Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support

From: Sudeep Holla
Date: Thu Jul 13 2017 - 10:06:27 EST

On 13/07/17 14:08, Dietmar Eggemann wrote:
> On 13/07/17 13:40, Sudeep Holla wrote:
>> On 11/07/17 16:21, Dietmar Eggemann wrote:
>>> On 11/07/17 07:39, Viresh Kumar wrote:
>>>> On 10-07-17, 14:46, Rafael J. Wysocki wrote:
> [...]
>>> Like I said in the other email, since for (future)
>>> arm/arm64 fast-switch driver, the return value of
>>> cpufreq_driver->fast_switch() does not give us the information that the
>>> frequency value did actually change, we have to implement
>> I was under the impression that we strictly don't care about that
>> information when I started exploring the fast_switch with the standard
>> firmware interface on ARM platforms(until if and when ARM provides an
>> instruction to achieve that).
>> If f/w failed to change the frequency, will that be not corrected in the
>> next sample or instance. I would like to know the impact of absence of
>> such notifications.
> In the meantime we agreed that we have to invoke frequency invariance
> from within the cpufreq driver.
> For a fast-switch driver I would have to put the call to
> arch_set_freq_scale() somewhere where I know that the frequency has been
> set.
> Without a notification (from the firmware) that the frequency has been
> set, I would have to call arch_set_freq_scale() somewhere in the
> driver::fast_switch() call assuming that the frequency has been actually
> set.

Yes, that's what I was thinking too.