Re: [PATCH V4 07/14] cpufreq: mediatek: Add .get function

From: Viresh Kumar
Date: Mon Apr 25 2022 - 06:01:48 EST

On 25-04-22, 17:34, Rex-BC Chen wrote:
> We found that the pulses of cpu voltage could be observed when
> frequency is fixed (scaling_max_freq == scaling_min_freq) if using
> cpufreq_generic_get as '.get' callback in MT8186.
> cpufreq framework will constantly (~ 1 sec) call 'update' if the policy

Which function gets called here in that case ? I would expect
cpufreq_driver_target() to not make a call to MTK driver in that case, after it
finds that new and old frequency are same (it will check the corresponding freq
from cpufreq table).

> frequency is NOT equal to hardware frequency in
> cpufreq_verify_current_freq.
> The problem is that there might be a tiny difference between the policy
> frequency and the hardware frequency even they are very close.
> e.g. policy frequency is 500,000,000 Hz however, hardware frequency is
> 499,999,726 Hz for MT8186 opp15.
> To prevent the voltage pulses, we currently use the software cached
> values as you pointed out.
> I wonder is it possible to add a tolerence for checking difference
> between policy frequency and hardware frequency in cpufreq framework so
> that we can use cpufreq_generic_get as callback without pulse issue.
> Or any suggestion would be appreciated.