Messages in this thread |  | | | Date | Sun, 18 Mar 2007 00:12:35 -0800 | | From | Andrew Morton <> | | Subject | Re: [PATCH] i386: trust the PM-Timer calibration of the local APIC timer |
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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.
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