[PATCH 7/7] ARM: tegra30: cpuidle: add LP2 driver for CPU0

[Colin Cross]

On Fri, Oct 12, 2012 at 1:24 AM, Joseph Lo <josephl at nvidia.com> wrote:
> On Fri, 2012-10-12 at 15:54 +0800, Shawn Guo wrote:
>> On Thu, Oct 11, 2012 at 09:48:45AM -0700, Colin Cross wrote:
>> > As is, coupled cpuidle will work on Tegra30, but it will unnecessarily
>> > wake up the secondary cpus during the transitions to off and back on
>> > again.  Those cpus will immediately go back to single-cpu LP2,
>>
>> I'm sure coupled cpuidle will work like that.  We have the following
>> code at the end of  cpuidle_enter_state_coupled() to wait until all
>> coupled cpus have exited idle.
>>
>>         while (!cpuidle_coupled_no_cpus_ready(coupled))
>>                 cpu_relax();
>>
>> The cpu woken up during the transitions will just loop there until all
>> other 3 cpus exit from idle function.
>>
>
> Did this a good idea if the CPU was been woken up from an interrupt but
> it still needed to wait all other CPUs been woken up then it could
> handle the interrupt?

Each cpu enables its local interrupts between when it clears it's
ready flag and when it enters the loop above, so it will already be
handling interrupts.