linux/drivers/clocksource/acpi_pm.c
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   1/*
   2 * linux/drivers/clocksource/acpi_pm.c
   3 *
   4 * This file contains the ACPI PM based clocksource.
   5 *
   6 * This code was largely moved from the i386 timer_pm.c file
   7 * which was (C) Dominik Brodowski <linux@brodo.de> 2003
   8 * and contained the following comments:
   9 *
  10 * Driver to use the Power Management Timer (PMTMR) available in some
  11 * southbridges as primary timing source for the Linux kernel.
  12 *
  13 * Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c,
  14 * timer_hpet.c, and on Arjan van de Ven's implementation for 2.4.
  15 *
  16 * This file is licensed under the GPL v2.
  17 */
  18
  19#include <linux/acpi_pmtmr.h>
  20#include <linux/clocksource.h>
  21#include <linux/errno.h>
  22#include <linux/init.h>
  23#include <linux/pci.h>
  24#include <linux/delay.h>
  25#include <asm/io.h>
  26
  27/*
  28 * The I/O port the PMTMR resides at.
  29 * The location is detected during setup_arch(),
  30 * in arch/i386/kernel/acpi/boot.c
  31 */
  32u32 pmtmr_ioport __read_mostly;
  33
  34static inline u32 read_pmtmr(void)
  35{
  36        /* mask the output to 24 bits */
  37        return inl(pmtmr_ioport) & ACPI_PM_MASK;
  38}
  39
  40u32 acpi_pm_read_verified(void)
  41{
  42        u32 v1 = 0, v2 = 0, v3 = 0;
  43
  44        /*
  45         * It has been reported that because of various broken
  46         * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM clock
  47         * source is not latched, you must read it multiple
  48         * times to ensure a safe value is read:
  49         */
  50        do {
  51                v1 = read_pmtmr();
  52                v2 = read_pmtmr();
  53                v3 = read_pmtmr();
  54        } while (unlikely((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
  55                          || (v3 > v1 && v3 < v2)));
  56
  57        return v2;
  58}
  59
  60static cycle_t acpi_pm_read_slow(void)
  61{
  62        return (cycle_t)acpi_pm_read_verified();
  63}
  64
  65static cycle_t acpi_pm_read(void)
  66{
  67        return (cycle_t)read_pmtmr();
  68}
  69
  70static struct clocksource clocksource_acpi_pm = {
  71        .name           = "acpi_pm",
  72        .rating         = 200,
  73        .read           = acpi_pm_read,
  74        .mask           = (cycle_t)ACPI_PM_MASK,
  75        .mult           = 0, /*to be calculated*/
  76        .shift          = 22,
  77        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  78
  79};
  80
  81
  82#ifdef CONFIG_PCI
  83static int __devinitdata acpi_pm_good;
  84static int __init acpi_pm_good_setup(char *__str)
  85{
  86        acpi_pm_good = 1;
  87        return 1;
  88}
  89__setup("acpi_pm_good", acpi_pm_good_setup);
  90
  91static inline void acpi_pm_need_workaround(void)
  92{
  93        clocksource_acpi_pm.read = acpi_pm_read_slow;
  94        clocksource_acpi_pm.rating = 120;
  95}
  96
  97/*
  98 * PIIX4 Errata:
  99 *
 100 * The power management timer may return improper results when read.
 101 * Although the timer value settles properly after incrementing,
 102 * while incrementing there is a 3 ns window every 69.8 ns where the
 103 * timer value is indeterminate (a 4.2% chance that the data will be
 104 * incorrect when read). As a result, the ACPI free running count up
 105 * timer specification is violated due to erroneous reads.
 106 */
 107static void __devinit acpi_pm_check_blacklist(struct pci_dev *dev)
 108{
 109        if (acpi_pm_good)
 110                return;
 111
 112        /* the bug has been fixed in PIIX4M */
 113        if (dev->revision < 3) {
 114                printk(KERN_WARNING "* Found PM-Timer Bug on the chipset."
