x86, tsc: Add static (MSR) TSC calibration on Intel Atom SoCs

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On SoCs that have the calibration MSRs available, either there is no
PIT, HPET or PMTIMER to calibrate against, or the PIT/HPET/PMTIMER is
driven from the same clock as the TSC, so calibration is redundant and
just slows down the boot.

TSC rate is caculated by this formula:
<maximum core-clock to bus-clock ratio> * <maximum resolved frequency>
The ratio and the resolved frequency ID can be obtained from MSR.
See Intel 64 and IA-32 System Programming Guid section 16.12 and 30.11.5
for details.

Signed-off-by: Bin Gao <bin.gao@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/n/tip-rgm7xmg7k6qnjlw3ynkcjsmh@git.kernel.org

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Bin Gao 2013-10-21 09:16:33 -07:00 • committed by H. Peter Anvin

parent 4618441536

commit 7da7c15613

4 changed files with 139 additions and 1 deletions

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3

arch/x86/include/asm/tsc.h

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2

arch/x86/kernel/Makefile

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10

arch/x86/kernel/tsc.c

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125

arch/x86/kernel/tsc_msr.c

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