linux-kernel - Re: [PATCH v3 1/3] cpufreq: mediatek: using global lock avoid race condition

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Message-ID: <2a73b5ca35692c8ffa68c9ff0df73e24a592967d.camel@mediatek.com>
Date: Fri, 21 Mar 2025 05:32:06 +0000
From: Chun-Jen Tseng (曾俊仁)
	<Chun-Jen.Tseng@...iatek.com>
To: "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>
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Subject: Re: [PATCH v3 1/3] cpufreq: mediatek: using global lock avoid race
 condition

Hi viresh,

I add a global lock related to the CCI driver.

This is because the CCI needs to obtain the frequencies of policy-0 and
policy-6 to determine its own frequency.

If policy-0 and policy-6 are set simultaneously, it may cause the CCI
to select the wrong frequency.

Therefore, I hope to change the setting flow to the following:
   policy-0 or policy-6 -> set frequency -> CCI receives notification -
> set CCI frequency

BRs,

Mark Tseng

On Fri, 2025-03-21 at 10:26 +0530, Viresh Kumar wrote:
> 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
> 
> 
> On 20-03-25, 08:22, Chun-Jen Tseng (曾俊仁) wrote:
> > The struct mtk_cpu_dvfs_info instance is per-policy and the
> > reg_lock is
> > also in this structure. when I have two "policy-0" and "policy-6"
> > use
> > the same mtk_cpufreq_set_target() function but the info->reg_lock
> > is from 2 instance(policy-0 and policy-6). when the policy-0 and
> > policy-6 call set_target target, the mutex_lock is locked by per-
> > policy. So, I change to global lock avoid per-policy lock.
> 
> Yes, that's what you are doing. I am asking why a global lock is
> required here ?
> I think the per-policy lock is all you need.
> 
> --
> viresh