Re: [PATCH] i386: trust the PM-Timer calibration of the local APIC timer
On Sun, 2007-03-18 at 00:12 -0800, Andrew Morton wrote: > On Sat, 17 Mar 2007 01:04:56 +0100 Thomas Gleixner <[EMAIL PROTECTED]> 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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] i386: trust the PM-Timer calibration of the local APIC timer
On Sat, 17 Mar 2007 01:04:56 +0100 Thomas Gleixner <[EMAIL PROTECTED]> 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? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] i386: trust the PM-Timer calibration of the local APIC timer
Thomas Gleixner <[EMAIL PROTECTED]> writes: > 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. Looks good to me. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] i386: trust the PM-Timer calibration of the local APIC timer
* Thomas Gleixner <[EMAIL PROTECTED]> 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. > > Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]> Acked-by: Ingo Molnar <[EMAIL PROTECTED]> Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
