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

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Message-ID: <1394447253.2979.12.camel@x220>
Date:	Mon, 10 Mar 2014 11:27:33 +0100
From:	Paul Bolle <pebolle@...cali.nl>
To:	Julian Wollrath <jwollrath@....de>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND] Fast TSC calibration fails with v3.14-rc1 and later

On Mon, 2014-03-10 at 11:04 +0100, Julian Wollrath wrote:
> on a Thinkpad x121e (AMD E-450 APU) with version 3.13.5 and earlier of
> the kernel I get:
> [...]
> [    0.000000] tsc: Fast TSC calibration using PIT
> [    0.001000] tsc: Detected 1646.619 MHz processor
> [    0.000004] Calibrating delay loop (skipped), value calculated using
> timer frequency.. 3293.23 BogoMIPS (lpj=1646619)
> [...]
> 
> 
> but starting with v3.14-rc1 the fast TSC calibration fails:
> [...]
> [    0.000000] tsc: Fast TSC calibration failed
> [    0.000000] tsc: PIT calibration matches HPET. 1 loops
> [    0.000000] tsc: Detected 1646.490 MHz processor
> [...]
> 
> If you need more information, please do not hesitate to ask.

I submitted a patch to downgrade the "Fast TSC calibration failed"
message to KERN_INFO level, see https://lkml.org/lkml/2012/9/26/131 .
That patch was basically ignored. I've carried it locally ever since.

So the error need not be v3.14-rc1 specific. But perhaps something
changed in v3.14-rc1 that makes it easier to trigger that error. I
haven't checked.

(I wrote some notes on this issue in
https://lkml.org/lkml/2012/9/24/221 , perhaps they might be of help.)


Paul Bolle

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