[alsa-devel] [PATCH 11/20] OMAP: McBSP: Add link DMA mode selection
eduardo.valentin at nokia.com
Fri Aug 7 15:11:02 CEST 2009
On Thu, Aug 06, 2009 at 08:15:40PM +0200, Nurkkala Eero.An (EXT-Offcode/Oulu) wrote:
> >> I would say the default mode for the omap34xx should be also element as
> >> it keeps the omap_pcm_pointer behavior the same than currently and
> >> avoids possible regression.
> > Yes, the default mode should be the element mode in my opinion as well.
> > --
> > Péter
> Well, the element mode is fine for !McBSP2. One doesn't really loose the
> buffer pointer accuracy, because you can get the last DMA irq timestamp
> with SNDRV_PCM_IOCTL_TTSTAMP (and compare that to current time).
> The accuracy is not far off from the element mode? (If you read the DMA
> portion of TRM, I think there were some issues as well)
> Don't want to be piccy, but McBSP2 with element mode is more or less like
> a "joke"? As there's a large HW bugger, why not take advantage of it..why
> "bypass" it as default?
> For !McBSP2, it doesn't even pay to have the threshold mode at all, because
> the effect on PM is actually adverse - too frequent wakeups will cause more
> adverse net effect on PM (IIRC) @ VBAT.
I agree with Eero in this point. We can set mcbsp2 default op mode to threshold.
I think we are even here :) two believe that must be element mode by default,
while two want default threshold (at least for mcbsp2). We need another opinion.
> - Eero --
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