[alsa-devel] AT32AP7000 (AVR32) + WM8510

Geoffrey Wossum geoffrey at pager.net
Sat May 24 00:56:00 CEST 2008

On Thursday 22 May 2008 06:11:31 pm Geoffrey Wossum wrote:
> On Thursday 22 May 2008 05:48:41 pm Mark Brown wrote:
> > On Thu, May 22, 2008 at 02:57:41PM -0500, Geoffrey Wossum wrote:
> > > Looks like it should work to me.  Note that I do hear a pop from the
> > > speaker the first time I try to play a file.  Here's a dump of the
> > > registers while I'm trying to play a file with aplay.  I'm combing
> > > through them right now to see if I can find anything that looks off.
> >
> > I'll have a look at it at some point, but not right now :) .  I should
> > also have asked you if you could post your machine driver - if you'd
> > rather post it off-list that'd be fine.

Ok, I got it working.  It can now play "I'm sorry, Dave.  I'm afraid I can't 
do that."  This should be the audio equivalent of "Hello world" :)

First, I changed it so the AVR32 provided the BCLK and FRAME.  I could never 
get the WM8510 to generate what looked like proper FRAMES.  I did continue 
using the WM8510's PLL to generate the DAC clock.  With the AVR32 providing 
the clocks, I at least got some noise out of it.

After a lot of head scratching and analyzing register settings and what not, I 
realized that I had based my AVR32 platform drivers on the AT91.  The AT91 is 
little endian, the AVR32 is big endian.  Changing all the SNDRV_PCM_FMTBIT_ 
settings to be BE instead of LE changed the noise into the files I was trying 
to play.

Finally, I really had to lie in the wm8510 code and say that it supported a 
minimum of 2 channels, and a maximum of 2 channels.  This makes sense from 
the data sheet, since it still wants a left and a right channel of data, and 
just throws one away.

A few questions:

I had to change the WM8510's format to say that it wanted big endian.  Should 
the CODEC (and platform and machine) be setup just to say that it uses 
SNDRV_PCM_FMTBIT_S16 instead of SNDRV_PCM_FMTBIT_S16_LE/BE?  Looks from 
sound/pcm.h this should just do the Right Thing.

Any idea why I couldn't get the WM8510 to generate the FRAME signal properly?  
Like I said before, it generated a 44.1 kHz frame no matter the BCLK divider 
or the word length were set to.

Thanks for the help!  As soon as I get the code cleaned up some, I'll 
contribute the AVR32 platform driver code.


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