On Tue, May 1, 2012 at 6:25 AM, Kevin Hilman [off-list ref] wrote:

Unfortunately, digging in the code isn't going to help much.

We've been trying to get our heads around some undocumented reset
behavior for the various debug IPs in OMAP.

After a little digging and clarification from HW designers, it appears
that if we allow the EMU clockdomain to idle, a full reset of the debug
IPs is done. ?That means there are two solutions to this problem:

1) don't ever alow EMU clockdomain to idle.
2) modify CTI driver to re-init for every use.

Obviously (1) is the easiet, and hacks for that have already been
posted, but that has pretty significant impacts on power savings. ?(2)
is the right solution to merge upstream, but needs writing.

For (2), using runtime PM methods in the driver would be the simplest
here since the ->runtime_resume method will be called every time the
device is about to be used.

The previous patch has supported runtime pm on omap4 pmu[1], but still
didn't fix the problem. Could you comment on the patch and point out
the proper way to support pmu runtime for fixing the problem?


[1], http://marc.info/?l=linux-arm-kernel&m=131946777028358&w=2

Thanks,
--
Ming Lei