On Wed, 2006-05-24 at 08:15 +1000, Benjamin Herrenschmidt wrote:

quoted

Right, that's how snd-powermac does it. It has the nasty side-effect of
polluting the cache a lot though, since dbdma commands are 16 bytes
long. Am I wrong?

You don't have that much DBDMA commands that it would pollute the cache
_a lot_ :) 

Ah, yeah, I guess so. Well I do have 32 dbdma commands, them being
spaced up in 16-bytes means 16 cachelines, no? I'm not sure how the
cache is wired up ...

quoted

Alsa calls this thing the 'pointer' :) The frame counter we currently
use is the frame counter register of the i2s bus controller, and I don't
see why we shouldn't do that instead of reading back all the dbdma
command status fields.

If you manage to have it properly in sync, that may work too.

Seems to work fine so far, even if bcm43xx kills a few interrupts ;)

johannes