up 4 channel 
mode. And how the channel mapping in 4 channel mode works in McBSP sidetone is 
another matter...

> arecord -f dat >/dev/null |aplay -f dat /dev/zero


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