Re: [RFC 2/4] ARM: OMAP: PM: Get rid of Powerdomain book-keeping from cpuidle

[Tero Kristo <t-kristo@ti.com>]

On Fri, 2012-07-20 at 13:38 +0530, Rajendra Nayak wrote:
> On Friday 20 July 2012 12:55 PM, Shilimkar, Santosh wrote:
> > On Fri, Jul 20, 2012 at 11:34 AM, Rajendra Nayak<rnayak@ti.com>  wrote:
> >> pwrdm_pre_transition()/pwrdm_post_transition() have always been high latency
> >> operations done within cpuidle to do Powerdomain level book-keeping to know
> >> what state transitions for different Powerdomains have been triggered.
> >> This is also useful to do a restore-on-demand in some cases when we know
> >> the context for the given Powerdomain was lost etc.
> >>
> >> Now that we have definitive entry/exit points (thanks to the Powerdomain
> >> level usecounting) for Powerdomain transitions, these book-keeping functions
> >> can very well be moved from within CPUidle into pwrdm_clkdm_enable()/pwrdm_
> >> clkdm_disable() functions.
> >>
> >> Also rename _pwrdm_pre/post_transition_cb() to pwrdm_pre/post_transition()
> >> and get rid of the original ones which iterate over all powerdomains.
> >>
> >> Signed-off-by: Rajendra Nayak<rnayak@ti.com>
> >> ---
> >>   arch/arm/mach-omap2/omap-mpuss-lowpower.c |    4 ++--
> >>   arch/arm/mach-omap2/pm34xx.c              |    4 ++--
> >>   arch/arm/mach-omap2/powerdomain.c         |   28 ++++++++--------------------
> >>   arch/arm/mach-omap2/powerdomain.h         |    4 ++--
> >>   4 files changed, 14 insertions(+), 26 deletions(-)
> >>
> >> diff --git a/arch/arm/mach-omap2/omap-mpuss-lowpower.c b/arch/arm/mach-omap2/omap-mpuss-lowpower.c
> >> index 13670aa..ea19439 100644
> >> --- a/arch/arm/mach-omap2/omap-mpuss-lowpower.c
> >> +++ b/arch/arm/mach-omap2/omap-mpuss-lowpower.c
> >> @@ -255,7 +255,7 @@ int omap4_enter_lowpower(unsigned int cpu, unsigned int power_state)
> >>                  return -ENXIO;
> >>          }
> >>
> >> -       pwrdm_pre_transition();
> >> +       pwrdm_cpu_idle();
> >>
> > Glad to see this is getting optimized.
> > I haven't seen how "pwrdm_cpu_[idle/wakeup]()" is
> > implemented but will those work on SMP system ?
> > I mean OMAP4, any CPU can make this call ?
> 
> Thats a good question. I think Tero did this so he can kick in
> voltage transitions at the right time in idle/suspend.
> Given that these deal with incrementing/decrementing the MPU and CORE
> pwrdm usecounts alone, maybe on OMAP4 (SMP systems) this needs to also
> increment/decrement the specific CPU usecounts on the CPUs these calls
> are made.

Yeah, you should keep the usecounts valid by each cpu separately calling
these functions. My current set only sets these usecounts based on cpu0
activity, as cpu1 is statically controlled through cpu online / offline.
Once per-cpu cpuidle is in, these should be changed so that each
individual cpu increases the usecounts when they are brought up,
decrease/increase during idle, and decrease when they are brought down.
The usecount should always reflect the number of CPUs active on MPU
domain.

-Tero