[PATCH 3/3] ARM: tegra114: cpuidle: add powered-down state

[Joseph Lo]

On Fri, 2013-05-31 at 17:27 +0800, Daniel Lezcano wrote:
> On 05/31/2013 11:12 AM, Joseph Lo wrote:
> > Hi Daniel,
> > 
> > Thanks for your review.
> > 
> > On Thu, 2013-05-30 at 22:35 +0800, Daniel Lezcano wrote:
> >> On 05/30/2013 01:19 PM, Joseph Lo wrote:
> >>> This supports CPU core power down on each CPU when CPU idle. When CPU go
> >>> into this state, it saves it's context and needs a proper configuration
> >>> in flow controller to power gate the CPU when CPU runs into WFI
> >>> instruction. And the CPU also needs to set the IRQ as CPU power down idle
> >>> wake up event in flow controller.
> >>>
> >>> Signed-off-by: Joseph Lo <josephl at nvidia.com>
> >>> ---
> >>
> >> Hi Joseph,
> >>
> >> a new flag has been added in the cpuidle framework to let this one to
> >> handle the timer broadcast : CPUIDLE_FLAG_TIMER_STOP
> >>
> >> It is the commit b60e6a0eb0273132cbb60a9806abf5f47a4aee1c
> >>
> >> You can get rid of the clockevent notify stuff by adding this flag to
> >> the state.
> >>
> > 
> > I just tested this flag on Tegra20, 30 and 114. It is only OK on
> > Tegra20. It caused a warning message below on Tegra30/114 at boot time.
> > 
> > I gave it a quick check I found it can't clean
> > tick_broadcast_pending_mask sometimes if apply the flag. But I keep the
> > code right now it's always OK. Not sure why? 
> 
> Is it possible you didn't intialized the timer broadcast with
> CLOCK_EVT_NOTIFY_BROADCAST_ON in the driver and then this one is
> actually disabled for you driver ?
> 
I found if I don't apply the CPUIDLE_FLAG_TIMER_STOP flag, the function
"cpuidle_setup_broadcast_timer" (drivers/cpuidle/driver.c) would not be
called. Then it's OK.

If I apply this flag (with no CONFIG_CPU_IDLE_MULTIPLE_DRIVERS), the
cpuidle_register_driver only register for CPU0. Then the
"cpuidle_setup_broadcast_timer" only turn on for CPU0. I think this
might be the root cause. Not sure this also can reproduce on the other
SoCs?