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[PATCH 3.14 16/23] x86/tsc: Read all ratio bits from MSR_PLATFORM_INFO

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3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chen Yu <yu.c.chen@intel.com>

commit 886123fb3a8656699dff40afa0573df359abeb18 upstream.

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: 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kernel/tsc_msr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/tsc_msr.c
+++ b/arch/x86/kernel/tsc_msr.c
@@ -92,7 +92,7 @@ unsigned long try_msr_calibrate_tsc(void
 
 	if (freq_desc_tables[cpu_index].msr_plat) {
 		rdmsr(MSR_PLATFORM_INFO, lo, hi);
-		ratio = (lo >> 8) & 0x1f;
+		ratio = (lo >> 8) & 0xff;
 	} else {
 		rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
 		ratio = (hi >> 8) & 0x1f;

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[PATCH 3.14 00/23] 3.14.69-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 21/23] iio: ak8975: Fix NULL pointer exception on early interrupt Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 07/23] lpfc: fix misleading indentation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 04/23] ipvs: correct initial offset of Call-ID header search in SIP persistence engine Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 22/23] Input: ads7846 - correct the value got from SPI Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 01/23] compiler-gcc: integrate the various compiler-gcc[345].h files Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
    Re: [PATCH 3.14 01/23] compiler-gcc: integrate the various  compiler-gcc[345].h files Jiri Slaby <jslaby@suse.cz> - 2016-05-11 11:30 +0200
  [PATCH 3.14 20/23] USB: serial: cp210x: add Straizona Focusers device ids Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 16/23] x86/tsc: Read all ratio bits from MSR_PLATFORM_INFO Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 23/23] powerpc: scan_features() updates incorrect bits for REAL_LE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 19/23] USB: serial: cp210x: add ID for Link ECU Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 12/23] batman-adv: Check skb size before using encapsulated ETH+VLAN header Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 10/23] Input: zforce_ts - fix dual touch recognition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 09/23] ARM: SoCFPGA: Fix secondary CPU startup in thumb2 kernel Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:00 +0200
  [PATCH 3.14 18/23] ACPICA: Dispatcher: Update thread ID for recursive method calls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 15/23] MAINTAINERS: Remove asterisk from EFI directory names Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 11/23] proc: prevent accessing /proc/<PID>/environ until its ready Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 08/23] tracing: Dont display trigger file for events that cant be enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 17/23] x86/sysfb_efi: Fix valid BAR address range check Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 05/23] nbd: ratelimit error msgs after socket close Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 02/23] compiler-gcc: disable -ftracer for __noclone functions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  Re: [PATCH 3.14 00/23] 3.14.69-stable review Guenter Roeck <linux@roeck-us.net> - 2016-05-09 15:30 +0200
  Re: [PATCH 3.14 00/23] 3.14.69-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-05-09 21:50 +0200

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