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Date: Wed, 25 May 2016 13:02:30 +0800
Message-ID: <CADjb_WR+ZtBf4x=JkdGhfbBNDGL=eskQp8-FADCSAzHkDLPd8w@mail.gmail.com>
Subject: Re: [PATCH][v7] x86, suspend: Save/restore extra MSR registers for suspend
From: Chen Yu <yu.chen.surf@gmail.com>
To: Len Brown <lenb@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>, Pavel Machek <pavel@ucw.cz>,
        Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@suse.de>,
        George Spelvin <linux@horizon.com>,
        "Kaszewski, Marcin" <marcin.kaszewski@intel.com>,
        Matthew Garrett <mjg59@srcf.ucam.org>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Chen Yu <yu.c.chen@intel.com>
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Hi Len,

On Wed, May 25, 2016 at 12:09 AM, Len Brown <lenb@kernel.org> wrote:
> +mjg59, who may be seeing this issue on a skylake laptop
>
> Chen-yu,
>
> Great debugging, but I think there is a more general fix possible than
> this DMI quirk.
>
> I agree that in this example, a grantley server, it seems the BIOS is
> erroneously
> returning a bogus value of MSR_IA32_THERM_CONTROL on resume from S3.
>
> But another scenario is also possible.  Consider a laptop that is resuming HOT
> and the BIOS correctly enables throttling.  If this code were invoked, it would
> restore the COLD setting.
>
> Instead, it seems to me that the ACPI processor driver should upon .resume
> check if throttling should be enabled or not, and proceed accordingly.
> That would always do the "right thing", and would not need a DMI list.
> Does that make sense?
I agree, to let the related drivers customize their restoring process
would be more robust,
and we can not only take care of boot CPU but also nonboot CPUs in this way.
I think we can add something like acpi_processor_reevaluate_tstate in the resume
hook,I'll make a double check.

thanks,
Yu