linux-kernel - Re: [PATCH 1/6] cpufreq: acpi: Don't enable boost on policy exit

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Message-ID: <20250424071503.2uhc4k3jxy7x5mo2@vireshk-i7>
Date: Thu, 24 Apr 2025 12:45:03 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Lifeng Zheng <zhenglifeng1@...wei.com>, linux-pm@...r.kernel.org,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Nicholas Chin <nic.c3.14@...il.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] cpufreq: acpi: Don't enable boost on policy exit

On 23-04-25, 16:14, Rafael J. Wysocki wrote:
> Even after commit 2b16c631832d, the code removed by this patch does a
> useful thing.  Namely, it clears the boost-disable bit in the MSR so
> that the offline CPU doesn't prevent online CPUs from getting the
> boost (in case the boost settings change after it has been taken
> offline).

I didn't understand this part earlier (and even now). How does a CPU
with boost-disabled, prevents others from boosting ? I have tried
looking at git logs, and still don't understand it :(

Also, IIUC this and the boost-enabling at init() only happens for one
CPU in a policy, as init() and exit() are only called for the first
and last CPU of a policy. So if a policy has multiple CPUs, we aren't
touching boost states of other CPUs at init/exit.

And yes, this patch isn't mandatory at all for the 

> Moreover, without the $subject patch, the change made by the next one
> will cause the boost setting in the MSR to get back in sync with
> policy->boost_enabled during online AFAICS, so why exactly is the
> $subject patch needed?

Right, this is merely a cleanup patch and isn't really required for
the next patch to make it work.

-- 
viresh