Re: [PATCH V4 5/5] ARM: tegra20: cpuidle: apply coupled cpuidle for powered-down mode

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

On 01/16/2013 11:55 AM, Colin Cross wrote:
> On Wed, Jan 16, 2013 at 12:11 AM, Joseph Lo <josephl-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> wrote:
>> The "powered-down" cpuidle mode of Tegra20 needs the CPU0 be the last one
>> core to go into this mode before other core. The coupled cpuidle framework
>> can help to sync the MPCore to coupled state then go into "powered-down"
>> idle mode together. The driver can just assume the MPCore come into
>> "powered-down" mode at the same time. No need to take care if the CPU_0
>> goes into this mode along and only can put it into safe idle mode (WFI).
>>
>> The powered-down state of Tegra20 requires power gating both CPU cores.
>> When the secondary CPU requests to enter powered-down state, it saves
>> its own contexts and then enters WFI for waiting CPU0 in the same state.
>> When the CPU0 requests powered-down state, it attempts to put the secondary
>> CPU into reset to prevent it from waking up. Then power down both CPUs
>> together and power off the cpu rail.
>>
>> Be aware of that, you may see the legacy power state "LP2" in the code

Colin, since you only raised a few small issues on this series, does
that mean you're OK with it once those issues are fixed?

Joseph, we'll be merging Tegra114 in the near future. How will this
patch series affect Tegra114? Will the cpuidle driver simply fail to
register on Tegra114 (which would be fine until we explicitly add
support), or would we need to disable cpuidle in Kconfig to get a
working Tegra114 kernel. Does this patch series affect the answer to the
previous question? Thanks.