[alsa-devel] Suspend/Resume failure of Alsa but OSS emulation still works
My embedded system's audio is not resuming after the system resumes from suspend to RAM, below is a detailed discription of the problem and what I have done, to date, to identify the source of the problem.
I have tested the following scenario with several audio applications such as Alsa aplay and ogg123: If I have an audio player (aplay or ogg123) using Alsa and I suspend my system to RAM when the system wakes up (resumes) there is no sound. If I kill the audio player and start it back up the sound returns so it seems the act of opening and closing Alsa fixes the failure. During the "no sound state" I also opened alsamixer and adjusted (successfully) several alsa settings including volume but the sound still did not resume until I restarted the player.
I also configured one player to use the OSS (emulated by Alsa). When I used the emulated OSS audio driver (/dev/dsp) the sound did resume after the system woke up (resumed) from memory so everything WORKED! I then configured the player back to use the native Alsa driver and again there was no sound after resume.
Has anyone seen this issue before or does anyone have additional tests or debugging ideas they can recommend to further narrow down the issue. I'm very comfortable with modifying and compiling the Kernel so please do not limit your suggestions to user-space tweaks.
Embedded System Information: Processor: ARM/Xscale (PXA270) Audio Codec: AC97 (UCB1400) alsa lib version: 1.0.24.1 Linux Kernel Version: 2.6.39.2
Regards, Shane
All, I also saved the alsa registers before and after suspend/resume: "cat /proc/asound/card0/codec97#0/ac97#0-0+regs > file" and did a diff on the 2 files, there was no difference. Regards, Shane
On Wed, Jul 13, 2011 at 3:01 PM, Shane Volpe shanevolpe@gmail.com wrote:
My embedded system's audio is not resuming after the system resumes from suspend to RAM, below is a detailed discription of the problem and what I have done, to date, to identify the source of the problem.
I have tested the following scenario with several audio applications such as Alsa aplay and ogg123: If I have an audio player (aplay or ogg123) using Alsa and I suspend my system to RAM when the system wakes up (resumes) there is no sound. If I kill the audio player and start it back up the sound returns so it seems the act of opening and closing Alsa fixes the failure. During the "no sound state" I also opened alsamixer and adjusted (successfully) several alsa settings including volume but the sound still did not resume until I restarted the player.
I also configured one player to use the OSS (emulated by Alsa). When I used the emulated OSS audio driver (/dev/dsp) the sound did resume after the system woke up (resumed) from memory so everything WORKED! I then configured the player back to use the native Alsa driver and again there was no sound after resume.
Has anyone seen this issue before or does anyone have additional tests or debugging ideas they can recommend to further narrow down the issue. I'm very comfortable with modifying and compiling the Kernel so please do not limit your suggestions to user-space tweaks.
Embedded System Information: Processor: ARM/Xscale (PXA270) Audio Codec: AC97 (UCB1400) alsa lib version: 1.0.24.1 Linux Kernel Version: 2.6.39.2
Regards, Shane
If I kill the audio player and start it back up the sound returns so it seems the act of opening and closing Alsa fixes the failure. During the "no sound state" I also opened alsamixer and adjusted (successfully) several alsa settings including volume but the sound still did not resume until I restarted the player.
If I do an strace on aplayer and look at its output after the resume it looks like aplayer is hanging up on trying to read /dev/snd/timer and is getting -1 EAGAIN (Resource temporarily unavailable) from it. I would greatly appreciate any comments or suggestions of what I can do next to further narrow down the problem Regards, Shane
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Shane Volpe