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Commit 4aed89d6 authored by Pierre Tardy's avatar Pierre Tardy Committed by Ingo Molnar
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x86, lapic-timer: Increase the max_delta to 31 bits



Latest atom socs(penwell) does not have hpet timer.

As their local APIC timer is clocked at 400KHZ, and the current
code limit their Initial Counter register to 23 bits, they
cannot sleep more than 1.34 seconds which leads to ~2 spurious
wakeup per second (1 per thread)

These SOCs support 32bit timer so we change the max_delta to at
least 31bits. So we can at least sleep for 300 seconds.

We could not find any previous chip errata where lapic would
only have 23 bit precision As powertop is suggesting to activate
HPET to "sleep longer", this could mean this problem is already
known.

Problem is here since very first implementation of lapic timer
as a clock event e9e2cdb4 [PATCH] clockevents: i386 drivers.

Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: default avatarPierre Tardy <pierre.tardy@intel.com>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Adrian Bunk <bunk@stusta.de>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
LKML-Reference: <1294327409-19426-1-git-send-email-pierre.tardy@intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 9adcc4a1
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