linux_dsm_epyc7002/arch/x86/kernel/tsc_msr.c

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// SPDX-License-Identifier: GPL-2.0
/*
* TSC frequency enumeration via MSR
*
* Copyright (C) 2013, 2018 Intel Corporation
* Author: Bin Gao <bin.gao@intel.com>
*/
#include <linux/kernel.h>
#include <asm/apic.h>
#include <asm/cpu_device_id.h>
#include <asm/intel-family.h>
#include <asm/msr.h>
#include <asm/param.h>
#include <asm/tsc.h>
#define MAX_NUM_FREQS 16 /* 4 bits to select the frequency */
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
/*
* The frequency numbers in the SDM are e.g. 83.3 MHz, which does not contain a
* lot of accuracy which leads to clock drift. As far as we know Bay Trail SoCs
* use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal
* is the source clk for a root PLL which outputs 1600 and 100 MHz. It is
* unclear if the root PLL outputs are used directly by the CPU clock PLL or
* if there is another PLL in between.
* This does not matter though, we can model the chain of PLLs as a single PLL
* with a quotient equal to the quotients of all PLLs in the chain multiplied.
* So we can create a simplified model of the CPU clock setup using a reference
* clock of 100 MHz plus a quotient which gets us as close to the frequency
* from the SDM as possible.
* For the 83.3 MHz example from above this would give us 100 MHz * 5 / 6 =
* 83 and 1/3 MHz, which matches exactly what has been measured on actual hw.
*/
#define TSC_REFERENCE_KHZ 100000
struct muldiv {
u32 multiplier;
u32 divider;
};
/*
* 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].
* Unfortunately some Intel Atom SoCs aren't quite compliant to this,
* so we need manually differentiate SoC families. This is what the
* field use_msr_plat does.
*/
struct freq_desc {
bool use_msr_plat;
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
struct muldiv muldiv[MAX_NUM_FREQS];
/*
* Some CPU frequencies in the SDM do not map to known PLL freqs, in
* that case the muldiv array is empty and the freqs array is used.
*/
u32 freqs[MAX_NUM_FREQS];
u32 mask;
};
/*
* Penwell and Clovertrail use spread spectrum clock,
* so the freq number is not exactly the same as reported
* by MSR based on SDM.
*/
static const struct freq_desc freq_desc_pnw = {
.use_msr_plat = false,
.freqs = { 0, 0, 0, 0, 0, 99840, 0, 83200 },
.mask = 0x07,
};
static const struct freq_desc freq_desc_clv = {
.use_msr_plat = false,
.freqs = { 0, 133200, 0, 0, 0, 99840, 0, 83200 },
.mask = 0x07,
};
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
/*
* Bay Trail SDM MSR_FSB_FREQ frequencies simplified PLL model:
* 000: 100 * 5 / 6 = 83.3333 MHz
* 001: 100 * 1 / 1 = 100.0000 MHz
* 010: 100 * 4 / 3 = 133.3333 MHz
* 011: 100 * 7 / 6 = 116.6667 MHz
* 100: 100 * 4 / 5 = 80.0000 MHz
*/
static const struct freq_desc freq_desc_byt = {
.use_msr_plat = true,
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
.muldiv = { { 5, 6 }, { 1, 1 }, { 4, 3 }, { 7, 6 },
{ 4, 5 } },
.mask = 0x07,
};
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
/*
* Cherry Trail SDM MSR_FSB_FREQ frequencies simplified PLL model:
* 0000: 100 * 5 / 6 = 83.3333 MHz
* 0001: 100 * 1 / 1 = 100.0000 MHz
* 0010: 100 * 4 / 3 = 133.3333 MHz
* 0011: 100 * 7 / 6 = 116.6667 MHz
* 0100: 100 * 4 / 5 = 80.0000 MHz
* 0101: 100 * 14 / 15 = 93.3333 MHz
* 0110: 100 * 9 / 10 = 90.0000 MHz
* 0111: 100 * 8 / 9 = 88.8889 MHz
* 1000: 100 * 7 / 8 = 87.5000 MHz
*/
static const struct freq_desc freq_desc_cht = {
.use_msr_plat = true,
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
.muldiv = { { 5, 6 }, { 1, 1 }, { 4, 3 }, { 7, 6 },
{ 4, 5 }, { 14, 15 }, { 9, 10 }, { 8, 9 },
{ 7, 8 } },
.mask = 0x0f,
};
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
/*
* Merriefield SDM MSR_FSB_FREQ frequencies simplified PLL model:
* 0001: 100 * 1 / 1 = 100.0000 MHz
* 0010: 100 * 4 / 3 = 133.3333 MHz
*/
static const struct freq_desc freq_desc_tng = {
.use_msr_plat = true,
