drivers/clocksource/acpi_pm.c

   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  */
  32 u32 pmtmr_ioport __read_mostly;
  33
  34 static inline u32 read_pmtmr(void)
  35 {
  36         /* mask the output to 24 bits */
  37         return inl(pmtmr_ioport) & ACPI_PM_MASK;
  38 }
  39
  40 u32 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
  60 static cycle_t acpi_pm_read_slow(void)
  61 {
  62         return (cycle_t)acpi_pm_read_verified();
  63 }
  64
  65 static cycle_t acpi_pm_read(void)
  66 {
  67         return (cycle_t)read_pmtmr();
  68 }
  69
  70 static 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
  83 static int __devinitdata acpi_pm_good;
  84 static 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
  91 static 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  */
 107 static 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 }
 122 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3,
 123                         acpi_pm_check_blacklist);
 124
 125 static 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 }
 139 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82801DB_0,
 140                         acpi_pm_check_graylist);
 141 DECLARE_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  */
 153 static 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
 184 static 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  */
 228 fs_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  */
 234 static int __init parse_pmtmr(char *arg)
 235 {
 236         unsigned long base;
 237
 238         if (strict_strtoul(arg, 16, &base))
 239                 return -EINVAL;
 240
 241         printk(KERN_INFO "PMTMR IOPort override: 0x%04x -> 0x%04lx\n",
 242                (unsigned int)pmtmr_ioport, base);
 243         pmtmr_ioport = base;
 244
 245         return 1;
 246 }
 247 __setup("pmtmr=", parse_pmtmr);