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[PATCH for v4.9 LTS 70/86] x86/tsc: Add the Intel Denverton Processor to native_calibrate_tsc()




From: Len Brown <len.brown@xxxxxxxxx>

[ Upstream commit 695085b4bc7603551db0b3da897b8bf9893ca218 ]

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@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/306899f94804aece6d8fa8b4223ede3b48dbb59c.1484287748.git.len.brown@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
 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 eea88fe5d969..6e57edf33d75 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