linux-kernel - Re: [RFT][PATCH 0/2] cpufreq: intel_pstate: Handle _PPC updates on global turbo disable/enable

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Date:   Sat, 2 Mar 2019 18:30:08 +0800
From:   Yu Chen <yu.c.chen@...el.com>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Gabriele Mazzotta <gabriele.mzt@...il.com>
Subject: Re: [RFT][PATCH 0/2] cpufreq: intel_pstate: Handle _PPC updates on
 global turbo disable/enable

On Fri, Mar 01, 2019 at 09:39:27AM -0800, Srinivas Pandruvada 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.
> Can we solve this by some udev rules and offline/online cpu 1-3 on
> power source change?
>
Sound reasonable, we can deal with this BIOS problem in user space
too. But if cpu0 could not be offline, how could cpu0's policy
be updated?

Thanks,
Yu

> There are examples of changing governors on power source change.
> https://bbs.archlinux.org/viewtopic.php?id=207186
> 
> Here instead of changing governor just
> echo 0 > /sys/devices/system/cpu/cpu1/online
> echo 1 > /sys/devices/system/cpu/cpu1/online
> echo 0 >
> /sys/devices/system/cpu/cpu2/online
> echo 1 >
> /sys/devices/system/cpu/cpu2/online
> echo 0 >
> /sys/devices/system/cpu/cpu3/online
> echo 1 >
> /sys/devices/system/cpu/cpu3/online
> 
> Thanks,
> Srinivas
> 
> > 
> > Thanks,
> > Rafael
> > 
>