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The local apic timer calibration has two problem cases: 1. The calibration is based on readout of the PIT/HPET timer to detect the wrap of the periodic tick. It happens that a box gets stuck in the calibration loop due to a PIT with a broken readout function. 2. CoreDuo boxen show a sporadic PIT runs too slow defect, which results in a wrong lapic calibration. The PIT goes back to normal operation once the lapic timer is switched to periodic mode. Both are existing and unfixed problems in the current upstream kernel and prevent certain laptops and other systems from booting Linux. Rework the code to address both problems: - Make the calibration interrupt driven. This removes the wait_timer_tick magic hackery from lapic.c and time_hpet.c. The clockevents framework allows easy substitution of the global tick event handler for the calibration. This is more accurate than monitoring jiffies. At this point of the boot process, nothing disturbes the interrupt delivery, so the results are very accurate. - Verify the calibration against the PM timer, when available by using the early access function. When the measured calibration period is outside of an one percent window, then the lapic timer calibration is adjusted to the pm timer result. - Verify the calibration by running the lapic timer with the calibration handler. Disable lapic timer in case of deviation. This also removes the "synchronization" of the local apic timer to the global tick. This synchronization never worked, as there is no way to synchronize PIT(HPET) and local APIC timer. The synchronization by waiting for the tick just alignes the local APIC timer for the first events, but later the events drift away due to the different clocks. Removing the "sync" is just randomizing the asynchronous behaviour at setup time. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Zachary Amsden <zach@vmware.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Rohit Seth <rohitseth@google.com> Cc: Andi Kleen <ak@suse.de> Cc: john stultz <johnstul@us.ibm.com> Cc: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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