err.no Git - linux-2.6/blob - arch/ia64/kernel/time.c

   1 /*
   2  * linux/arch/ia64/kernel/time.c
   3  *
   4  * Copyright (C) 1998-2003 Hewlett-Packard Co
   5  *      Stephane Eranian <eranian@hpl.hp.com>
   6  *      David Mosberger <davidm@hpl.hp.com>
   7  * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
   8  * Copyright (C) 1999-2000 VA Linux Systems
   9  * Copyright (C) 1999-2000 Walt Drummond <drummond@valinux.com>
  10  */
  11
  12 #include <linux/cpu.h>
  13 #include <linux/init.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/profile.h>
  17 #include <linux/sched.h>
  18 #include <linux/time.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/efi.h>
  21 #include <linux/timex.h>
  22 #include <linux/clocksource.h>
  23
  24 #include <asm/machvec.h>
  25 #include <asm/delay.h>
  26 #include <asm/hw_irq.h>
  27 #include <asm/ptrace.h>
  28 #include <asm/sal.h>
  29 #include <asm/sections.h>
  30 #include <asm/system.h>
  31
  32 #include "fsyscall_gtod_data.h"
  33
  34 static cycle_t itc_get_cycles(void);
  35
  36 struct fsyscall_gtod_data_t fsyscall_gtod_data = {
  37         .lock = SEQLOCK_UNLOCKED,
  38 };
  39
  40 struct itc_jitter_data_t itc_jitter_data;
  41
  42 volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
  43
  44 #ifdef CONFIG_IA64_DEBUG_IRQ
  45
  46 unsigned long last_cli_ip;
  47 EXPORT_SYMBOL(last_cli_ip);
  48
  49 #endif
  50
  51 static struct clocksource clocksource_itc = {
  52         .name           = "itc",
  53         .rating         = 350,
  54         .read           = itc_get_cycles,
  55         .mask           = CLOCKSOURCE_MASK(64),
  56         .mult           = 0, /*to be calculated*/
  57         .shift          = 16,
  58         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  59 };
  60 static struct clocksource *itc_clocksource;
  61
  62 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
  63
  64 #include <linux/kernel_stat.h>
  65
  66 extern cputime_t cycle_to_cputime(u64 cyc);
  67
  68 /*
  69  * Called from the context switch with interrupts disabled, to charge all
  70  * accumulated times to the current process, and to prepare accounting on
  71  * the next process.
  72  */
  73 void ia64_account_on_switch(struct task_struct *prev, struct task_struct *next)
  74 {
  75         struct thread_info *pi = task_thread_info(prev);
  76         struct thread_info *ni = task_thread_info(next);
  77         cputime_t delta_stime, delta_utime;
  78         __u64 now;
  79
  80         now = ia64_get_itc();
  81
  82         delta_stime = cycle_to_cputime(pi->ac_stime + (now - pi->ac_stamp));
  83         account_system_time(prev, 0, delta_stime);
  84         account_system_time_scaled(prev, delta_stime);
  85
  86         if (pi->ac_utime) {
  87                 delta_utime = cycle_to_cputime(pi->ac_utime);
  88                 account_user_time(prev, delta_utime);
  89                 account_user_time_scaled(prev, delta_utime);
  90         }
  91
  92         pi->ac_stamp = ni->ac_stamp = now;
  93         ni->ac_stime = ni->ac_utime = 0;
  94 }
  95
  96 /*
  97  * Account time for a transition between system, hard irq or soft irq state.
  98  * Note that this function is called with interrupts enabled.
  99  */
 100 void account_system_vtime(struct task_struct *tsk)
 101 {
 102         struct thread_info *ti = task_thread_info(tsk);
 103         unsigned long flags;
 104         cputime_t delta_stime;
 105         __u64 now;
 106
 107         local_irq_save(flags);
 108
 109         now = ia64_get_itc();
 110
 111         delta_stime = cycle_to_cputime(ti->ac_stime + (now - ti->ac_stamp));
 112         account_system_time(tsk, 0, delta_stime);
 113         account_system_time_scaled(tsk, delta_stime);
 114         ti->ac_stime = 0;
 115
 116         ti->ac_stamp = now;
 117
 118         local_irq_restore(flags);
 119 }
 120
 121 /*
 122  * Called from the timer interrupt handler to charge accumulated user time
 123  * to the current process.  Must be called with interrupts disabled.
