linux-kernel - [tip:x86/urgent] x86/tsc: Add the Intel Denverton Processor to native_calibrate

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Message-ID: <tip-695085b4bc7603551db0b3da897b8bf9893ca218@git.kernel.org>
Date:   Sat, 14 Jan 2017 01:58:35 -0800
From:   tip-bot for Len Brown <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     torvalds@...ux-foundation.org, len.brown@...el.com, hpa@...or.com,
        peterz@...radead.org, tglx@...utronix.de, mingo@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip:x86/urgent] x86/tsc: Add the Intel Denverton Processor to
 native_calibrate_tsc()

Commit-ID:  695085b4bc7603551db0b3da897b8bf9893ca218
Gitweb:     http://git.kernel.org/tip/695085b4bc7603551db0b3da897b8bf9893ca218
Author:     Len Brown <len.brown@...el.com>
AuthorDate: Fri, 13 Jan 2017 01:11:18 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sat, 14 Jan 2017 09:30:37 +0100

x86/tsc: Add the Intel Denverton Processor to native_calibrate_tsc()

The Intel Denverton microserver uses a 25 MHz TSC crystal,
so we can derive its exact [*] TSC frequency
using CPUID and some arithmetic, eg.:

  TSC: 1800 MHz (25000000 Hz * 216 / 3 / 1000000)

[*] 'exact' is only as good as the crystal, which should be +/- 20ppm

Signed-off-by: Len Brown <len.brown@...el.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/306899f94804aece6d8fa8b4223ede3b48dbb59c.1484287748.git.len.brown@intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/tsc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index be3a49e..e41af59 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -694,6 +694,7 @@ unsigned long native_calibrate_tsc(void)
 			crystal_khz = 24000;	/* 24.0 MHz */
 			break;
 		case INTEL_FAM6_SKYLAKE_X:
+		case INTEL_FAM6_ATOM_DENVERTON:
 			crystal_khz = 25000;	/* 25.0 MHz */
 			break;
 		case INTEL_FAM6_ATOM_GOLDMONT: