arch/x86/kernel/tsc_64.c

   1 #include <linux/kernel.h>
   2 #include <linux/sched.h>
   3 #include <linux/interrupt.h>
   4 #include <linux/init.h>
   5 #include <linux/clocksource.h>
   6 #include <linux/time.h>
   7 #include <linux/acpi.h>
   8 #include <linux/cpufreq.h>
   9 #include <linux/acpi_pmtmr.h>
  10
  11 #include <asm/hpet.h>
  12 #include <asm/timex.h>
  13 #include <asm/timer.h>
  14
  15 static int notsc __initdata = 0;
  16
  17 unsigned int cpu_khz;           /* TSC clocks / usec, not used here */
  18 EXPORT_SYMBOL(cpu_khz);
  19 unsigned int tsc_khz;
  20 EXPORT_SYMBOL(tsc_khz);
  21
  22 /* Accelerators for sched_clock()
  23  * convert from cycles(64bits) => nanoseconds (64bits)
  24  *  basic equation:
  25  *              ns = cycles / (freq / ns_per_sec)
  26  *              ns = cycles * (ns_per_sec / freq)
  27  *              ns = cycles * (10^9 / (cpu_khz * 10^3))
  28  *              ns = cycles * (10^6 / cpu_khz)
  29  *
  30  *      Then we use scaling math (suggested by george@mvista.com) to get:
  31  *              ns = cycles * (10^6 * SC / cpu_khz) / SC
  32  *              ns = cycles * cyc2ns_scale / SC
  33  *
  34  *      And since SC is a constant power of two, we can convert the div
  35  *  into a shift.
  36  *
  37  *  We can use khz divisor instead of mhz to keep a better precision, since
  38  *  cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
  39  *  (mathieu.desnoyers@polymtl.ca)
  40  *
  41  *                      -johnstul@us.ibm.com "math is hard, lets go shopping!"
  42  */
  43 DEFINE_PER_CPU(unsigned long, cyc2ns);
  44
  45 static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
  46 {
  47         unsigned long flags, prev_scale, *scale;
  48         unsigned long long tsc_now, ns_now;
  49
  50         local_irq_save(flags);
  51         sched_clock_idle_sleep_event();
  52
  53         scale = &per_cpu(cyc2ns, cpu);
  54
  55         rdtscll(tsc_now);
  56         ns_now = __cycles_2_ns(tsc_now);
  57
  58         prev_scale = *scale;
  59         if (cpu_khz)
  60                 *scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;
  61
  62         sched_clock_idle_wakeup_event(0);
  63         local_irq_restore(flags);
  64 }
  65
  66 unsigned long long native_sched_clock(void)
  67 {
  68         unsigned long a = 0;
  69
  70         /* Could do CPU core sync here. Opteron can execute rdtsc speculatively,
  71          * which means it is not completely exact and may not be monotonous
  72          * between CPUs. But the errors should be too small to matter for
  73          * scheduling purposes.
  74          */
  75
  76         rdtscll(a);
  77         return cycles_2_ns(a);
  78 }
  79
  80 /* We need to define a real function for sched_clock, to override the
  81    weak default version */
  82 #ifdef CONFIG_PARAVIRT
  83 unsigned long long sched_clock(void)
  84 {
  85         return paravirt_sched_clock();
  86 }
  87 #else
  88 unsigned long long
  89 sched_clock(void) __attribute__((alias("native_sched_clock")));
  90 #endif
  91
  92
  93 static int tsc_unstable;
  94
  95 int check_tsc_unstable(void)
  96 {
  97         return tsc_unstable;
  98 }
  99 EXPORT_SYMBOL_GPL(check_tsc_unstable);
 100
 101 #ifdef CONFIG_CPU_FREQ
 102
 103 /* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
 104  * changes.
 105  *
 106  * RED-PEN: On SMP we assume all CPUs run with the same frequency.  It's
 107  * not that important because current Opteron setups do not support
 108  * scaling on SMP anyroads.