 124  */
 125 void account_process_tick(struct task_struct *p, int user_tick)
 126 {
 127         struct thread_info *ti = task_thread_info(p);
 128         cputime_t delta_utime;
 129
 130         if (ti->ac_utime) {
 131                 delta_utime = cycle_to_cputime(ti->ac_utime);
 132                 account_user_time(p, delta_utime);
 133                 account_user_time_scaled(p, delta_utime);
 134                 ti->ac_utime = 0;
 135         }
 136 }
 137
 138 #endif /* CONFIG_VIRT_CPU_ACCOUNTING */
 139
 140 static irqreturn_t
 141 timer_interrupt (int irq, void *dev_id)
 142 {
 143         unsigned long new_itm;
 144
 145         if (unlikely(cpu_is_offline(smp_processor_id()))) {
 146                 return IRQ_HANDLED;
 147         }
 148
 149         platform_timer_interrupt(irq, dev_id);
 150
 151         new_itm = local_cpu_data->itm_next;
 152
 153         if (!time_after(ia64_get_itc(), new_itm))
 154                 printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
 155                        ia64_get_itc(), new_itm);
 156
 157         profile_tick(CPU_PROFILING);
 158
 159         while (1) {
 160                 update_process_times(user_mode(get_irq_regs()));
 161
 162                 new_itm += local_cpu_data->itm_delta;
 163
 164                 if (smp_processor_id() == time_keeper_id) {
 165                         /*
 166                          * Here we are in the timer irq handler. We have irqs locally
 167                          * disabled, but we don't know if the timer_bh is running on
 168                          * another CPU. We need to avoid to SMP race by acquiring the
 169                          * xtime_lock.
 170                          */
 171                         write_seqlock(&xtime_lock);
 172                         do_timer(1);
 173                         local_cpu_data->itm_next = new_itm;
 174                         write_sequnlock(&xtime_lock);
 175                 } else
 176                         local_cpu_data->itm_next = new_itm;
 177
 178                 if (time_after(new_itm, ia64_get_itc()))
 179                         break;
 180
 181                 /*
 182                  * Allow IPIs to interrupt the timer loop.
 183                  */
 184                 local_irq_enable();
 185                 local_irq_disable();
 186         }
 187
 188         do {
 189                 /*
 190                  * If we're too close to the next clock tick for
 191                  * comfort, we increase the safety margin by
 192                  * intentionally dropping the next tick(s).  We do NOT
 193                  * update itm.next because that would force us to call
 194                  * do_timer() which in turn would let our clock run
 195                  * too fast (with the potentially devastating effect
 196                  * of losing monotony of time).
 197                  */
 198                 while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
 199                         new_itm += local_cpu_data->itm_delta;
 200                 ia64_set_itm(new_itm);
 201                 /* double check, in case we got hit by a (slow) PMI: */
 202         } while (time_after_eq(ia64_get_itc(), new_itm));
 203         return IRQ_HANDLED;
 204 }
 205
 206 /*
 207  * Encapsulate access to the itm structure for SMP.
 208  */
 209 void
 210 ia64_cpu_local_tick (void)
 211 {
 212         int cpu = smp_processor_id();
 213         unsigned long shift = 0, delta;
 214
 215         /* arrange for the cycle counter to generate a timer interrupt: */
 216         ia64_set_itv(IA64_TIMER_VECTOR);
 217
 218         delta = local_cpu_data->itm_delta;
 219         /*
 220          * Stagger the timer tick for each CPU so they don't occur all at (almost) the
 221          * same time:
 222          */
 223         if (cpu) {
 224                 unsigned long hi = 1UL << ia64_fls(cpu);
 225                 shift = (2*(cpu - hi) + 1) * delta/hi/2;
 226         }
 227         local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
 228         ia64_set_itm(local_cpu_data->itm_next);
 229 }
 230
 231 static int nojitter;
 232
 233 static int __init nojitter_setup(char *str)
 234 {
 235         nojitter = 1;
 236         printk("Jitter checking for ITC timers disabled\n");
 237         return 1;
 238 }
 239
 240 __setup("nojitter", nojitter_setup);
 241
 242
 243 void __devinit
 244 ia64_init_itm (void)
 245 {
 246         unsigned long platform_base_freq, itc_freq;
 247         struct pal_freq_ratio itc_ratio, proc_ratio;
 248         long status, platform_base_drift, itc_drift;
 249
 250         /*
 251          * According to SAL v2.6, we need to use a SAL call to determine the platform base
 252          * frequency and then a PAL call to determine the frequency ratio between the ITC
 253          * and the base frequency.
