linux-kernel - Re: Regression in 4.8 - CPU speed set very low

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Date:   Thu, 29 Sep 2016 22:52 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     Larry Finger <Larry.Finger@...inger.net>,
        Zhang Rui <rui.zhang@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Doug Smythies <dsmythies@...us.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: Regression in 4.8 - CPU speed set very low

On Thursday, September 29, 2016 08:56:16 AM Srinivas Pandruvada wrote:
> On Thu, 2016-09-29 at 14:19 +0200, Rafael J. Wysocki wrote:
> 
> [...]
> 
> > > My laptop was inadvertently put to sleep while I was gone. I forgot
> > > to leave a 
> > > note for my wife and she quieted the noisy cpu fan. :)
> > It looks like in 4.8-rc we made a change that caused the "high" trip
> > point to
> > be acted on.
> This high trip point we don't expose in thermal subsystem (the thermal
>  zone dump didn't show this anywhere as a trip). This is exposed by
> core-dts driver only. This is the point BIOS is supposed to act, I
> guess that's why you are seeing 50% clock modulation. 

Right.  That's SMM kicking in.

The real problem is that we get stuck at 400 MHz.

Thanks,
Rafael