[alsa-devel] [PATCH 11/20] OMAP: McBSP: Add link DMA mode selection

ext-Eero.Nurkkala at nokia.com ext-Eero.Nurkkala at nokia.com
Thu Aug 6 20:15:40 CEST 2009

>> 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.

- Eero --
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