[alsa-devel] [PATCH 1/2] OMAP3: MCBSP: Suspend/resume failure fix

[Aggarwal, Anuj]

> > Looking at the very original patch, I don't know how things could get
> > into deep sleep by disabling the fclk only... need to disable the iclk
> > also. In threshold mode, HW autogates the iclk, so you may be just
> > "lucky".
> [Anuj] No, I am not :(. I had to modify the original patch to include
> the disable part for the ICLK too. Without that, I was not able to hit
> retention.
> I will try to do some further regression on OMAP3 EVM and post my
> findings. As of now, audio is working fine with these patches + ICLK
> modification.
[Aggarwal, Anuj] After further testing, I found that there is some
problem in the capture path. While capturing in background, if I tried 
to do suspend, capture fails after a few seconds giving;
arecord: pcm_read:1617: read error: Input/output error
This I was discussing in another thread (*) for AIC23/AM3517 on NFS but now
I realized after finishing my tests that this behavior is common for 
both omap3530/twl4030 and am3517/aic23. Moreover, the problem doesn't 
depend on the underlying file system - both NFS and ramdisk produce the
same error. 
To make matter worse, if suspend/resume is tried while audio
loopback is running, system just hangs. Even telnet to the evm doesn't work.
So the audio capture path, from suspend/resume point of view, definitely
needs some more time.
I will continue debugging at my end. But pointers are always welcome.

*) http://www.mail-archive.com/linux-omap@vger.kernel.org/msg19845.html
> >
> > One may want to be aware of this also:
> >
> > http://git.kernel.org/?p=linux/kernel/git/tmlind/linux-omap-
> 2.6.git;a=commitdiff;h=72cc6d715d5b018e2cff4adb68966855850d4e77
> >
> > I think it's an undocumented feature.
> >