[alsa-devel] HD-audio runtime->delay accounting
david.henningsson at canonical.com
Fri Sep 21 14:16:43 CEST 2012
On 09/21/2012 01:59 PM, Takashi Iwai wrote:
> recently Pierre questioned about the validity of COMBO positioning
> mode, and it turned out that the position reporting can be handled
> better if we take the difference between LPIB and DMAPOS as
> runtime->delay. (In short, LPIB points the position where the data fed
> to the codec, and DMAPOS points the data fetched to DMA.)
> We cooked up a test patch below and it seems working well on a few
> machines I've tested. I think we might have still chance to put this
> into 3.7, as this would be a good improvement. The patch below is a
> combined work of two fixes: fixing the better stream start by always
> using SSYNC bit, and adjusting the position and runtime->delay.
Interesting. A quick question: is this affecting playback, recording, or
> Of course, the biggest question is the test coverage.
> David, could you check whether this doesn't break so much on (some)
> machines you can test? Of course, if any other people can test it,
> it'll be a great help, too.
> The patch should be applied to the latest sound.git tree master
> branch, but it should be applicable (and easily resolvable) for older
Against sound master:
patching file sound/pci/hda/hda_intel.c
Hunk #2 succeeded at 1987 (offset -17 lines).
Hunk #3 succeeded at 2012 (offset -17 lines).
Hunk #4 succeeded at 2044 (offset -17 lines).
Hunk #5 succeeded at 2144 (offset -17 lines).
Hunk #6 succeeded at 3426 (offset -104 lines).
Hunk #7 succeeded at 3490 (offset -104 lines).
> The patch extends this new mode only for recent Intel
> chips, just to be sure.
I don't think I have much such hardware here. But I've made DKMS package
for easy testing by others. If you're running Ubuntu 12.04, you can just
install this package, reboot, and test:
David Henningsson, Canonical Ltd.
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