 109  *
 110  * Should fix up last_tsc too. Currently gettimeofday in the
 111  * first tick after the change will be slightly wrong.
 112  */
 113
 114 static unsigned int  ref_freq;
 115 static unsigned long loops_per_jiffy_ref;
 116 static unsigned long tsc_khz_ref;
 117
 118 static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
 119                                  void *data)
 120 {
 121         struct cpufreq_freqs *freq = data;
 122         unsigned long *lpj, dummy;
 123
 124         if (cpu_has(&cpu_data(freq->cpu), X86_FEATURE_CONSTANT_TSC))
 125                 return 0;
 126
 127         lpj = &dummy;
 128         if (!(freq->flags & CPUFREQ_CONST_LOOPS))
 129 #ifdef CONFIG_SMP
 130                 lpj = &cpu_data(freq->cpu).loops_per_jiffy;
 131 #else
 132                 lpj = &boot_cpu_data.loops_per_jiffy;
 133 #endif
 134
 135         if (!ref_freq) {
 136                 ref_freq = freq->old;
 137                 loops_per_jiffy_ref = *lpj;
 138                 tsc_khz_ref = tsc_khz;
 139         }
 140         if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
 141                 (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
 142                 (val == CPUFREQ_RESUMECHANGE)) {
 143                 *lpj =
 144                 cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
 145
 146                 tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new);
 147                 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
 148                         mark_tsc_unstable("cpufreq changes");
 149         }
 150
 151         set_cyc2ns_scale(tsc_khz_ref, freq->cpu);
 152
 153         return 0;
 154 }
 155
 156 static struct notifier_block time_cpufreq_notifier_block = {
 157         .notifier_call  = time_cpufreq_notifier
 158 };
 159
 160 static int __init cpufreq_tsc(void)
 161 {
 162         cpufreq_register_notifier(&time_cpufreq_notifier_block,
 163                                   CPUFREQ_TRANSITION_NOTIFIER);
 164         return 0;
 165 }
 166
 167 core_initcall(cpufreq_tsc);
 168
 169 #endif
 170
 171 #define MAX_RETRIES     5
 172 #define SMI_TRESHOLD    50000
 173
 174 /*
 175  * Read TSC and the reference counters. Take care of SMI disturbance
 176  */
 177 static unsigned long __init tsc_read_refs(unsigned long *pm,
 178                                           unsigned long *hpet)
 179 {
 180         unsigned long t1, t2;
 181         int i;
 182
 183         for (i = 0; i < MAX_RETRIES; i++) {
 184                 t1 = get_cycles();
 185                 if (hpet)
 186                         *hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
 187                 else
 188                         *pm = acpi_pm_read_early();
 189                 t2 = get_cycles();
 190                 if ((t2 - t1) < SMI_TRESHOLD)
 191                         return t2;
 192         }
 193         return ULONG_MAX;
 194 }
 195
 196 /**
 197  * tsc_calibrate - calibrate the tsc on boot
 198  */
 199 void __init tsc_calibrate(void)
 200 {
 201         unsigned long flags, tsc1, tsc2, tr1, tr2, pm1, pm2, hpet1, hpet2;
 202         int hpet = is_hpet_enabled(), cpu;
 203
 204         local_irq_save(flags);
 205
 206         tsc1 = tsc_read_refs(&pm1, hpet ? &hpet1 : NULL);
 207
 208         outb((inb(0x61) & ~0x02) | 0x01, 0x61);
 209
 210         outb(0xb0, 0x43);
 211         outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
 212         outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42);
 213         tr1 = get_cycles();
 214         while ((inb(0x61) & 0x20) == 0);
 215         tr2 = get_cycles();
 216
 217         tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL);
 218
 219         local_irq_restore(flags);
 220
 221         /*
 222          * Preset the result with the raw and inaccurate PIT
 223          * calibration value
