x86/tsc: Read all ratio bits from MSR_PLATFORM_INFO
authorChen Yu <yu.c.chen@intel.com>
Fri, 6 May 2016 03:33:39 +0000 (11:33 +0800)
committerThomas Gleixner <tglx@linutronix.de>
Fri, 6 May 2016 09:50:50 +0000 (11:50 +0200)
commit886123fb3a8656699dff40afa0573df359abeb18
treef3bf6d9ad49babf098f3f3142a34d79d1744b848
parent08914f436bdd2ed60923f49cbc402307aba20fe4
x86/tsc: Read all ratio bits from MSR_PLATFORM_INFO

Currently we read the tsc radio: ratio = (MSR_PLATFORM_INFO >> 8) & 0x1f;

Thus we get bit 8-12 of MSR_PLATFORM_INFO, however according to the SDM
(35.5), the ratio bits are bit 8-15.

Ignoring the upper bits can result in an incorrect tsc ratio, which causes the
TSC calibration and the Local APIC timer frequency to be incorrect.

Fix this problem by masking 0xff instead.

[ tglx: Massaged changelog ]

Fixes: 7da7c1561366 "x86, tsc: Add static (MSR) TSC calibration on Intel Atom SoCs"
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: stable@vger.kernel.org
Cc: Bin Gao <bin.gao@intel.com>
Cc: Len Brown <lenb@kernel.org>
Link: http://lkml.kernel.org/r/1462505619-5516-1-git-send-email-yu.c.chen@intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
arch/x86/kernel/tsc_msr.c