Re: [PATCH 11/20] OMAP: McBSP: Add link DMA mode selection

[Jarkko Nikula <jhnikula@gmail.com>]

On Tue, 11 Aug 2009 09:18:01 +0300
Eero Nurkkala <ext-eero.nurkkala@nokia.com> wrote:

> > I would like to see this new threshold based transfer functionality to
> > be integrated so that projects can take the advantage of it and helps
> > generic PM development too but I don't want that it would cause any
> > regression now. Later on it is easy to switch threshold based transfer
> > to be the default for McBSP2 on OMAP3 but it's safer to keep current
> > mode default over one kernel release.
> > 
> 
> What regression are you addressing to? Of course in OMAP2s there could
> be issues I'm not aware of. But does this have any effect on them?
> (isn't this only OMAP3).
> 
A possible regression to a SW which is using McBSP2 on OMAP3.
There many of those boards.

The threshold based transfer will cause that omap_pcm_pointer will
loose a bit its accuracy. Probably irrelevant but still better to play
safe at least over one kernel release before making it default.

Return value prints from omap_pcm_pointer while playing
"aplay -f dat /dev/zero"

element:
614
669
691
712
734
755

threshold:
512
512
512
1024
1024
1536


-- 
Jarkko