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
.muldiv = { { 0, 0 }, { 1, 1 }, { 4, 3 } },
.mask = 0x07,
};
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
/*
* Moorefield SDM MSR_FSB_FREQ frequencies simplified PLL model:
* 0000: 100 * 5 / 6 = 83.3333 MHz
* 0001: 100 * 1 / 1 = 100.0000 MHz
* 0010: 100 * 4 / 3 = 133.3333 MHz
* 0011: 100 * 1 / 1 = 100.0000 MHz
*/
static const struct freq_desc freq_desc_ann = {
.use_msr_plat = true,
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
.muldiv = { { 5, 6 }, { 1, 1 }, { 4, 3 }, { 1, 1 } },
.mask = 0x0f,
};
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
/* 24 MHz crystal? : 24 * 13 / 4 = 78 MHz */
static const struct freq_desc freq_desc_lgm = {
.use_msr_plat = true,
.freqs = { 78000, 78000, 78000, 78000, 78000, 78000, 78000, 78000 },
.mask = 0x0f,
};
static const struct x86_cpu_id tsc_msr_cpu_ids[] = {
X86_MATCH_INTEL_FAM6_MODEL(ATOM_SALTWELL_MID, &freq_desc_pnw),
X86_MATCH_INTEL_FAM6_MODEL(ATOM_SALTWELL_TABLET,&freq_desc_clv),
X86_MATCH_INTEL_FAM6_MODEL(ATOM_SILVERMONT, &freq_desc_byt),
X86_MATCH_INTEL_FAM6_MODEL(ATOM_SILVERMONT_MID, &freq_desc_tng),
X86_MATCH_INTEL_FAM6_MODEL(ATOM_AIRMONT, &freq_desc_cht),
X86_MATCH_INTEL_FAM6_MODEL(ATOM_AIRMONT_MID, &freq_desc_ann),
X86_MATCH_INTEL_FAM6_MODEL(ATOM_AIRMONT_NP, &freq_desc_lgm),
{}
};
/*
* MSR-based CPU/TSC frequency discovery for certain CPUs.
x86, tsc: Fallback to normal calibration if fast MSR calibration fails If we cannot calibrate TSC via MSR based calibration try_msr_calibrate_tsc() stores zero to fast_calibrate and returns that to the caller. This value gets then propagated further to clockevents code resulting division by zero oops like the one below: divide error: 0000 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 3.13.0+ #47 task: ffff880075508000 ti: ffff880075506000 task.ti: ffff880075506000 RIP: 0010:[<ffffffff810aec14>] [<ffffffff810aec14>] clockevents_config.part.3+0x24/0xa0 RSP: 0000:ffff880075507e58 EFLAGS: 00010246 RAX: ffffffffffffffff RBX: ffff880079c0cd80 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffffffffff RBP: ffff880075507e70 R08: 0000000000000001 R09: 00000000000000be R10: 00000000000000bd R11: 0000000000000003 R12: 000000000000b008 R13: 0000000000000008 R14: 000000000000b010 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff880079c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: ffff880079fff000 CR3: 0000000001c0b000 CR4: 00000000001006f0 Stack: ffff880079c0cd80 000000000000b008 0000000000000008 ffff880075507e88 ffffffff810aecb0 ffff880079c0cd80 ffff880075507e98 ffffffff81030168 ffff880075507ed8 ffffffff81d1104f 00000000000000c3 0000000000000000 Call Trace: [<ffffffff810aecb0>] clockevents_config_and_register+0x20/0x30 [<ffffffff81030168>] setup_APIC_timer+0xc8/0xd0 [<ffffffff81d1104f>] setup_boot_APIC_clock+0x4cc/0x4d8 [<ffffffff81d0f5de>] native_smp_prepare_cpus+0x3dd/0x3f0 [<ffffffff81d02ee9>] kernel_init_freeable+0xc3/0x205 [<ffffffff8177c910>] ? rest_init+0x90/0x90 [<ffffffff8177c91e>] kernel_init+0xe/0x120 [<ffffffff8178deec>] ret_from_fork+0x7c/0xb0 [<ffffffff8177c910>] ? rest_init+0x90/0x90 Prevent this from happening by: 1) Modifying try_msr_calibrate_tsc() to return calibration value or zero if it fails. 2) Check this return value in native_calibrate_tsc() and in case of zero fallback to use normal non-MSR based calibration. [mw: Added subject and changelog] Reported-and-tested-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Bin Gao <bin.gao@linux.intel.com> Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> Cc: Ingo Molnar <mingo@kernel.org> Cc: H. Peter Anvin <hpa@zytor.com> Link: http://lkml.kernel.org/r/1392810750-18660-1-git-send-email-mika.westerberg@linux.intel.com Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-02-19 18:52:29 +07:00
*
* Set global "lapic_timer_period" to bus_clock_cycles/jiffy
* Return processor base frequency in KHz, or 0 on failure.
