linux-kernel - Re: [PATCH v2 3/3] cpufreq: Update set_boost callbacks to rely on boost_freq

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Message-ID: <CAJZ5v0hZMSWxd6u0ZpPosDu9j0ibYeGyqRRqnaiVBNcA1kmPXA@mail.gmail.com>
Date: Tue, 13 Jan 2026 13:20:26 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Pierre Gondois <pierre.gondois@....com>, "zhenglifeng (A)" <zhenglifeng1@...wei.com>, 
	linux-kernel@...r.kernel.org, Christian Loehle <christian.loehle@....com>, 
	Ionela Voinescu <ionela.voinescu@....com>, Jie Zhan <zhanjie9@...ilicon.com>, 
	Huang Rui <ray.huang@....com>, "Gautham R. Shenoy" <gautham.shenoy@....com>, 
	Mario Limonciello <mario.limonciello@....com>, Perry Yuan <perry.yuan@....com>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 3/3] cpufreq: Update set_boost callbacks to rely on boost_freq_req

On Tue, Jan 13, 2026 at 2:30 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 12-01-26, 16:02, Pierre Gondois wrote:
> > In:
> > cpufreq_set_policy()
> > \-cpufreq_driver->verify(&new_data)
> >   \-cpufreq_verify_within_cpu_limits()
> >
> > the requested min/max values are clamped wrt the cpuinfo.[min|max]_freq.
> > However this clamping happens after the QoS constraints have been
> > aggregated. This means that if a CPU has:
> > - min = 100.000 kHz
> > - max = 1.000.000 kHz
> > - boost = 1.200.000 kHz
> >
> > With boost enabled, the user requests:
> > - scaling_min: 1.100.000
> > - scaling_max: 1.200.000
> >
> > If boost is disabled, we will have:
> > policy->min == policy->max == 1.000.000
> > without notifying anybody.
> >
> > Ideally I assume it would be better to prevent the user from disabling
> > boost without first asking to update the scaling_[min|max] frequencies,
> > or at least detecting this case and have a warning message.
>
> I don't think this is a problem and doesn't really need special care.
> It is the user who is disabling the boost feature, its okay to force
> set to clamped values.
>
> > Please let me know if you prefer not adding the new qos constraint,
> > I ll try harder not to have it if yes.
>
> But even with that (the issue pointed earlier not being a problem), I
> think a new constraint for boost does make the code cleaner and easy
> to follow.
>
> Rafael ?

I agree.