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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Sun, 3 Mar 2019 22:51:46 +0100
Message-ID: <CAJZ5v0huRALvfFBeo067dNMyUJn+Oyp8eFR3JRR+C9g7QhaekA@mail.gmail.com>
Subject: Re: [RFT][PATCH 0/2] cpufreq: intel_pstate: Handle _PPC updates on
 global turbo disable/enable
To:     Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Linux PM <linux-pm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Chen Yu <yu.c.chen@intel.com>,
        Gabriele Mazzotta <gabriele.mzt@gmail.com>
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On Sun, Mar 3, 2019 at 10:20 PM Srinivas Pandruvada
<srinivas.pandruvada@linux.intel.com> wrote:
>
> On Sun, 2019-03-03 at 18:03 +0100, Rafael J. Wysocki wrote:
> > On Fri, Mar 1, 2019 at 6:39 PM Srinivas Pandruvada
> > <srinivas.pandruvada@linux.intel.com> wrote:
> > >
> > > On Fri, 2019-03-01 at 13:43 +0100, Rafael J. Wysocki wrote:
> > > > Hi All,
> > > >
> > > > This is how I would fix the issue reported in BZ 200759 (see this
> > > > patch series
> > > > from Yu too: https://marc.info/?l=linux-pm&m=155137672924029&w=2)
> > > > .
> > > >
> > > > Patch [1/2] causes intel_pstate to update all policies if it gets
> > > > a
> > > > _PPC change
> > > > notification and sees a global turbo disable/enable change.
> > > >
> > > > Patch [2/2] makes it update cpuinfo.max_freq for all policies in
> > > > those cases.
> > > >
> > > > The patches here have not been tested yet, so testing would be
> > > > much
> > > > appreciated.
> > > >
> > > > Of course, comments are welcome too!
> > >
> > > This is the only platform, someone reported such issue.
> >
> > I don't think this matters.
> >
> > First, it doesn't mean that no other problems have this problem.
> >
> > Second, the current handling of MSR_IA32_MISC_ENABLE_TURBO_DISABLE
> > changes in intel_pstate is not sufficient if the changes is from set
> > to unset anyway.
>
> Any platform with HWP, you can't even notify of this change. So any
> platform beyond SKL is not useful.

Do you mean that HWP platforms don't supply _PPS (as a rule) and so
they don't send _PPC notifications?  Is there anything they do instead
of it?

That's fair enough, but the point is that the driver doesn't do the
right thing even if the platform does send a _PPC notification.

> Fixing is always good :-)

Well, I can only agree with that ...