linux-kernel - Re: [RESEND] Fast TSC calibration fails with v3.14-rc1 and later

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Message-ID: <4475332.ToUgLzVgqU@vostro.rjw.lan>
Date:	Thu, 13 Mar 2014 01:13:27 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	joeyli <jlee@...e.com>, Julian Wollrath <jwollrath@....de>,
	x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [RESEND] Fast TSC calibration fails with v3.14-rc1 and later

On Thursday, March 13, 2014 12:49:07 AM Thomas Gleixner wrote:
> On Thu, 13 Mar 2014, Rafael J. Wysocki wrote:
> > I agree, and we need to fix that for 3.14.  Patch is appended.
> 
> You beat me by a few minutes. Was about to send out the same, just
> with a more spicy changelog :)
> 
> > ---
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Subject: ACPI / init: Invoke early ACPI initialization later
> > 
> > Commit 73f7d1ca3263 (ACPI / init: Run acpi_early_init() before
> > timekeeping_init()) optimistically moved the early ACPI initialization
> > before timekeeping_init(), but that didn't work, because it broke fast
> > TSC calibration for Julian Wollrath on Thinkpad x121e (and most likely
> > for others too).  The reason is that acpi_early_init() enables the SCI
> > and that interferes with the fast TSC calibration mechanism.
> > 
> > Thus follow the original idea to execute acpi_early_init() before
> > efi_enter_virtual_mode() to help the EFI people for now and we can
> > revisit the other problem that commit 73f7d1ca3263 attempted to
> > address in the future (if really necessary).
> 
> Reviewed-by: Thomas Gleixner <tglx@...utronix.de>

Thanks!

I have a plan to push this to Linus for -rc7.

Rafael

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