linux-kernel - Re: [PATCH v2] cpufreq/cppc: Take policy->cur into judge when set target

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Message-ID: <20240530055624.quutkzdd44l3oevc@vireshk-i7>
Date: Thu, 30 May 2024 11:26:24 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Riwen Lu <luriwen@...mail.com>,
	Ionela Voinescu <ionela.voinescu@....com>,
	Beata Michalska <beata.michalska@....com>,
	Hoan Tran <hotran@....com>
Cc: rafael@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Riwen Lu <luriwen@...inos.cn>
Subject: Re: [PATCH v2] cpufreq/cppc: Take policy->cur into judge when set
 target

Cc'ing few more people.

On 30-05-24, 09:06, Riwen Lu wrote:
> 在 2024/5/29 15:12, Viresh Kumar 写道:
> > On 29-05-24, 14:53, Riwen Lu wrote:
> > > Yes, you are right， I didn't think it through. In this circumstance, the
> > > policy->cur is the highest frequency, desired_perf converted from
> > > target_freq is the same with cpu_data->perf_ctrls.desired_perf which
> > > shouldn't.
> > 
> > Please investigate more and see where the real problem is.
> > 
> The boot CPU's frequency would be configured to the highest perf when
> powered on from S3 even though the policy governor is powersave.
> 
> In cpufreq resume process, the booting CPU's new_freq obtained via .get() is
> the highest frequency, while the policy->cur and
> cpu->perf_ctrls.desired_perf are in the lowest level(powersave governor).
> Causing the warning: "CPU frequency out of sync:", and set policy->cur to
> new_freq. Then the governor->limits() calls cppc_cpufreq_set_target() to
> configures the CPU frequency and returns directly because the desired_perf
> converted from target_freq and cpu->perf_ctrls.desired_perf are the same and
> both are the lowest_perf.
> 
> The problem is that the cpu->perf_ctrls.desired_perf is the lowest_perf but
> it should be the highest_perf.
> 
> In my opinion, desired_perf and cpu->perf_ctrls.desired_perf represent the
> target_freq and policy->cur respectively. Since target_freq and policy->cur
> have been compared in __cpufreq_driver_target(), there's no need to compare
> desired_perf and cpu->perf_ctrls.desired_perf again in
> cppc_cpufreq_set_target().
> So, maybe we can remove the following logic in cppc_cpufreq_set_target().
> /* Return if it is exactly the same perf */
> if (desired_perf == cpu_data->perf_ctrls.desired_perf)
> 	return ret;

This is what I was thinking as well yesterday.

-- 
viresh