*/
unsigned long cpu_khz_from_msr(void)
{
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
u32 lo, hi, ratio, freq, tscref;
const struct freq_desc *freq_desc;
const struct x86_cpu_id *id;
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
const struct muldiv *md;
x86, tsc: Fallback to normal calibration if fast MSR calibration fails If we cannot calibrate TSC via MSR based calibration try_msr_calibrate_tsc() stores zero to fast_calibrate and returns that to the caller. This value gets then propagated further to clockevents code resulting division by zero oops like the one below: divide error: 0000 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 3.13.0+ #47 task: ffff880075508000 ti: ffff880075506000 task.ti: ffff880075506000 RIP: 0010:[<ffffffff810aec14>] [<ffffffff810aec14>] clockevents_config.part.3+0x24/0xa0 RSP: 0000:ffff880075507e58 EFLAGS: 00010246 RAX: ffffffffffffffff RBX: ffff880079c0cd80 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffffffffff RBP: ffff880075507e70 R08: 0000000000000001 R09: 00000000000000be R10: 00000000000000bd R11: 0000000000000003 R12: 000000000000b008 R13: 0000000000000008 R14: 000000000000b010 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff880079c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: ffff880079fff000 CR3: 0000000001c0b000 CR4: 00000000001006f0 Stack: ffff880079c0cd80 000000000000b008 0000000000000008 ffff880075507e88 ffffffff810aecb0 ffff880079c0cd80 ffff880075507e98 ffffffff81030168 ffff880075507ed8 ffffffff81d1104f 00000000000000c3 0000000000000000 Call Trace: [<ffffffff810aecb0>] clockevents_config_and_register+0x20/0x30 [<ffffffff81030168>] setup_APIC_timer+0xc8/0xd0 [<ffffffff81d1104f>] setup_boot_APIC_clock+0x4cc/0x4d8 [<ffffffff81d0f5de>] native_smp_prepare_cpus+0x3dd/0x3f0 [<ffffffff81d02ee9>] kernel_init_freeable+0xc3/0x205 [<ffffffff8177c910>] ? rest_init+0x90/0x90 [<ffffffff8177c91e>] kernel_init+0xe/0x120 [<ffffffff8178deec>] ret_from_fork+0x7c/0xb0 [<ffffffff8177c910>] ? rest_init+0x90/0x90 Prevent this from happening by: 1) Modifying try_msr_calibrate_tsc() to return calibration value or zero if it fails. 2) Check this return value in native_calibrate_tsc() and in case of zero fallback to use normal non-MSR based calibration. [mw: Added subject and changelog] Reported-and-tested-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Bin Gao <bin.gao@linux.intel.com> Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> Cc: Ingo Molnar <mingo@kernel.org> Cc: H. Peter Anvin <hpa@zytor.com> Link: http://lkml.kernel.org/r/1392810750-18660-1-git-send-email-mika.westerberg@linux.intel.com Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-02-19 18:52:29 +07:00
unsigned long res;
int index;
id = x86_match_cpu(tsc_msr_cpu_ids);
if (!id)
return 0;
freq_desc = (struct freq_desc *)id->driver_data;
if (freq_desc->use_msr_plat) {
rdmsr(MSR_PLATFORM_INFO, lo, hi);
ratio = (lo >> 8) & 0xff;
} else {
rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
ratio = (hi >> 8) & 0x1f;
}
/* Get FSB FREQ ID */
rdmsr(MSR_FSB_FREQ, lo, hi);
index = lo & freq_desc->mask;
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
md = &freq_desc->muldiv[index];
x86/tsc_msr: Make MSR derived TSC frequency more accurate The "Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers" has the following table for the values from freq_desc_byt: 000B: 083.3 MHz 001B: 100.0 MHz 010B: 133.3 MHz 011B: 116.7 MHz 100B: 080.0 MHz Notice how for e.g the 83.3 MHz value there are 3 significant digits, which translates to an accuracy of a 1000 ppm, where as a typical crystal oscillator is 20 - 100 ppm, so the accuracy of the frequency format used in the Software Developer’s Manual is not really helpful. As far as we know Bay Trail SoCs use a 25 MHz crystal and Cherry Trail uses a 19.2 MHz crystal, the crystal is the source clock for a root PLL which outputs 1600 and 100 MHz. It is unclear if the root PLL outputs are used directly by the CPU clock PLL or if there is another PLL in between. This does not matter though, we can model the chain of PLLs as a single PLL with a quotient equal to the quotients of all PLLs in the chain multiplied. So we can create a simplified model of the CPU clock setup using a reference clock of 100 MHz plus a quotient which gets us as close to the frequency from the SDM as possible. For the 83.3 MHz example from above this would give 100 MHz * 5 / 6 = 83 and 1/3 MHz, which matches exactly what has been measured on actual hardware. Use a simplified PLL model with a reference clock of 100 MHz for all Bay and Cherry Trail models. This has been tested on the following models: CPU freq before: CPU freq after: Intel N2840 2165.800 MHz 2166.667 MHz Intel Z3736 1332.800 MHz 1333.333 MHz Intel Z3775 1466.300 MHz 1466.667 MHz Intel Z8350 1440.000 MHz 1440.000 MHz Intel Z8750 1600.000 MHz 1600.000 MHz This fixes the time drifting by about 1 second per hour (20 - 30 seconds per day) on (some) devices which rely on the tsc_msr.c code to determine the TSC frequency. Reported-by: Vipul Kumar <vipulk0511@gmail.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200223140610.59612-3-hdegoede@redhat.com
2020-02-23 21:06:10 +07:00
/*
* Note this also catches cases where the index points to an unpopulated
* part of muldiv, in that case the else will set freq and res to 0.
