From: tip-bot for Len Brown <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: torvalds@linux-foundation.org, len.brown@intel.com,
hpa@zytor.com, peterz@infradead.org, tglx@linutronix.de,
mingo@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip:x86/urgent] x86/tsc: Add the Intel Denverton Processor to native_calibrate_tsc()
Date: Sat, 14 Jan 2017 01:58:35 -0800 [thread overview]
Message-ID: <tip-695085b4bc7603551db0b3da897b8bf9893ca218@git.kernel.org> (raw)
In-Reply-To: <306899f94804aece6d8fa8b4223ede3b48dbb59c.1484287748.git.len.brown@intel.com>
Commit-ID: 695085b4bc7603551db0b3da897b8bf9893ca218
Gitweb: http://git.kernel.org/tip/695085b4bc7603551db0b3da897b8bf9893ca218
Author: Len Brown <len.brown@intel.com>
AuthorDate: Fri, 13 Jan 2017 01:11:18 -0500
Committer: Ingo Molnar <mingo@kernel.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@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/306899f94804aece6d8fa8b4223ede3b48dbb59c.1484287748.git.len.brown@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.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:
prev parent reply other threads:[~2017-01-14 9:59 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-13 6:11 [PATCH] x86 tsc: " Len Brown
2017-01-14 9:58 ` tip-bot for Len Brown [this message]
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