acpi_pm.c

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/*
 * 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 <[email protected]> 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/timex.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/delay.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(struct clocksource *cs)
{
    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,
    .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 cycle_t acpi_pm_read_slow(struct clocksource *cs)
{
    return (cycle_t)acpi_pm_read_verified();
}

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 <asm/mach_timer.h>
#define PMTMR_EXPECTED_RATE \
  ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (PIT_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)
{
    cycle_t value1, value2;
    unsigned long count, delta;

    mach_prepare_counter();
    value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
    mach_countup(&count);
    value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
    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

/* Number of monotonicity checks to perform during initialization */
#define ACPI_PM_MONOTONICITY_CHECKS 10
/* Number of reads we try to get two different values */
#define ACPI_PM_READ_CHECKS 10000

static int __init init_acpi_pm_clocksource(void)
{
    cycle_t value1, value2;
    unsigned int i, j = 0;

    if (!pmtmr_ioport)
        return -ENODEV;

    /* "verify" this timing source: */
    for (j = 0; j < ACPI_PM_MONOTONICITY_CHECKS; j++) {
        udelay(100 * j);
        value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
        for (i = 0; i < ACPI_PM_READ_CHECKS; i++) {
            value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
            if (value2 == value1)
                continue;
            if (value2 > value1)
                break;
            if ((value2 < value1) && ((value2) < 0xFFF))
                break;
            printk(KERN_INFO "PM-Timer had inconsistent results:"
                   " 0x%#llx, 0x%#llx - aborting.\n",
                   value1, value2);
            pmtmr_ioport = 0;
            return -EINVAL;
        }
        if (i == ACPI_PM_READ_CHECKS) {
            printk(KERN_INFO "PM-Timer failed consistency check "
                   " (0x%#llx) - aborting.\n", value1);
            pmtmr_ioport = 0;
            return -ENODEV;
        }
    }

    if (verify_pmtmr_rate() != 0){
        pmtmr_ioport = 0;
        return -ENODEV;
    }

    return clocksource_register_hz(&clocksource_acpi_pm,
                        PMTMR_TICKS_PER_SEC);
}

/* 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);

/*
 * Allow an override of the IOPort. Stupid BIOSes do not tell us about
 * the PMTimer, but we might know where it is.
 */
static int __init parse_pmtmr(char *arg)
{
    unsigned long base;

    if (strict_strtoul(arg, 16, &base))
        return -EINVAL;
#ifdef CONFIG_X86_64
    if (base > UINT_MAX)
        return -ERANGE;
#endif
    printk(KERN_INFO "PMTMR IOPort override: 0x%04x -> 0x%04lx\n",
           pmtmr_ioport, base);
    pmtmr_ioport = base;

    return 1;
}
__setup("pmtmr=", parse_pmtmr);