At Sun, 13 Sep 2009 11:17:08 -0700, Bankim Bhavsar wrote: > > On Fri, Aug 28, 2009 at 12:51 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: > > At Fri, 28 Aug 2009 11:29:52 -0700, > > Bankim Bhavsar wrote: > >> > >> Takashi I came across a workaround for VMware in ALSA kernel code > >> In the comments you mention about inaccurate timer source. > >> Could you elaborate on the problem? > > > > The problem is that the irq timing emulated on vmware isn't always > > accurate. The sound hardware is supposed to issue an irq at the > > programmed buffer period. On VMware, this irq generation seems to be > > done based on the system timer (or alike), thus it's not generated > > at the accurate timing that the hardware should give. > > > > The driver has no idea whether it's on VM, thus assumed that the > > IRQ must come accurately more or less. In the recent code, there are > > some additions to correct the DMA position more to believe the accuracy > > of the IRQ than the position calculated from the hardware register. > > This caused a regression on VMware. My patch fixed that, at least, > > for VMware in the stance of previous versions. > > Thanks for the explanation, Takashi. Sorry for the delayed response. > > I tested with the fix for VMware with 2.6.31rc9 kernel. Sound playback > suffers from underruns and app terminates prematurely. > I've attached the output of "aplay sample.wav -vvv". > > I compiled kernel with following config options turned on > CONFIG_SND_DEBUG=y > CONFIG_SND_DEBUG_VERBOSE=y > CONFIG_SND_PCM_XRUN_DEBUG=y > > and set /proc/asound/card0/pcm0p/xrun_debug to 1. > > I can't seem to find ALSA xrun_debug log messages with dmesg. Am I > looking in the wrong place? > > As far as the timing of sound IRQ goes, with our emulation of ENS1371 > delay in firing interrupt ranges from 50-500 usecs. Is that large > enough to cause xruns with > recent changes? It should be fine. AFAIK, the problem was reported only by one guy, and maybe it's a kernel config issue, e.g. low HZ and/or no preempt. I can't find where the data pointer is now. Will report you back if I find from my archive. > Linux guests with kernel version 2.6.31+ running under VMware are > affected currently. > > Let me know if you need more information. > > >> Is there something specific you would like us to fix in our virtual > >> sound device or timer source? > > > > Well, the only question is how can we get the programmed sound IRQ > > more accurately... If hrtimer with the fine timer source is available, > > this could be emulated well, I guess. > > I'll consult our timer experts in VMware and get back to you on this question. That'll be great. thanks, Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
