arch/i386/kernel/timers/timer_pm.c

   1 /*
   2  * (C) Dominik Brodowski <linux@brodo.de> 2003
   3  *
   4  * Driver to use the Power Management Timer (PMTMR) available in some
   5  * southbridges as primary timing source for the Linux kernel.
   6  *
   7  * Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c,
   8  * timer_hpet.c, and on Arjan van de Ven's implementation for 2.4.
   9  *
  10  * This file is licensed under the GPL v2.
  11  */
  12
  13
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/device.h>
  17 #include <linux/init.h>
  18 #include <asm/types.h>
  19 #include <asm/timer.h>
  20 #include <asm/smp.h>
  21 #include <asm/io.h>
  22 #include <asm/arch_hooks.h>
  23
  24 #include <linux/timex.h>
  25 #include "mach_timer.h"
  26
  27 /* Number of PMTMR ticks expected during calibration run */
  28 #define PMTMR_TICKS_PER_SEC 3579545
  29 #define PMTMR_EXPECTED_RATE \
  30   ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))
  31
  32
  33 /* The I/O port the PMTMR resides at.
  34  * The location is detected during setup_arch(),
  35  * in arch/i386/acpi/boot.c */
  36 u32 pmtmr_ioport = 0;
  37
  38
  39 /* value of the Power timer at last timer interrupt */
  40 static u32 offset_tick;
  41 static u32 offset_delay;
  42
  43 static unsigned long long monotonic_base;
  44 static seqlock_t monotonic_lock = SEQLOCK_UNLOCKED;
  45
  46 #define ACPI_PM_MASK 0xFFFFFF /* limit it to 24 bits */
  47
  48 /*helper function to safely read acpi pm timesource*/
  49 static inline u32 read_pmtmr(void)
  50 {
  51         u32 v1=0,v2=0,v3=0;
  52         /* It has been reported that because of various broken
  53          * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM time
  54          * source is not latched, so you must read it multiple
  55          * times to insure a safe value is read.
  56          */
  57         do {
  58                 v1 = inl(pmtmr_ioport);
  59                 v2 = inl(pmtmr_ioport);
  60                 v3 = inl(pmtmr_ioport);
  61         } while ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
  62                         || (v3 > v1 && v3 < v2));
  63
  64         /* mask the output to 24 bits */
  65         return v2 & ACPI_PM_MASK;
  66 }
  67
  68
  69 /*
  70  * Some boards have the PMTMR running way too fast. We check
  71  * the PMTMR rate against PIT channel 2 to catch these cases.
  72  */
  73 static int verify_pmtmr_rate(void)
  74 {
  75         u32 value1, value2;
  76         unsigned long count, delta;
  77
  78         mach_prepare_counter();
  79         value1 = read_pmtmr();
  80         mach_countup(&count);
  81         value2 = read_pmtmr();
  82         delta = (value2 - value1) & ACPI_PM_MASK;
  83
  84         /* Check that the PMTMR delta is within 5% of what we expect */
  85         if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 ||
  86             delta > (PMTMR_EXPECTED_RATE * 21) / 20) {
  87                 printk(KERN_INFO "PM-Timer running at invalid rate: %lu%% of normal - aborting.\n", 100UL * delta / PMTMR_EXPECTED_RATE);
  88                 return -1;
  89         }
  90
  91         return 0;
  92 }
  93
  94
  95 static int init_pmtmr(char* override)
  96 {
  97         u32 value1, value2;
  98         unsigned int i;
  99
 100         if (override[0] && strncmp(override,"pmtmr",5))
 101                 return -ENODEV;
 102
 103         if (!pmtmr_ioport)
 104                 return -ENODEV;
 105
 106         /* we use the TSC for delay_pmtmr, so make sure it exists */
 107         if (!cpu_has_tsc)
 108                 return -ENODEV;
 109
 110         /* "verify" this timing source */
 111         value1 = read_pmtmr();
 112         for (i = 0; i < 10000; i++) {
 113                 value2 = read_pmtmr();
 114                 if (value2 == value1)
 115                         continue;
 116                 if (value2 > value1)
 117                         goto pm_good;
 118                 if ((value2 < value1) && ((value2) < 0xFFF))
 119                         goto pm_good;
 120                 printk(KERN_INFO "PM-Timer had inconsistent results: 0x%#x, 0x%#x - aborting.\n", value1, value2);
 121                 return -EINVAL;
 122         }
 123         printk(KERN_INFO "PM-Timer had no reasonable result: 0x%#x - aborting.\n", value1);
 124         return -ENODEV;
 125
 126 pm_good:
 127         if (verify_pmtmr_rate() != 0)
 128                 return -ENODEV;
 129
 130         init_cpu_khz();
 131         return 0;
 132 }
 133
 134 static inline u32 cyc2us(u32 cycles)
 135 {
 136         /* The Power Management Timer ticks at 3.579545 ticks per microsecond.
