[RFC PATCH v4 1/4] cpuidle: Add time keeping and irq enabling

[Turquette, Mike]

On Sat, Feb 4, 2012 at 5:36 PM, Colin Cross <ccross at google.com> wrote:
> On Sat, Feb 4, 2012 at 2:06 PM, Turquette, Mike <mturquette at ti.com> wrote:
>> On Sat, Feb 4, 2012 at 11:02 AM, Colin Cross <ccross at google.com> wrote:
>>> What's the point of the pre_enter call?  This seems very similar to
>>> the prepare call that was removed in 3.2.  Drivers can already demote
>>
>> Hi Colin,
>>
>> I asked Rob to re-introduce the .prepare callback (not .pre_enter).
>>
>> The short version of why I requested this is so that I can experiment
>> with modifying wake-up latency and theshold values dynamically based
>> on PM QoS constraints.  For an OMAP-specific example, I'd like to see
>> our C-states no longer model both MPU and CORE power domains, and
>> instead only model the MPU.  Then when entering idle the PM QoS
>> constraints against the CORE power domain's wake-up latency can be
>> considered in the .prepare callback which will affect the C-state
>> parameters as well as program the CORE low power target state.
>
> prepare makes sense to adjust latencies, as long as it is not used for
> state demotion as well.

Latency adjustment is the plan.  State demotion is not.

Rob,

If you cook up another version of this series feel free to drop
.pre_enter.  It would be nice if you re-introduced .prepare as per our
original discussion but if that's a roadblock then you can forget that
point too and I'll take a crack at it later.

Regards,
Mike

>> .pre_enter isn't really right for the above case so I'm happy for it
>> to be dropped, but I'll probably re-introduce something like .prepare
>> in the future...
>>
>> Regards,
>> Mike
>>
>>> the target state in their enter call.  The only thing you do between
>>> pre_enter and enter is trace and account for the time.  Is there some
>>> long call you don't want included in the idle time?  Some
>>> documentation would help, and you need to very clearly define the
>>> semantics of when post_enter gets called when pre_enter or enter
>>> return errors.
>>>
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