LXR linux/tools/power/cpupower/debug/kernel/cpufreq-test

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * test module to check whether the TSC-based delay routine continues
   4 * to work properly after cpufreq transitions. Needs ACPI to work
   5 * properly.
   6 *
   7 * Based partly on the Power Management Timer (PMTMR) code to be found
   8 * in arch/i386/kernel/timers/timer_pm.c on recent 2.6. kernels, especially
   9 * code written by John Stultz. The read_pmtmr function was copied verbatim
  10 * from that file.
  11 *
  12 * (C) 2004 Dominik Brodowski
  13 *
  14 * To use:
  15 * 1.) pass clock=tsc to the kernel on your bootloader
  16 * 2.) modprobe this module (it'll fail)
  17 * 3.) change CPU frequency
  18 * 4.) modprobe this module again
  19 * 5.) if the third value, "diff_pmtmr", changes between 2. and 4., the
  20 *     TSC-based delay routine on the Linux kernel does not correctly
  21 *     handle the cpufreq transition. Please report this to
  22 *     linux-pm@vger.kernel.org
  23 */
  24
  25#include <linux/kernel.h>
  26#include <linux/module.h>
  27#include <linux/init.h>
  28#include <linux/delay.h>
  29#include <linux/acpi.h>
  30#include <asm/io.h>
  31
  32static int pm_tmr_ioport = 0;
  33
  34/*helper function to safely read acpi pm timesource*/
  35static u32 read_pmtmr(void)
  36{
  37        u32 v1=0,v2=0,v3=0;
  38        /* It has been reported that because of various broken
  39         * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM time
  40         * source is not latched, so you must read it multiple
  41         * times to insure a safe value is read.
  42         */
  43        do {
  44                v1 = inl(pm_tmr_ioport);
  45                v2 = inl(pm_tmr_ioport);
  46                v3 = inl(pm_tmr_ioport);
  47        } while ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
  48                 || (v3 > v1 && v3 < v2));
  49
  50        /* mask the output to 24 bits */
  51        return (v2 & 0xFFFFFF);
  52}
  53
  54static int __init cpufreq_test_tsc(void)
  55{
  56        u32 now, then, diff;
  57        u64 now_tsc, then_tsc, diff_tsc;
  58        int i;
  59
  60        /* the following code snipped is copied from arch/x86/kernel/acpi/boot.c
  61           of Linux v2.6.25. */
  62
  63        /* detect the location of the ACPI PM Timer */
  64        if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID) {
  65                /* FADT rev. 2 */
  66                if (acpi_gbl_FADT.xpm_timer_block.space_id !=
  67                    ACPI_ADR_SPACE_SYSTEM_IO)
  68                        return 0;
  69
  70                pm_tmr_ioport = acpi_gbl_FADT.xpm_timer_block.address;
  71                /*
  72                 * "X" fields are optional extensions to the original V1.0
  73                 * fields, so we must selectively expand V1.0 fields if the
  74                 * corresponding X field is zero.
  75                 */
  76                if (!pm_tmr_ioport)
  77                        pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
  78        } else {
  79                /* FADT rev. 1 */
  80                pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
  81        }
  82
  83        printk(KERN_DEBUG "start--> \n");
  84        then = read_pmtmr();
  85        then_tsc = rdtsc();
  86        for (i=0;i<20;i++) {
  87                mdelay(100);
  88                now = read_pmtmr();
  89                now_tsc = rdtsc();
  90                diff = (now - then) & 0xFFFFFF;
  91                diff_tsc = now_tsc - then_tsc;
  92                printk(KERN_DEBUG "t1: %08u t2: %08u diff_pmtmr: %08u diff_tsc: %016llu\n", then, now, diff, diff_tsc);
  93                then = now;
  94                then_tsc = now_tsc;
  95        }
  96        printk(KERN_DEBUG "<-- end \n");
  97        return -ENODEV;
  98}
  99
 100static void __exit cpufreq_none(void)
 101{
 102        return;
 103}
 104
 105module_init(cpufreq_test_tsc)
 106module_exit(cpufreq_none)
 107
 108
 109MODULE_AUTHOR("Dominik Brodowski");
 110MODULE_DESCRIPTION("Verify the TSC cpufreq notifier working correctly -- needs ACPI-enabled system");
 111MODULE_LICENSE ("GPL");
 112