[PATCH] ARM: perf: add PMU hotplug notifiery

[lorenzo.pieralisi@arm.com (Lorenzo Pieralisi)]

On Thu, Feb 23, 2012 at 04:12:59PM +0000, Ashwin Chaugule wrote:
> On 2/23/2012 11:04 AM, Will Deacon wrote:
> > 
> > Ok. Note that the perf core will actually destroy perf events on a hotplug
> > down notification, so profiling runs will be dead on that core even if it
> > comes back up.
> > 
> > This patch just ensures that we have a sane state in the control registers
> > given that their state is UNKNOWN out of reset. Adding full hotplug support
> > to perf (that is, supporting hotplug events during a run and representing
> > that in a meaningful way) is a larger issue.
> > 
> >>> I'll send a link to my code once the git server is up. It's a bit flaky today.
> > 
> > Ok, cool. Are you happy with me to proceed with the current code for the
> > time being?
> > 
> 
> Sure. We'll need to be able to distinguish between a hotplug and a CPU
> power-collapse / deep sleep / what-have-you state in this code at some
> point since they all have a different effect on the PMU regs.

I have a patch to save/restore PMU regs from idle, I will send it to
Will for review soon so that he can merge the bits that you both deem
worthwhile.

save/restore will be called from CPU PM notifiers on deep-sleep
entry/exit, it is up to the idle state enter function to trigger them when PMU
state is lost.

Thanks,
Lorenzo