text: /*
   * 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
   *     cpufreq@vger.kernel.org
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/delay.h>
  
  #include <asm/io.h>
  
  #include <acpi/acpi_bus.h>
  #include <acpi/acpi_drivers.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");
  