Logo Search packages:      
Sourcecode: linux version File versions  Download package

acpi_pm.c

/*
 * linux/drivers/clocksource/acpi_pm.c
 *
 * This file contains the ACPI PM based clocksource.
 *
 * This code was largely moved from the i386 timer_pm.c file
 * which was (C) Dominik Brodowski <linux@brodo.de> 2003
 * and contained the following comments:
 *
 * Driver to use the Power Management Timer (PMTMR) available in some
 * southbridges as primary timing source for the Linux kernel.
 *
 * Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c,
 * timer_hpet.c, and on Arjan van de Ven's implementation for 2.4.
 *
 * This file is licensed under the GPL v2.
 */

#include <linux/acpi_pmtmr.h>
#include <linux/clocksource.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <asm/io.h>

/*
 * The I/O port the PMTMR resides at.
 * The location is detected during setup_arch(),
 * in arch/i386/kernel/acpi/boot.c
 */
u32 pmtmr_ioport __read_mostly;

static inline u32 read_pmtmr(void)
{
      /* mask the output to 24 bits */
      return inl(pmtmr_ioport) & ACPI_PM_MASK;
}

u32 acpi_pm_read_verified(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 clock
       * source is not latched, you must read it multiple
       * times to ensure a safe value is read:
       */
      do {
            v1 = read_pmtmr();
            v2 = read_pmtmr();
            v3 = read_pmtmr();
      } while (unlikely((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
                    || (v3 > v1 && v3 < v2)));

      return v2;
}

static cycle_t acpi_pm_read_slow(void)
{
      return (cycle_t)acpi_pm_read_verified();
}

static cycle_t acpi_pm_read(void)
{
      return (cycle_t)read_pmtmr();
}

static struct clocksource clocksource_acpi_pm = {
      .name       = "acpi_pm",
      .rating           = 200,
      .read       = acpi_pm_read,
      .mask       = (cycle_t)ACPI_PM_MASK,
      .mult       = 0, /*to be calculated*/
      .shift            = 22,
      .flags            = CLOCK_SOURCE_IS_CONTINUOUS,

};


#ifdef CONFIG_PCI
static int __devinitdata acpi_pm_good;
static int __init acpi_pm_good_setup(char *__str)
{
      acpi_pm_good = 1;
      return 1;
}
__setup("acpi_pm_good", acpi_pm_good_setup);

static inline void acpi_pm_need_workaround(void)
{
      clocksource_acpi_pm.read = acpi_pm_read_slow;
      clocksource_acpi_pm.rating = 120;
}

/*
 * PIIX4 Errata:
 *
 * The power management timer may return improper results when read.
 * Although the timer value settles properly after incrementing,
 * while incrementing there is a 3 ns window every 69.8 ns where the
 * timer value is indeterminate (a 4.2% chance that the data will be
 * incorrect when read). As a result, the ACPI free running count up
 * timer specification is violated due to erroneous reads.
 */
static void __devinit acpi_pm_check_blacklist(struct pci_dev *dev)
{
      if (acpi_pm_good)
            return;

      /* the bug has been fixed in PIIX4M */
      if (dev->revision < 3) {
            printk(KERN_WARNING "* Found PM-Timer Bug on the chipset."
                   " Due to workarounds for a bug,\n"
                   "* this clock source is slow. Consider trying"
                   " other clock sources\n");

            acpi_pm_need_workaround();
      }
}
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3,
                  acpi_pm_check_blacklist);

static void __devinit acpi_pm_check_graylist(struct pci_dev *dev)
{
      if (acpi_pm_good)
            return;

      printk(KERN_WARNING "* The chipset may have PM-Timer Bug. Due to"
             " workarounds for a bug,\n"
             "* this clock source is slow. If you are sure your timer"
             " does not have\n"
             "* this bug, please use \"acpi_pm_good\" to disable the"
             " workaround\n");

      acpi_pm_need_workaround();
}
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82801DB_0,
                  acpi_pm_check_graylist);
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_LE,
                  acpi_pm_check_graylist);
#endif

#ifndef CONFIG_X86_64
#include "mach_timer.h"
#define PMTMR_EXPECTED_RATE \
  ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))
/*
 * Some boards have the PMTMR running way too fast. We check
 * the PMTMR rate against PIT channel 2 to catch these cases.
 */
static int verify_pmtmr_rate(void)
{
      u32 value1, value2;
      unsigned long count, delta;

      mach_prepare_counter();
      value1 = read_pmtmr();
      mach_countup(&count);
      value2 = read_pmtmr();
      delta = (value2 - value1) & ACPI_PM_MASK;

      /* Check that the PMTMR delta is within 5% of what we expect */
      if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 ||
          delta > (PMTMR_EXPECTED_RATE * 21) / 20) {
            printk(KERN_INFO "PM-Timer running at invalid rate: %lu%% "
                  "of normal - aborting.\n",
                  100UL * delta / PMTMR_EXPECTED_RATE);
            return -1;
      }

      return 0;
}
#else
#define verify_pmtmr_rate() (0)
#endif

static int __init init_acpi_pm_clocksource(void)
{
      u32 value1, value2;
      unsigned int i;

      if (!pmtmr_ioport)
            return -ENODEV;

      clocksource_acpi_pm.mult = clocksource_hz2mult(PMTMR_TICKS_PER_SEC,
                                    clocksource_acpi_pm.shift);

      /* "verify" this timing source: */
      value1 = read_pmtmr();
      for (i = 0; i < 10000; i++) {
            value2 = read_pmtmr();
            if (value2 == value1)
                  continue;
            if (value2 > value1)
                  goto pm_good;
            if ((value2 < value1) && ((value2) < 0xFFF))
                  goto pm_good;
            printk(KERN_INFO "PM-Timer had inconsistent results:"
                  " 0x%#x, 0x%#x - aborting.\n", value1, value2);
            return -EINVAL;
      }
      printk(KERN_INFO "PM-Timer had no reasonable result:"
                  " 0x%#x - aborting.\n", value1);
      return -ENODEV;

pm_good:
      if (verify_pmtmr_rate() != 0)
            return -ENODEV;

      return clocksource_register(&clocksource_acpi_pm);
}

/* We use fs_initcall because we want the PCI fixups to have run
 * but we still need to load before device_initcall
 */
fs_initcall(init_acpi_pm_clocksource);

Generated by  Doxygen 1.6.0   Back to index