Red Hat Bugzilla – Bug 97018
(SOUND AC97_CODEC)ac97_codec.c disables CMI9738 pcm volume control preventing unmute (no sound)
Last modified: 2007-04-18 12:54:41 EDT
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Description of problem:
Somewhere between kernels 2.4.20-8 and kernel-2.4.20-13.9,
drivers/sound/ac97_codec.c was patched with changes that added the CMI brand of
codecs. These codecs don't have full-on PCM volume controls and the patch
disables access to these vestigal registers. The trouble is that writing 0 to
the PCM volume control mutes them. Disabling access to these registers prevents
the subsequent initialization routines from unmuting the digital audio outputs.
Hence, no sound.
To fix this, remove the flag AC97_NO_PCM_VOLUME from the CMI entries in
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Get a sound system with a CMI ac97 codec (I've got an ECS K7S5A)
2. Install RH9 with the latest kernel & boot
3. Try to play digital audio
Actual Results: No audible digital audio
Expected Results: Should hear something
Here's the ac97_codec output from the syslog from my machine booting under
May 26 15:36:05 amadeus kernel: ac97_codec: AC97 codec, id: CMI65 (Unknown)
May 26 15:39:41 amadeus kernel: ac97_codec: AC97 codec, id: CMI65 (CMedia)
May 26 15:39:41 amadeus kernel: AC97 codec does not have proper volume support.
That fix will work (the actual problem is that we ignore the non existant volume
control but it is valid as a mute still). I've already sent Arjan a fix for this
problem with a similar codec and SIS7012
*** This bug has been marked as a duplicate of 92043 ***
Changed to 'CLOSED' state since 'RESOLVED' has been deprecated.