tools/power/cpupower/debug/kernel/cpufreq-test_tsc.c

   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  *     linux-pm@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 #include <linux/acpi.h>
  29 #include <asm/io.h>
  30
  31 static int pm_tmr_ioport = 0;
  32
  33 /*helper function to safely read acpi pm timesource*/
  34 static u32 read_pmtmr(void)
  35 {
  36         u32 v1=0,v2=0,v3=0;
  37         /* It has been reported that because of various broken
  38          * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM time
  39          * source is not latched, so you must read it multiple
  40          * times to insure a safe value is read.
  41          */
  42         do {
  43                 v1 = inl(pm_tmr_ioport);
  44                 v2 = inl(pm_tmr_ioport);
  45                 v3 = inl(pm_tmr_ioport);
  46         } while ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
  47                  || (v3 > v1 && v3 < v2));
  48
  49         /* mask the output to 24 bits */
  50         return (v2 & 0xFFFFFF);
  51 }
  52
  53 static int __init cpufreq_test_tsc(void)
  54 {
  55         u32 now, then, diff;
  56         u64 now_tsc, then_tsc, diff_tsc;
  57         int i;
  58
  59         /* the following code snipped is copied from arch/x86/kernel/acpi/boot.c
  60            of Linux v2.6.25. */
  61
  62         /* detect the location of the ACPI PM Timer */
  63         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID) {
  64                 /* FADT rev. 2 */
  65                 if (acpi_gbl_FADT.xpm_timer_block.space_id !=
  66                     ACPI_ADR_SPACE_SYSTEM_IO)
  67                         return 0;
  68
  69                 pm_tmr_ioport = acpi_gbl_FADT.xpm_timer_block.address;
  70                 /*
  71                  * "X" fields are optional extensions to the original V1.0
  72                  * fields, so we must selectively expand V1.0 fields if the
  73                  * corresponding X field is zero.
  74                  */
  75                 if (!pm_tmr_ioport)
  76                         pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
  77         } else {
  78                 /* FADT rev. 1 */
  79                 pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
  80         }
  81
  82         printk(KERN_DEBUG "start--> \n");
  83         then = read_pmtmr();
  84         then_tsc = rdtsc();
  85         for (i=0;i<20;i++) {
  86                 mdelay(100);
  87                 now = read_pmtmr();
  88                 now_tsc = rdtsc();
  89                 diff = (now - then) & 0xFFFFFF;
  90                 diff_tsc = now_tsc - then_tsc;
  91                 printk(KERN_DEBUG "t1: %08u t2: %08u diff_pmtmr: %08u diff_tsc: %016llu\n", then, now, diff, diff_tsc);
  92                 then = now;
  93                 then_tsc = now_tsc;
  94         }
  95         printk(KERN_DEBUG "<-- end \n");
  96         return -ENODEV;
  97 }
  98
  99 static void __exit cpufreq_none(void)
 100 {
 101         return;
 102 }
 103
 104 module_init(cpufreq_test_tsc)
 105 module_exit(cpufreq_none)
 106
 107
 108 MODULE_AUTHOR("Dominik Brodowski");
 109 MODULE_DESCRIPTION("Verify the TSC cpufreq notifier working correctly -- needs ACPI-enabled system");
 110 MODULE_LICENSE ("GPL");