linux-kernel - Re: tsc: Fast TSC calibration failed with AMD B350M/Ryzen 3 2200G

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Message-ID: <alpine.DEB.2.21.1901112141480.1661@nanos.tec.linutronix.de>
Date:   Fri, 11 Jan 2019 21:43:37 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
cc:     x86@...nel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: tsc: Fast TSC calibration failed with AMD B350M/Ryzen 3 2200G

Paul,

On Mon, 7 Jan 2019, Paul Menzel wrote:
> On 01/07/19 16:24, Thomas Gleixner wrote:
> >> Linux 4.19.13 from Debian Sid/unstable logs the message below on the board MSI
> >> MS-7A37/B350M MORTAR with the processor AMD Ryzen 3 2200G.
> >>
> >> As a result, the early time stamps do not seem to be working.
> > 
> >>> [    0.000000] DMI: Micro-Star International Co., Ltd. MS-7A37/B350M MORTAR (MS-7A37), BIOS 1.I0 11/06/2018
> >>> [    0.000000] tsc: Fast TSC calibration failed
> > 
> > And the further boot log says:
> > 
> > [    0.036000] tsc: Unable to calibrate against PIT
> > [    0.036000] tsc: using HPET reference calibration
> > [    0.036000] tsc: Detected 3500.117 MHz processor
> > 
> > So the quick calibration in early boot fails because the PIT seems not to
> > do what the kernel expects. Nothing we can cure :(
> 
> I see. Can AMD confirm that this is the expected behavior? If yes, should
> the fast TSC calibration be skipped on these devices?

It should work and we really don't want to add cpu family/model based
decisions whether we invoke something or not. Those tables are stale before
they hit mainline.

Thanks,

	tglx