 115                       " Due to workarounds for a bug,\n"
 116                       "* this clock source is slow. Consider trying"
 117                       " other clock sources\n");
 118
 119                acpi_pm_need_workaround();
 120        }
 121}
 122DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3,
 123                        acpi_pm_check_blacklist);
 124
 125static void __devinit acpi_pm_check_graylist(struct pci_dev *dev)
 126{
 127        if (acpi_pm_good)
 128                return;
 129
 130        printk(KERN_WARNING "* The chipset may have PM-Timer Bug. Due to"
 131               " workarounds for a bug,\n"
 132               "* this clock source is slow. If you are sure your timer"
 133               " does not have\n"
 134               "* this bug, please use \"acpi_pm_good\" to disable the"
 135               " workaround\n");
 136
 137        acpi_pm_need_workaround();
 138}
 139DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82801DB_0,
 140                        acpi_pm_check_graylist);
 141DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_LE,
 142                        acpi_pm_check_graylist);
 143#endif
 144
 145#ifndef CONFIG_X86_64
 146#include "mach_timer.h"
 147#define PMTMR_EXPECTED_RATE \
 148  ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))
 149/*
 150 * Some boards have the PMTMR running way too fast. We check
 151 * the PMTMR rate against PIT channel 2 to catch these cases.
 152 */
 153static int verify_pmtmr_rate(void)
 154{
 155        cycle_t value1, value2;
 156        unsigned long count, delta;
 157
 158        mach_prepare_counter();
 159        value1 = clocksource_acpi_pm.read();
 160        mach_countup(&count);
 161        value2 = clocksource_acpi_pm.read();
 162        delta = (value2 - value1) & ACPI_PM_MASK;
 163
 164        /* Check that the PMTMR delta is within 5% of what we expect */
 165        if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 ||
 166            delta > (PMTMR_EXPECTED_RATE * 21) / 20) {
 167                printk(KERN_INFO "PM-Timer running at invalid rate: %lu%% "
 168                        "of normal - aborting.\n",
 169                        100UL * delta / PMTMR_EXPECTED_RATE);
 170                return -1;
 171        }
 172
 173        return 0;
 174}
 175#else
 176#define verify_pmtmr_rate() (0)
 177#endif
 178
 179/* Number of monotonicity checks to perform during initialization */
 180#define ACPI_PM_MONOTONICITY_CHECKS 10
 181/* Number of reads we try to get two different values */
 182#define ACPI_PM_READ_CHECKS 10000
 183
 184static int __init init_acpi_pm_clocksource(void)
 185{
 186        cycle_t value1, value2;
 187        unsigned int i, j = 0;
 188
 189        if (!pmtmr_ioport)
 190                return -ENODEV;
 191
 192        clocksource_acpi_pm.mult = clocksource_hz2mult(PMTMR_TICKS_PER_SEC,
 193                                                clocksource_acpi_pm.shift);
 194
 195        /* "verify" this timing source: */
 196        for (j = 0; j < ACPI_PM_MONOTONICITY_CHECKS; j++) {
 197                udelay(100 * j);
 198                value1 = clocksource_acpi_pm.read();
 199                for (i = 0; i < ACPI_PM_READ_CHECKS; i++) {
 200                        value2 = clocksource_acpi_pm.read();
 201                        if (value2 == value1)
 202                                continue;
 203                        if (value2 > value1)
 204                                break;
 205                        if ((value2 < value1) && ((value2) < 0xFFF))
 206                                break;
 207                        printk(KERN_INFO "PM-Timer had inconsistent results:"
 208                               " 0x%#llx, 0x%#llx - aborting.\n",
 209                               value1, value2);
 210                        return -EINVAL;
 211                }
 212                if (i == ACPI_PM_READ_CHECKS) {
 213                        printk(KERN_INFO "PM-Timer failed consistency check "
 214                               " (0x%#llx) - aborting.\n", value1);
 215                        return -ENODEV;
 216                }
 217        }
 218
 219        if (verify_pmtmr_rate() != 0)
 220                return -ENODEV;
 221
 222        return clocksource_register(&clocksource_acpi_pm);
 223}
 224
 225/* We use fs_initcall because we want the PCI fixups to have run
 226 * but we still need to load before device_initcall
 227 */
 228fs_initcall(init_acpi_pm_clocksource);
 229
 230/*
 231 * Allow an override of the IOPort. Stupid BIOSes do not tell us about
 232 * the PMTimer, but we might know where it is.
 233 */
 234static int __init parse_pmtmr(char *arg)
 235{
 236        unsigned long base;
 237
 238        if (strict_strtoul(arg, 16, &base))
 239                return -EINVAL;
 240#ifdef CONFIG_X86_64
 241        if (base > UINT_MAX)
 242                return -ERANGE;
 243#endif
 244        printk(KERN_INFO "PMTMR IOPort override: 0x%04x -> 0x%04lx\n",
 245               pmtmr_ioport, base);
 246        pmtmr_ioport = base;
 247
 248        return 1;
 249}
 250__setup("pmtmr=", parse_pmtmr);
 251