|author||Takashi Iwai <email@example.com>||2010-04-01 18:08:29 +0200|
|committer||Takashi Iwai <firstname.lastname@example.org>||2010-04-01 18:08:29 +0200|
ALSA: hda - Update document about MSI and interrupts
Signed-off-by: Takashi Iwai <email@example.com>
Diffstat (limited to 'Documentation/sound')
1 files changed, 12 insertions, 4 deletions
diff --git a/Documentation/sound/alsa/HD-Audio.txt b/Documentation/sound/alsa/HD-Audio.txt
index f4dd3bf99d1..98d14cb8a85 100644
@@ -119,10 +119,18 @@ the codec slots 0 and 1 no matter what the hardware reports.
-In rare but some cases, the interrupt isn't properly handled as
-default. You would notice this by the DMA transfer error reported by
-ALSA PCM core, for example. Using MSI might help in such a case.
-Pass `enable_msi=1` option for enabling MSI.
+HD-audio driver uses MSI as default (if available) since 2.6.33
+kernel as MSI works better on some machines, and in general, it's
+better for performance. However, Nvidia controllers showed bad
+regressions with MSI (especially in a combination with AMD chipset),
+thus we disabled MSI for them.
+There seem also still other devices that don't work with MSI. If you
+see a regression wrt the sound quality (stuttering, etc) or a lock-up
+in the recent kernel, try to pass `enable_msi=0` option to disable
+MSI. If it works, you can add the known bad device to the blacklist
+defined in hda_intel.c. In such a case, please report and give the
+patch back to the upstream developer.