Re: [PATCH V3 0/3] ARM: tegra114: cpuidle: add power down state

[Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>]

On 06/25/2013 03:23 AM, Joseph Lo wrote:
> This series introduce CPU core power down state for 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.
> 
> To prevent race conditions and ensure proper interrupt routing on
> Cortex-A15 CPUs when they are power-gated, add a CPU PM notifier
> call-back to reprogram the GIC CPU interface on PM entry. The
> GIC CPU interface will be reset back to its normal state by
> the common GIC CPU PM exit callback when the CPU wakes up.
> 
> This series depends on the patch of "tick:  Fix
> tick_broadcast_pending_mask not cleared".

Joseph, I applied all 3 of your patches/series on top of next-20130701,
which does include dependency "tick:  Fix tick_broadcast_pending_mask
not cleared":

* ARM: tegra: cpuidle: use CPUIDLE_FLAG_TIMER_STOP flag
* This series
* ARM: tegra114: add support for system suspend

I find that at least on on Tegra114/Dalmore, CPU hotplug doesn't work
correctly.

If I unplug CPU0, I get an immediate system hang:

root@localhost:~# ./cpuonline.py
echo 0 > /sys/devices/system/cpu/cpu0/online
[   73.555696] IRQ73 no longer affine to CPU0
[   73.561965] CPU0: shutdown

If I adjust my script not to hotplug CPU0, I get a hang when plugging a
CPU back in:

root@localhost:~# ./cpuonline.py
echo 0 > /sys/devices/system/cpu/cpu2/online
[   87.141128] CPU2: shutdown
echo 0 > /sys/devices/system/cpu/cpu1/online
[   89.227597] CPU1: shutdown
echo 0 > /sys/devices/system/cpu/cpu3/online
[   91.253870] CPU3: shutdown
echo 1 > /sys/devices/system/cpu/cpu1/online

or simpler:

root@localhost:~# echo 0 > /sys/devices/system/cpu/cpu1/online
[   80.767825] CPU1: shutdown
root@localhost:~# echo 1 > /sys/devices/system/cpu/cpu1/online

Finally, if I boot afresh and enter system suspend, I see the system
suspend OK, but pressing the power button on either the board itself or
the attached PM342 debug board will not wake the system from sleep.