 137          * 1 / PM_TIMER_FREQUENCY == 0.27936511 =~ 286/1024 [error: 0.024%]
 138          *
 139          * Even with HZ = 100, delta is at maximum 35796 ticks, so it can
 140          * easily be multiplied with 286 (=0x11E) without having to fear
 141          * u32 overflows.
 142          */
 143         cycles *= 286;
 144         return (cycles >> 10);
 145 }
 146
 147 /*
 148  * this gets called during each timer interrupt
 149  *   - Called while holding the writer xtime_lock
 150  */
 151 static void mark_offset_pmtmr(void)
 152 {
 153         u32 lost, delta, last_offset;
 154         static int first_run = 1;
 155         last_offset = offset_tick;
 156
 157         write_seqlock(&monotonic_lock);
 158
 159         offset_tick = read_pmtmr();
 160
 161         /* calculate tick interval */
 162         delta = (offset_tick - last_offset) & ACPI_PM_MASK;
 163
 164         /* convert to usecs */
 165         delta = cyc2us(delta);
 166
 167         /* update the monotonic base value */
 168         monotonic_base += delta * NSEC_PER_USEC;
 169         write_sequnlock(&monotonic_lock);
 170
 171         /* convert to ticks */
 172         delta += offset_delay;
 173         lost = delta / (USEC_PER_SEC / HZ);
 174         offset_delay = delta % (USEC_PER_SEC / HZ);
 175
 176
 177         /* compensate for lost ticks */
 178         if (lost >= 2)
 179                 jiffies_64 += lost - 1;
 180
 181         /* don't calculate delay for first run,
 182            or if we've got less then a tick */
 183         if (first_run || (lost < 1)) {
 184                 first_run = 0;
 185                 offset_delay = 0;
 186         }
 187 }
 188
 189
 190 static unsigned long long monotonic_clock_pmtmr(void)
 191 {
 192         u32 last_offset, this_offset;
 193         unsigned long long base, ret;
 194         unsigned seq;
 195
 196
 197         /* atomically read monotonic base & last_offset */
 198         do {
 199                 seq = read_seqbegin(&monotonic_lock);
 200                 last_offset = offset_tick;
 201                 base = monotonic_base;
 202         } while (read_seqretry(&monotonic_lock, seq));
 203
 204         /* Read the pmtmr */
 205         this_offset =  read_pmtmr();
 206
 207         /* convert to nanoseconds */
 208         ret = (this_offset - last_offset) & ACPI_PM_MASK;
 209         ret = base + (cyc2us(ret) * NSEC_PER_USEC);
 210         return ret;
 211 }
 212
 213 static void delay_pmtmr(unsigned long loops)
 214 {
 215         unsigned long bclock, now;
 216
 217         rdtscl(bclock);
 218         do
 219         {
 220                 rep_nop();
 221                 rdtscl(now);
 222         } while ((now-bclock) < loops);
 223 }
 224
 225
 226 /*
 227  * get the offset (in microseconds) from the last call to mark_offset()
 228  *      - Called holding a reader xtime_lock
 229  */
 230 static unsigned long get_offset_pmtmr(void)
 231 {
 232         u32 now, offset, delta = 0;
 233
 234         offset = offset_tick;
 235         now = read_pmtmr();
 236         delta = (now - offset)&ACPI_PM_MASK;
 237
 238         return (unsigned long) offset_delay + cyc2us(delta);
 239 }
 240
 241
 242 /* acpi timer_opts struct */
 243 static struct timer_opts timer_pmtmr = {
 244         .name                   = "pmtmr",
 245         .mark_offset            = mark_offset_pmtmr,
 246         .get_offset             = get_offset_pmtmr,
 247         .monotonic_clock        = monotonic_clock_pmtmr,
 248         .delay                  = delay_pmtmr,
 249 };
 250
 251 struct init_timer_opts __initdata timer_pmtmr_init = {
 252         .init = init_pmtmr,
 253         .opts = &timer_pmtmr,
 254 };
 255
 256 MODULE_LICENSE("GPL");
 257 MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
 258 MODULE_DESCRIPTION("Power Management Timer (PMTMR) as primary timing source for x86");