From: Len Brown <lenb@kernel.org>
To: x86@kernel.org
Cc: linux-kernel@vger.kernel.org, Len Brown <len.brown@intel.com>
Subject: [PATCH] x86 tsc: Add the Intel Denverton Processor to native_calibrate_tsc()
Date: Fri, 13 Jan 2017 01:11:18 -0500
Message-ID: <306899f94804aece6d8fa8b4223ede3b48dbb59c.1484287748.git.len.brown@intel.com> (raw)
From: Len Brown <len.brown@intel.com>
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>
---
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 46b2f41f8b05..b3e397a0f29d 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:
--
2.11.0.161.g6610af872
next reply index
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-13 6:11 Len Brown [this message]
2017-01-14 9:58 ` [tip:x86/urgent] x86/tsc: " tip-bot for Len Brown
2017-01-21 7:52 [PATCH] x86 tsc: " Len Brown
2017-01-22 9:33 ` Ingo Molnar
2017-01-23 18:49 ` Len Brown
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