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From: Thomas Gleixner <tglx@linutronix.de>
To: "Jan H. Schönherr" <jan@schnhrr.de>
Cc: bp@alien8.de, mingo@redhat.com, x86@kernel.org,
	pmenzel@molgen.mpg.de, Thomas.Lendacky@amd.com, hpa@zytor.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] x86/tsc: Allow quick PIT calibration despite interruptions
Date: Tue, 29 Jan 2019 23:28:45 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.21.1901292327090.1950@nanos.tec.linutronix.de> (raw)
In-Reply-To: <5C50558B.8060405@schnhrr.de>

[-- Attachment #1: Type: text/plain, Size: 802 bytes --]

On Tue, 29 Jan 2019, Jan H. Schönherr wrote:

> Am 29.01.2019 um 11:23 schrieb Jan H. Schönherr:
> > +calibrate:
> > +	/*
> > +	 * Extrapolate the error and fail fast if the error will
> > +	 * never be below 500 ppm.
> > +	 */
> > +	if (d1 + d1 >= (delta * MAX_QUICK_PIT_ITERATIONS) >> 11) {
> > +		pr_info("Fast TSC calibration failed (wouldn't work)\n");
> > +		return 0;
> > +	}
> 
> I messed this check up. "delta" is not the actual tsc delta between the
> first two successful reads at this point.
> 
> (If it were, it might also correspond to more than one iteration; not
> sure if we care about that aspect, though.)

I rather go for correct and if only for the reason that me/you/whoelse
doesn't have to scratch the head for an hour when looking at this half a
year from now.

Thanks,

	tglx

  parent reply	other threads:[~2019-01-29 22:29 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-29 10:23 [PATCH 0/2] Fix TSC issues on (some) AMD Ryzen based systems Jan H. Schönherr
2019-01-29 10:23 ` [PATCH 1/2] x86/tsc: Allow quick PIT calibration despite interruptions Jan H. Schönherr
     [not found]   ` <5C50558B.8060405@schnhrr.de>
2019-01-29 22:28     ` Thomas Gleixner [this message]
2019-02-12 11:57       ` Thomas Gleixner
2019-02-14 21:48         ` Jan H. Schönherr
2019-01-29 10:23 ` [PATCH 2/2] cpu/hotplug: Unfreeze sibling CPU first on resume from S3 Jan H. Schönherr
2019-01-29 23:02   ` Thomas Gleixner
2019-01-29 19:33 ` [PATCH 0/2] Fix TSC issues on (some) AMD Ryzen based systems Paul Menzel
2019-01-29 19:37   ` Paul Menzel
2019-01-29 22:31     ` Thomas Gleixner

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