*/
if (md->divider) {
tscref = TSC_REFERENCE_KHZ * md->multiplier;
freq = DIV_ROUND_CLOSEST(tscref, md->divider);
/*
* Multiplying by ratio before the division has better
* accuracy than just calculating freq * ratio.
*/
res = DIV_ROUND_CLOSEST(tscref * ratio, md->divider);
} else {
freq = freq_desc->freqs[index];
res = freq * ratio;
}
if (freq == 0)
pr_err("Error MSR_FSB_FREQ index %d is unknown\n", index);
#ifdef CONFIG_X86_LOCAL_APIC
lapic_timer_period = (freq * 1000) / HZ;
#endif
/*
* TSC frequency determined by MSR is always considered "known"
* because it is reported by HW.
* Another fact is that on MSR capable platforms, PIT/HPET is
* generally not available so calibration won't work at all.
*/
setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
/*
* Unfortunately there is no way for hardware to tell whether the
* TSC is reliable. We were told by silicon design team that TSC
* on Atom SoCs are always "reliable". TSC is also the only
* reliable clocksource on these SoCs (HPET is either not present
* or not functional) so mark TSC reliable which removes the
* requirement for a watchdog clocksource.
*/
setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
x86, tsc: Fallback to normal calibration if fast MSR calibration fails If we cannot calibrate TSC via MSR based calibration try_msr_calibrate_tsc() stores zero to fast_calibrate and returns that to the caller. This value gets then propagated further to clockevents code resulting division by zero oops like the one below: divide error: 0000 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 3.13.0+ #47 task: ffff880075508000 ti: ffff880075506000 task.ti: ffff880075506000 RIP: 0010:[<ffffffff810aec14>] [<ffffffff810aec14>] clockevents_config.part.3+0x24/0xa0 RSP: 0000:ffff880075507e58 EFLAGS: 00010246 RAX: ffffffffffffffff RBX: ffff880079c0cd80 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffffffffff RBP: ffff880075507e70 R08: 0000000000000001 R09: 00000000000000be R10: 00000000000000bd R11: 0000000000000003 R12: 000000000000b008 R13: 0000000000000008 R14: 000000000000b010 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff880079c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: ffff880079fff000 CR3: 0000000001c0b000 CR4: 00000000001006f0 Stack: ffff880079c0cd80 000000000000b008 0000000000000008 ffff880075507e88 ffffffff810aecb0 ffff880079c0cd80 ffff880075507e98 ffffffff81030168 ffff880075507ed8 ffffffff81d1104f 00000000000000c3 0000000000000000 Call Trace: [<ffffffff810aecb0>] clockevents_config_and_register+0x20/0x30 [<ffffffff81030168>] setup_APIC_timer+0xc8/0xd0 [<ffffffff81d1104f>] setup_boot_APIC_clock+0x4cc/0x4d8 [<ffffffff81d0f5de>] native_smp_prepare_cpus+0x3dd/0x3f0 [<ffffffff81d02ee9>] kernel_init_freeable+0xc3/0x205 [<ffffffff8177c910>] ? rest_init+0x90/0x90 [<ffffffff8177c91e>] kernel_init+0xe/0x120 [<ffffffff8178deec>] ret_from_fork+0x7c/0xb0 [<ffffffff8177c910>] ? rest_init+0x90/0x90 Prevent this from happening by: 1) Modifying try_msr_calibrate_tsc() to return calibration value or zero if it fails. 2) Check this return value in native_calibrate_tsc() and in case of zero fallback to use normal non-MSR based calibration. [mw: Added subject and changelog] Reported-and-tested-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Bin Gao <bin.gao@linux.intel.com> Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> Cc: Ingo Molnar <mingo@kernel.org> Cc: H. Peter Anvin <hpa@zytor.com> Link: http://lkml.kernel.org/r/1392810750-18660-1-git-send-email-mika.westerberg@linux.intel.com Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-02-19 18:52:29 +07:00
return res;
}