2 * test module to check whether the TSC-based delay routine continues
3 * to work properly after cpufreq transitions. Needs ACPI to work
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
11 * (C) 2004 Dominik Brodowski
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
24 #include <linux/kernel.h>
25 #include <linux/module.h>
26 #include <linux/init.h>
27 #include <linux/delay.h>
31 #include <acpi/acpi_bus.h>
32 #include <acpi/acpi_drivers.h>
34 static int pm_tmr_ioport = 0;
36 /*helper function to safely read acpi pm timesource*/
37 static u32 read_pmtmr(void)
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.
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));
52 /* mask the output to 24 bits */
53 return (v2 & 0xFFFFFF);
56 static int __init cpufreq_test_tsc(void)
59 u64 now_tsc, then_tsc, diff_tsc;
62 /* the following code snipped is copied from arch/x86/kernel/acpi/boot.c
65 /* detect the location of the ACPI PM Timer */
66 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID) {
68 if (acpi_gbl_FADT.xpm_timer_block.space_id !=
69 ACPI_ADR_SPACE_SYSTEM_IO)
72 pm_tmr_ioport = acpi_gbl_FADT.xpm_timer_block.address;
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.
79 pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
82 pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
85 printk(KERN_DEBUG "start--> \n");
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);
98 printk(KERN_DEBUG "<-- end \n");
102 static void __exit cpufreq_none(void)
107 module_init(cpufreq_test_tsc)
108 module_exit(cpufreq_none)
111 MODULE_AUTHOR("Dominik Brodowski");
112 MODULE_DESCRIPTION("Verify the TSC cpufreq notifier working correctly -- needs ACPI-enabled system");
113 MODULE_LICENSE ("GPL");