Messages in this thread | | | Subject | Re: [PATCH] i386: trust the PM-Timer calibration of the local APIC timer | From | Thomas Gleixner <> | Date | Sun, 18 Mar 2007 09:45:26 +0100 |
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On Sun, 2007-03-18 at 00:12 -0800, Andrew Morton wrote: > On Sat, 17 Mar 2007 01:04:56 +0100 Thomas Gleixner <tglx@linutronix.de> wrote: > > > When PM-Timer is available for local APIC timer calibration we can skip > > the verification of the calibrated time value. The resulting error is > > quite small on a bunch of evaluated platforms and is less harming than > > the observed false positives. > > > > We need to keep the verification on systems, which have no PM-Timer to > > avoid bogus local APIC timer calibrations in the range of factor 2-10, > > which can be observed when swicthing off the PM-timer support in the > > kernel configuration. > > > > The wrong calibration values are probably caused by SMM code trying to > > emulate a PS/2 keyboard from a (maybe connected or not) USB keyboard. > > This prohibits the accurate delivery of PIT interrupts, which are used > > to calibrate the local APIC timer. Unfortunately we have no way to > > disable this BIOS misfeature in the early boot process. > > > > Add also the dropped cpu_relax() back to the wait loops. > > Is this a for-2.6.21 thing?
Yes please. The false positives of the original calibration are annoying.
tglx
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