Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate()

[Thomas Gleixner]

On Thu, 21 May 2015, Adrian Hunter wrote:

> If it takes longer than 12us to read the PIT counter lsb/msb,
> then the error margin will never fall below 500ppm within 50ms,
> and Fast TSC calibration will always fail.

So finally the legacy PIT emulation takes longer than the 30 years old
hardware implementation. Progress!
 
> This patch detects when that will happen and switches to using
> a slightly different algorithm that takes advantage of the PIT's
> latch comand.

Is there really no smarter way to figure out the TSC frequency on
modern systems?

Thanks,

	tglx
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