* [PATCH] x86 tsc: Add the Intel Denverton Processor to native_calibrate_tsc()
@ 2017-01-13 6:11 Len Brown
2017-01-14 9:58 ` [tip:x86/urgent] x86/tsc: " tip-bot for Len Brown
0 siblings, 1 reply; 2+ messages in thread
From: Len Brown @ 2017-01-13 6:11 UTC (permalink / raw)
To: x86; +Cc: linux-kernel, Len Brown
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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [tip:x86/urgent] x86/tsc: Add the Intel Denverton Processor to native_calibrate_tsc()
2017-01-13 6:11 [PATCH] x86 tsc: Add the Intel Denverton Processor to native_calibrate_tsc() Len Brown
@ 2017-01-14 9:58 ` tip-bot for Len Brown
0 siblings, 0 replies; 2+ messages in thread
From: tip-bot for Len Brown @ 2017-01-14 9:58 UTC (permalink / raw)
To: linux-tip-commits
Cc: torvalds, len.brown, hpa, peterz, tglx, mingo, linux-kernel
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:
^ permalink raw reply related [flat|nested] 2+ messages in thread
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