[PATCH] ARM: tegra: cpuidle: use CPUIDLE_FLAG_TIMER_STOP flag

[Joseph Lo]

On Fri, 2013-07-19 at 18:52 +0800, Daniel Lezcano wrote:
> On 07/19/2013 09:14 AM, Joseph Lo wrote:
> > On Thu, 2013-07-18 at 20:41 +0800, Daniel Lezcano wrote:
> >> On 07/18/2013 01:08 PM, Joseph Lo wrote:
> >>> On Thu, 2013-07-18 at 04:31 +0800, Stephen Warren wrote:
> >>>> On 07/17/2013 04:15 AM, Joseph Lo wrote:
> >>>>> On Wed, 2013-07-17 at 03:51 +0800, Stephen Warren wrote:
> >>>>>> On 07/16/2013 05:17 AM, Joseph Lo wrote:
> >>>>>>> On Tue, 2013-07-16 at 02:04 +0800, Stephen Warren wrote:
> >>>>>>>> On 06/25/2013 03:23 AM, Joseph Lo wrote:
> >>>>>>>>> Use the CPUIDLE_FLAG_TIMER_STOP and let the cpuidle framework
> >>>>>>>>> to handle the CLOCK_EVT_NOTIFY_BROADCAST_ENTER/EXIT when entering
> >>>>>>>>> this state.
> >>>> ... [ discussion of issues with Joesph's patches applied]
> >>>>>
> >>>>> OK. I did more stress tests last night and today. I found it cause by
> >>>>> the patch "ARM: tegra: cpuidle: use CPUIDLE_FLAG_TIMER_STOP flag" and
> >>>>> only impact the Tegra20 platform. The hot plug regression seems due to
> >>>>> this patch. After dropping this patch on top of v3.11-rc1, the Tegra20
> >>>>> can back to normal.
> >>>>>
> >>>>> And the hop plug and suspend stress test can pass on Tegra30/114 too.
> >>>>>
> >>>>> Can the other two patch series for Tegra114 to support CPU idle power
> >>>>> down mode and system suspend still moving forward, not be blocked by
> >>>>> this patch?
> >>>>>
> >>>>> Looks the CPUIDLE_FLAG_TIMER_STOP flag still cause some other issue for
> >>>>> hot plug on Tegra20, I will continue to check this. You can just drop
> >>>>> this patch.
> >>>>
> >>>> OK, if I drop that patch, then everything on Tegra20 and Tegra30 seems
> >>>> fine again.
> >>>>
> >>>> However, I've found some new and exciting issue on Tegra114!
> >>>>
> >>>> With unmodified v3.11-rc1, I can do the following without issue:
> >>>>
> >>>> * Unplug/replug CPUs, so that I had all combinations of CPU 1, 2, 3
> >>>> plugged/unpplugged (with CPU 0 always plugged).
> >>>>
> >>>> * Unplug/replug CPUs, so that I had all combinations of CPU 0, 1, 2, 3
> >>>> plugged/unpplugged (with the obvious exception of never having all CPUs
> >>>> unplugged).
> >>>>
> >>>> However, if I try this with your Tegra114 cpuidle and suspend patches
> >>>> applied, I see the following issues:
> >>>>
> >>>> 1) If I boot, unplug CPU 0, then replug CPU 0, the system immediately
> >>>> hard-hangs.
> >>>>
> >>> Sorry, I didn't apply the hotplug stress test on CPU0 too much. Because
> >>> all of our use cases and stress tests are focused on secondary CPUs
> >>> only.
> >>>
> >>> After doing some tests, here is my summary. This issue happens after we
> >>> support CPU idle power-down mode and relates to PMC or flow controller I
> >>> believe.
> >>>
> >>> i) on top of v3.11-rc1 (only support WFI in CPU idle)
> >>> When hot unplug CPU0, the PMC can power gate and put it into reset
> >>> state. This is what I expect and also true on all the other secondary
> >>> CPUs. The flow controller can maintain the CPU power state machine as
> >>> what we want.
> >>>
> >>> ii) on top of v3.11-rc1 + CPU idle power down mode support
> >>> a) I saw most of the time the CPU0,1,2,3 were in power down and reset
> >>> status. That means the idle power down mode works fine.
> >>>
> >>> b) Testing with the CPU hotplug stress test with the secondary CPUs (not
> >>> include CPU0), the result is good too.
> >>>
> >>> c) Testing hot plug on CPU0 with CPUIDLE_FLAG_TIMER_STOP apply or not
> >>> apply (Note 1), the result shows not good to me. The CPU0 have already
> >>> gone into WFI and the flow controller is set as WAITFOREVENT mode. But
> >>> the PMC always can't power gate CPU0 and sometimes can put it into
> >>> reset, but sometimes can't. That's why you can see it hanging after
> >>> unplug CPU0 sometimes.
> >>
> >> Are sure coupled idle state support hotplug and especially the cpu0
> >> hotplug ?
> > 
> > Tegra114 didn't use coupled idle framework.
> 
> Ok, so the problem occurs with the CPUIDLE_FLAG_TIMER_STOP flag only on
> tegra114, right ?
> 
> Sorry, I am a bit lost :)
> 
Here are the issues that happen after apply CPUIDLE_FLAG_TIMER_STOP.
1) Tegra114/30
The warning message at kernel/time/tick-broadcast.c:667
tick_broadcast_oneshot_control could be triggered when doing CPU hot
plug stress test.

2) Tegra20
The system is easy to stick or become lag.
The CPU hot plug is easy to cause system stick too.

The fix I suggested in another mail looks can fix all the issues above.
I verified it again today on 3 different Tegra SoC platforms.

Thanks,
Joseph