 224          */
 225         tsc_khz = (tr2 - tr1) / 50;
 226
 227         /* hpet or pmtimer available ? */
 228         if (!hpet && !pm1 && !pm2) {
 229                 printk(KERN_INFO "TSC calibrated against PIT\n");
 230                 return;
 231         }
 232
 233         /* Check, whether the sampling was disturbed by an SMI */
 234         if (tsc1 == ULONG_MAX || tsc2 == ULONG_MAX) {
 235                 printk(KERN_WARNING "TSC calibration disturbed by SMI, "
 236                        "using PIT calibration result\n");
 237                 return;
 238         }
 239
 240         tsc2 = (tsc2 - tsc1) * 1000000L;
 241
 242         if (hpet) {
 243                 printk(KERN_INFO "TSC calibrated against HPET\n");
 244                 if (hpet2 < hpet1)
 245                         hpet2 += 0x100000000;
 246                 hpet2 -= hpet1;
 247                 tsc1 = (hpet2 * hpet_readl(HPET_PERIOD)) / 1000000;
 248         } else {
 249                 printk(KERN_INFO "TSC calibrated against PM_TIMER\n");
 250                 if (pm2 < pm1)
 251                         pm2 += ACPI_PM_OVRRUN;
 252                 pm2 -= pm1;
 253                 tsc1 = (pm2 * 1000000000) / PMTMR_TICKS_PER_SEC;
 254         }
 255
 256         tsc_khz = tsc2 / tsc1;
 257
 258         for_each_possible_cpu(cpu)
 259                 set_cyc2ns_scale(tsc_khz, cpu);
 260 }
 261
 262 /*
 263  * Make an educated guess if the TSC is trustworthy and synchronized
 264  * over all CPUs.
 265  */
 266 __cpuinit int unsynchronized_tsc(void)
 267 {
 268         if (tsc_unstable)
 269                 return 1;
 270
 271 #ifdef CONFIG_SMP
 272         if (apic_is_clustered_box())
 273                 return 1;
 274 #endif
 275
 276         if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
 277                 return 0;
 278
 279         /* Assume multi socket systems are not synchronized */
 280         return num_present_cpus() > 1;
 281 }
 282
 283 int __init notsc_setup(char *s)
 284 {
 285         notsc = 1;
 286         return 1;
 287 }
 288
 289 __setup("notsc", notsc_setup);
 290
 291
 292 /* clock source code: */
 293 static cycle_t read_tsc(void)
 294 {
 295         cycle_t ret = (cycle_t)get_cycles();
 296         return ret;
 297 }
 298
 299 static cycle_t __vsyscall_fn vread_tsc(void)
 300 {
 301         cycle_t ret = (cycle_t)vget_cycles();
 302         return ret;
 303 }
 304
 305 static struct clocksource clocksource_tsc = {
 306         .name                   = "tsc",
 307         .rating                 = 300,
 308         .read                   = read_tsc,
 309         .mask                   = CLOCKSOURCE_MASK(64),
 310         .shift                  = 22,
 311         .flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
 312                                   CLOCK_SOURCE_MUST_VERIFY,
 313         .vread                  = vread_tsc,
 314 };
 315
 316 void mark_tsc_unstable(char *reason)
 317 {
 318         if (!tsc_unstable) {
 319                 tsc_unstable = 1;
 320                 printk("Marking TSC unstable due to %s\n", reason);
 321                 /* Change only the rating, when not registered */
 322                 if (clocksource_tsc.mult)
 323                         clocksource_change_rating(&clocksource_tsc, 0);
 324                 else
 325                         clocksource_tsc.rating = 0;
 326         }
 327 }
 328 EXPORT_SYMBOL_GPL(mark_tsc_unstable);
 329
 330 void __init init_tsc_clocksource(void)
 331 {
 332         if (!notsc) {
 333                 clocksource_tsc.mult = clocksource_khz2mult(tsc_khz,
 334                                                         clocksource_tsc.shift);
 335                 if (check_tsc_unstable())
 336                         clocksource_tsc.rating = 0;
 337
 338                 clocksource_register(&clocksource_tsc);
 339         }
 340 }