Re: [PATCH v2] x86/tsc: Set X86_FEATURE_TSC_RELIABLE to skip refined calibration
From: Thomas Gleixner
Date: Wed Oct 12 2016 - 03:56:51 EST
On Tue, 11 Oct 2016, Bin Gao wrote:
> On Fri, Aug 26, 2016 at 12:14:58PM +0200, Thomas Gleixner wrote:
> The Linux kernel does think a reliable calibration implies the reliability (i.e.
> no watchdog required). I'm posting some code pieces to explain.
I know that and I know exactly how all that works. And I certainly did not
ask for an explanation of the current state of affairs. Here is what I
> > Second thoughts. We should seperate the calibration aspect from the reliablity
> > aspect.
> > If a MSR/CPUID readout provides reliable calibration then this does not tell
> > us about the reliablity (i.e. no watchdog required). So having two flags for
> > this - and sure you can set both on those SoCs is the proper solution.
In other words: I want to have two seperate flags:
1) FEATURE_KNOWN_FREQUENCY - Grab the frequency from CPUID/MSR or whatever
and skip the whole calibration thing
2) FEATURE_RELIABLE - Do not invoke the watchdog