/* * test module to check whether the TSC-based delay routine continues * to work properly after cpufreq transitions. Needs ACPI to work * properly. * * Based partly on the Power Management Timer (PMTMR) code to be found * in arch/i386/kernel/timers/timer_pm.c on recent 2.6. kernels, especially * code written by John Stultz. The read_pmtmr function was copied verbatim * from that file. * * (C) 2004 Dominik Brodowski * * To use: * 1.) pass clock=tsc to the kernel on your bootloader * 2.) modprobe this module (it'll fail) * 3.) change CPU frequency * 4.) modprobe this module again * 5.) if the third value, "diff_pmtmr", changes between 2. and 4., the * TSC-based delay routine on the Linux kernel does not correctly * handle the cpufreq transition. Please report this to * linux-pm@vger.kernel.org */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/init.h> #include <linux/delay.h> #include <linux/acpi.h> #include <asm/io.h> static int pm_tmr_ioport = 0; /*helper function to safely read acpi pm timesource*/ static u32 read_pmtmr(void) { u32 v1=0,v2=0,v3=0; /* It has been reported that because of various broken * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM time * source is not latched, so you must read it multiple * times to insure a safe value is read. */ do { v1 = inl(pm_tmr_ioport); v2 = inl(pm_tmr_ioport); v3 = inl(pm_tmr_ioport); } while ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1) || (v3 > v1 && v3 < v2)); /* mask the output to 24 bits */ return (v2 & 0xFFFFFF); } static int __init cpufreq_test_tsc(void) { u32 now, then, diff; u64 now_tsc, then_tsc, diff_tsc; int i; /* the following code snipped is copied from arch/x86/kernel/acpi/boot.c of Linux v2.6.25. */ /* detect the location of the ACPI PM Timer */ if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID) { /* FADT rev. 2 */ if (acpi_gbl_FADT.xpm_timer_block.space_id != ACPI_ADR_SPACE_SYSTEM_IO) return 0; pm_tmr_ioport = acpi_gbl_FADT.xpm_timer_block.address; /* * "X" fields are optional extensions to the original V1.0 * fields, so we must selectively expand V1.0 fields if the * corresponding X field is zero. */ if (!pm_tmr_ioport) pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block; } else { /* FADT rev. 1 */ pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block; } printk(KERN_DEBUG "start--> \n"); then = read_pmtmr(); rdtscll(then_tsc); for (i=0;i<20;i++) { mdelay(100); now = read_pmtmr(); rdtscll(now_tsc); diff = (now - then) & 0xFFFFFF; diff_tsc = now_tsc - then_tsc; printk(KERN_DEBUG "t1: %08u t2: %08u diff_pmtmr: %08u diff_tsc: %016llu\n", then, now, diff, diff_tsc); then = now; then_tsc = now_tsc; } printk(KERN_DEBUG "<-- end \n"); return -ENODEV; } static void __exit cpufreq_none(void) { return; } module_init(cpufreq_test_tsc) module_exit(cpufreq_none) MODULE_AUTHOR("Dominik Brodowski"); MODULE_DESCRIPTION("Verify the TSC cpufreq notifier working correctly -- needs ACPI-enabled system"); MODULE_LICENSE ("GPL");