oprofile and ARM A9 hardware counter

[Ming Lei]

On Tue, May 1, 2012 at 6:25 AM, Kevin Hilman <khilman at ti.com> 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