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x86/tsc_msr: Update comments, expand definitions

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Syntax only, no functional change.

Signed-off-by: Len Brown <len.brown@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/8653a2dba21fef122fc7b29eafb750e2004d3976.1466138954.git.len.brown@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Len Brown 2016-06-17 01:22:46 -04:00 committed by Ingo Molnar
parent 14bb4e3486
commit 9e0cae9f62
1 changed files with 10 additions and 26 deletions
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36
arch/x86/kernel/tsc_msr.c
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@ -1,14 +1,5 @@
/* /*
* tsc_msr.c - MSR based TSC calibration on Intel Atom SoC platforms. * tsc_msr.c - TSC frequency enumeration via MSR
*
* TSC in Intel Atom SoC runs at a constant rate which can be figured
* by this formula:
* <maximum core-clock to bus-clock ratio> * <maximum resolved frequency>
* See Intel 64 and IA-32 System Programming Guid section 16.12 and 30.11.5
* for details.
* Especially some Intel Atom SoCs don't have PIT(i8254) or HPET, so MSR
* based calibration is the only option.
*
* *
* Copyright (C) 2013 Intel Corporation * Copyright (C) 2013 Intel Corporation
* Author: Bin Gao <bin.gao@intel.com> * Author: Bin Gao <bin.gao@intel.com>
@ -22,17 +13,10 @@
#include <asm/apic.h> #include <asm/apic.h>
#include <asm/param.h> #include <asm/param.h>
/* CPU reference clock frequency: in KHz */
#define FREQ_83 83200
#define FREQ_100 99840
#define FREQ_133 133200
#define FREQ_166 166400
#define MAX_NUM_FREQS 8 #define MAX_NUM_FREQS 8
/* /*
* According to Intel 64 and IA-32 System Programming Guide, * If MSR_PERF_STAT[31] is set, the maximum resolved bus ratio can be
* if MSR_PERF_STAT[31] is set, the maximum resolved bus ratio can be
* read in MSR_PLATFORM_ID[12:8], otherwise in MSR_PERF_STAT[44:40]. * read in MSR_PLATFORM_ID[12:8], otherwise in MSR_PERF_STAT[44:40].
* Unfortunately some Intel Atom SoCs aren't quite compliant to this, * Unfortunately some Intel Atom SoCs aren't quite compliant to this,
* so we need manually differentiate SoC families. This is what the * so we need manually differentiate SoC families. This is what the
@ -47,15 +31,15 @@ struct freq_desc {
static struct freq_desc freq_desc_tables[] = { static struct freq_desc freq_desc_tables[] = {
/* PNW */ /* PNW */
{ 6, 0x27, 0, { 0, 0, 0, 0, 0, FREQ_100, 0, FREQ_83 } }, { 6, 0x27, 0, { 0, 0, 0, 0, 0, 99840, 0, 83200 } },
/* CLV+ */ /* CLV+ */
{ 6, 0x35, 0, { 0, FREQ_133, 0, 0, 0, FREQ_100, 0, FREQ_83 } }, { 6, 0x35, 0, { 0, 133200, 0, 0, 0, 99840, 0, 83200 } },
/* TNG */ /* TNG - Intel Atom processor Z3400 series */
{ 6, 0x4a, 1, { 0, FREQ_100, FREQ_133, 0, 0, 0, 0, 0 } }, { 6, 0x4a, 1, { 0, 99840, 133200, 0, 0, 0, 0, 0 } },
/* VLV2 */ /* VLV2 - Intel Atom processor E3000, Z3600, Z3700 series */
{ 6, 0x37, 1, { FREQ_83, FREQ_100, FREQ_133, FREQ_166, 0, 0, 0, 0 } }, { 6, 0x37, 1, { 83200, 99840, 133200, 166400, 0, 0, 0, 0 } },
/* ANN */ /* ANN - Intel Atom processor Z3500 series */
{ 6, 0x5a, 1, { FREQ_83, FREQ_100, FREQ_133, FREQ_100, 0, 0, 0, 0 } }, { 6, 0x5a, 1, { 83200, 99840, 133200, 99840, 0, 0, 0, 0 } },
}; };
static int match_cpu(u8 family, u8 model) static int match_cpu(u8 family, u8 model)