linux-kernel - Re: [PATCH][v3] cpufreq: intel_pstate: Get percpu max freq via HWP MSR register if available

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Message-ID: <CAJZ5v0igG=kyL7zFrvCLcMAE7uLzaB-MC8fZBxBX17WNTpR5Cg@mail.gmail.com>
Date:   Tue, 12 Jan 2021 19:46:31 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][v3] cpufreq: intel_pstate: Get percpu max freq via HWP
 MSR register if available

On Tue, Jan 12, 2021 at 4:00 PM Chen Yu <yu.c.chen@...el.com> wrote:
>
> On Tue, Jan 12, 2021 at 02:52:50PM +0100, Rafael J. Wysocki wrote:
> > On Tue, Jan 12, 2021 at 6:19 AM Chen Yu <yu.c.chen@...el.com> wrote:
> > >
> > > Currently when turbo is disabled(either by BIOS or by the user), the
> > > intel_pstate driver reads the max non-turbo frequency from the package-wide
> > > MSR_PLATFORM_INFO(0xce) register. However on asymmetric platforms it is
> > > possible in theory that small and big core with HWP enabled might have
> > > different max non-turbo cpu frequency, because the MSR_HWP_CAPABILITIES
> > > is percpu scope according to Intel Software Developer Manual.
> > >
> > > The turbo max freq is already percpu basis in current code, thus make
> > > similar change to the max non-turbo frequency as well.
> > >
> > > Reported-by: Wendy Wang <wendy.wang@...el.com>
> > > Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> > > ---
> > > v2: Per Srinivas' suggestion, avoid duplicated assignment of max_pstate.
> > > v3: Per Rafael's suggestion, do not add new argument in intel_pstate_get_hwp_max()
> > >     to avoid redundant local vars.
> > >     Per Srinivas' suggestion, refined the commit log to reflect the 'non-turbo'
> > >     max frequency.
> >
> > Looks good now, thanks!
> >
> > Is it needed in -stable and if so, which -stable series should it go into?
> >
> Yes, I think so, it should be
> Cc: stable@...r.kernel.org # 4.18+
> as the HWP reading turbo frequency was firstly introduced in v4.18-rc2 and it
> was easier to be applied.
> BTW, this patch is on top of your previous patch set on intel_pstate clean up:
> https://patchwork.kernel.org/project/linux-pm/list/?series=410797

OK, applied (with a few minor edits in the subject and changelog) as
5.12 material along with those patches , thanks!