From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752803AbcEIUBy (ORCPT ); Mon, 9 May 2016 16:01:54 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:54942 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752532AbcEIT5c (ORCPT ); Mon, 9 May 2016 15:57:32 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Chen Yu , "Rafael J. Wysocki" , Bin Gao , Len Brown , Thomas Gleixner , Kamal Mostafa Subject: [PATCH 4.2.y-ckt 47/59] x86/tsc: Read all ratio bits from MSR_PLATFORM_INFO Date: Mon, 9 May 2016 12:56:05 -0700 Message-Id: <1462823777-8384-48-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1462823777-8384-1-git-send-email-kamal@canonical.com> References: <1462823777-8384-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.2.8-ckt10 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Chen Yu 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 Cc: "Rafael J. Wysocki" Cc: Bin Gao Cc: Len Brown Link: http://lkml.kernel.org/r/1462505619-5516-1-git-send-email-yu.c.chen@intel.com Signed-off-by: Thomas Gleixner Signed-off-by: Kamal Mostafa --- arch/x86/kernel/tsc_msr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/tsc_msr.c b/arch/x86/kernel/tsc_msr.c index 92ae6ac..6aa0f4d 100644 --- 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; -- 2.7.4