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

   1/*
   2 * test module to check whether the TSC-based delay routine continues
   3 * to work properly after cpufreq transitions. Needs ACPI to work
   4 * properly.
   5 *
   6 * Based partly on the Power Management Timer (PMTMR) code to be found
   7 * in arch/i386/kernel/timers/timer_pm.c on recent 2.6. kernels, especially
   8 * code written by John Stultz. The read_pmtmr function was copied verbatim
   9 * from that file.
  10 *
  11 * (C) 2004 Dominik Brodowski
  12 *
  13 * To use:
  14 * 1.) pass clock=tsc to the kernel on your bootloader
  15 * 2.) modprobe this module (it'll fail)
  16 * 3.) change CPU frequency
  17 * 4.) modprobe this module again
  18 * 5.) if the third value, "diff_pmtmr", changes between 2. and 4., the
  19 *     TSC-based delay routine on the Linux kernel does not correctly
  20 *     handle the cpufreq transition. Please report this to
  21 *     cpufreq@vger.kernel.org
  22 */
  23
  24#include <linux/kernel.h>
  25#include <linux/module.h>
  26#include <linux/init.h>
  27#include <linux/delay.h>
  28
  29#include <asm/io.h>
  30
  31#include <acpi/acpi_bus.h>
  32#include <acpi/acpi_drivers.h>
  33
  34static int pm_tmr_ioport = 0;
  35
  36/*helper function to safely read acpi pm timesource*/
  37static u32 read_pmtmr(void)
  38{
  39        u32 v1=0,v2=0,v3=0;
  40        /* It has been reported that because of various broken
  41         * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM time
  42         * source is not latched, so you must read it multiple
  43         * times to insure a safe value is read.
  44         */
  45        do {
  46                v1 = inl(pm_tmr_ioport);
  47                v2 = inl(pm_tmr_ioport);
  48                v3 = inl(pm_tmr_ioport);
  49        } while ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
  50                 || (v3 > v1 && v3 < v2));
  51
  52        /* mask the output to 24 bits */
  53        return (v2 & 0xFFFFFF);
  54}
  55
  56static int __init cpufreq_test_tsc(void)
  57{
  58        u32 now, then, diff;
  59        u64 now_tsc, then_tsc, diff_tsc;
  60        int i;
  61
  62        /* the following code snipped is copied from arch/x86/kernel/acpi/boot.c
  63           of Linux v2.6.25. */
  64
  65        /* detect the location of the ACPI PM Timer */
  66        if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID) {
  67                /* FADT rev. 2 */
  68                if (acpi_gbl_FADT.xpm_timer_block.space_id !=
  69                    ACPI_ADR_SPACE_SYSTEM_IO)
  70                        return 0;
  71
  72                pm_tmr_ioport = acpi_gbl_FADT.xpm_timer_block.address;
  73                /*
  74                 * "X" fields are optional extensions to the original V1.0
  75                 * fields, so we must selectively expand V1.0 fields if the
  76                 * corresponding X field is zero.
  77                 */
  78                if (!pm_tmr_ioport)
  79                        pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
  80        } else {
  81                /* FADT rev. 1 */
  82                pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
  83        }
  84
  85        printk(KERN_DEBUG "start--> \n");
  86        then = read_pmtmr();
  87        rdtscll(then_tsc);
  88        for (i=0;i<20;i++) {
  89                mdelay(100);
  90                now = read_pmtmr();
  91                rdtscll(now_tsc);
  92                diff = (now - then) & 0xFFFFFF;
  93                diff_tsc = now_tsc - then_tsc;
  94                printk(KERN_DEBUG "t1: %08u t2: %08u diff_pmtmr: %08u diff_tsc: %016llu\n", then, now, diff, diff_tsc);
  95                then = now;
  96                then_tsc = now_tsc;
  97        }
  98        printk(KERN_DEBUG "<-- end \n");
  99        return -ENODEV;
 100}
 101
 102static void __exit cpufreq_none(void)
 103{
 104        return;
 105}
 106
 107module_init(cpufreq_test_tsc)
 108module_exit(cpufreq_none)
 109
 110
 111MODULE_AUTHOR("Dominik Brodowski");
 112MODULE_DESCRIPTION("Verify the TSC cpufreq notifier working correctly -- needs ACPI-enabled system");
 113MODULE_LICENSE ("GPL");
 114