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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
31static int pm_tmr_ioport = 0;
32
33/*helper function to safely read acpi pm timesource*/
34static 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
53static 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
99static void __exit cpufreq_none(void)
100{
101 return;
102}
103
104module_init(cpufreq_test_tsc)
105module_exit(cpufreq_none)
106
107
108MODULE_AUTHOR("Dominik Brodowski");
109MODULE_DESCRIPTION("Verify the TSC cpufreq notifier working correctly -- needs ACPI-enabled system");
110MODULE_LICENSE ("GPL");
111

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