[Bug 28106] radeon KMS causes hardware conflict/interference with Intel wifi and audio, crashes wireless

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=28106

--- Comment #15 from Øyvind Stegard <oyvinst at ifi.uio.no> 2010-05-18 13:05:53 PDT ---
The test setup I use to quickly reproduce and verify that the problem is there:

1) Play a pure sound which easily revelase playback glitches:
$ gst-launch-0.10 audiotestsrc ! pulsesink

2) Play some video (doesn't matter what) with MPlayer, using plain x11 output
and no sound:
$ mplayer /path/to/some/movie.avi -vo x11 -zoom -nosound

3) Test audio starts glitching and the glitching becomes worse if I put the
video in fullscreen.

And some observations about test:

1) There is not much load on system during test (MPlayer uses around 40% CPU,
Xorg floats under 12% CPU, for a 1024x576 video with no sound).

2) There is a lot less audio glitching if I run things in a completely
composited environment (e.g. Compiz with no unredirection for fullscreen
windows). If I *do* unredirect fullscreen windows with Compiz the glitching
becomes worse in fullscreen.

3) There is alomst no glitching at all if using XV for video playback in the
test, instead of plain old x11. Obviously that's not going to help for apps
that don't use XV, like fullscreen Flash video streaming or any affected
non-video app.

4) The glitching is worse when video window is full screen.

5) HDA intel driver typically always reports that IRQ timing work-around has
been activated. This doesn't happen in UMS-mode.


And some observations not just related to the specific test setup:
1) Flash fullscreen video playback causes more severe audio glitches if *not*
running composited in fullscreen, for instance under Compiz with "Unredirect
fullscreen windows" enabled. This is what typically also takes down wireless
(just happened now with current setup, as I was testing Flash and writing
this).

2) Flash fullscreen video causes glitches even when redirected in composited
env.

3) Flash doesn't use XV, seems to correspond well with MPlayer -vo x11 being
much worse than when using -vo xv.

4) There are no playback issues with video during any of these tests, the video
is smooth, system not overloaded. And besides, the test sound generator
requires almost no resources at all.

5) [ 1535.437114] CE: hpet increased min_delta_ns to 7500 nsec
Don't really know the meaning of this one, but it typically appears during
problems with wireless and/or audio when running under KMS. Kernel compensating
for what is seen as accuracy issues with system timing ?

6) It doesn't have to be MPlayer-vo-x11 or Flash that triggers problem, I just
use them because they so easily reproduce it. I have heard audio popping when
scrolling Firefox pages or moving windows around, and I've managed to take down
wireless when launching Neverball (OpenGL-game). 

7) No matter what IRQ config or snd-hda-intel options I test, the problems are
always there with KMS and disappear with UMS.

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