linux-kernel - Re: [PATCH v1 2/2] cpufreq: mediatek: Fixed cpufreq has 2 policy will cause concurrency

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Message-ID: <20241001064351.vpahvdwzmvjblnd7@vireshk-i7>
Date: Tue, 1 Oct 2024 12:13:51 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Mark Tseng <chun-jen.tseng@...iatek.com>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org,
	Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v1 2/2] cpufreq: mediatek: Fixed cpufreq has 2 policy
 will cause concurrency

On 13-09-24, 18:39, Mark Tseng wrote:
> mtk_cpufreq_set_target() is re-enter function but the mutex lock decalre
> in mtk_cpu_dvfs_info structure for each policy. It should change to
> global variable for critical session avoid policy get wrong OPP.

I am not sure I understood the problem well. Can you explain clearly
why the current locking doesn't work with details call chain ?

It is normally okay to have per-policy locks otherwise. Are there any
common resources being used between policies that need locking ?

> SoC with CCI architecture should set transition_delay to 10 ms
> because cpufreq need to call devfreq notifier in async mode. if delay
> less than 10ms may get wrong OPP-level in CCI driver.
> 
> Add CPUFREQ_ASYNC_NOTIFICATION flages for cpufreq policy because some of
> process will get CPU frequency by cpufreq sysfs node. It may get wrong
> frequency then call cpufreq_out_of_sync() to fixed frequency.

Don't do so much in a single commit. Separate commits for each logical
change so they can be reviewed well. Also don't send cpufreq along
with devfreq changes, unless they are dependent on each other.

-- 
viresh