 254          */
 255         status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
 256                                     &platform_base_freq, &platform_base_drift);
 257         if (status != 0) {
 258                 printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
 259         } else {
 260                 status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
 261                 if (status != 0)
 262                         printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
 263         }
 264         if (status != 0) {
 265                 /* invent "random" values */
 266                 printk(KERN_ERR
 267                        "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
 268                 platform_base_freq = 100000000;
 269                 platform_base_drift = -1;       /* no drift info */
 270                 itc_ratio.num = 3;
 271                 itc_ratio.den = 1;
 272         }
 273         if (platform_base_freq < 40000000) {
 274                 printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
 275                        platform_base_freq);
 276                 platform_base_freq = 75000000;
 277                 platform_base_drift = -1;
 278         }
 279         if (!proc_ratio.den)
 280                 proc_ratio.den = 1;     /* avoid division by zero */
 281         if (!itc_ratio.den)
 282                 itc_ratio.den = 1;      /* avoid division by zero */
 283
 284         itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
 285
 286         local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
 287         printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
 288                "ITC freq=%lu.%03luMHz", smp_processor_id(),
 289                platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
 290                itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
 291
 292         if (platform_base_drift != -1) {
 293                 itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
 294                 printk("+/-%ldppm\n", itc_drift);
 295         } else {
 296                 itc_drift = -1;
 297                 printk("\n");
 298         }
 299
 300         local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
 301         local_cpu_data->itc_freq = itc_freq;
 302         local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
 303         local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
 304                                         + itc_freq/2)/itc_freq;
 305
 306         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
 307 #ifdef CONFIG_SMP
 308                 /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
 309                  * Jitter compensation requires a cmpxchg which may limit
 310                  * the scalability of the syscalls for retrieving time.
 311                  * The ITC synchronization is usually successful to within a few
 312                  * ITC ticks but this is not a sure thing. If you need to improve
 313                  * timer performance in SMP situations then boot the kernel with the
 314                  * "nojitter" option. However, doing so may result in time fluctuating (maybe
 315                  * even going backward) if the ITC offsets between the individual CPUs
 316                  * are too large.
 317                  */
 318                 if (!nojitter)
 319                         itc_jitter_data.itc_jitter = 1;
 320 #endif
 321         } else
 322                 /*
 323                  * ITC is drifty and we have not synchronized the ITCs in smpboot.c.
 324                  * ITC values may fluctuate significantly between processors.
 325                  * Clock should not be used for hrtimers. Mark itc as only
 326                  * useful for boot and testing.
 327                  *
 328                  * Note that jitter compensation is off! There is no point of
 329                  * synchronizing ITCs since they may be large differentials
 330                  * that change over time.
 331                  *
 332                  * The only way to fix this would be to repeatedly sync the
 333                  * ITCs. Until that time we have to avoid ITC.
 334                  */
 335                 clocksource_itc.rating = 50;
 336
 337         /* Setup the CPU local timer tick */
 338         ia64_cpu_local_tick();
 339
 340         if (!itc_clocksource) {
 341                 /* Sort out mult/shift values: */
 342                 clocksource_itc.mult =
 343                         clocksource_hz2mult(local_cpu_data->itc_freq,
 344                                                 clocksource_itc.shift);
 345                 clocksource_register(&clocksource_itc);
 346                 itc_clocksource = &clocksource_itc;
 347         }
 348 }
 349
 350 static cycle_t itc_get_cycles(void)
 351 {
 352         u64 lcycle, now, ret;
 353
 354         if (!itc_jitter_data.itc_jitter)
 355                 return get_cycles();
 356
 357         lcycle = itc_jitter_data.itc_lastcycle;
 358         now = get_cycles();
 359         if (lcycle && time_after(lcycle, now))
 360                 return lcycle;
 361
 362         /*
 363          * Keep track of the last timer value returned.
 364          * In an SMP environment, you could lose out in contention of
 365          * cmpxchg. If so, your cmpxchg returns new value which the
 366          * winner of contention updated to. Use the new value instead.
 367          */
 368         ret = cmpxchg(&itc_jitter_data.itc_lastcycle, lcycle, now);
 369         if (unlikely(ret != lcycle))
 370                 return ret;
 371
 372         return now;
 373 }
 374
 375
 376 static struct irqaction timer_irqaction = {
 377         .handler =      timer_interrupt,
 378         .flags =        IRQF_DISABLED | IRQF_IRQPOLL,
 379         .name =         "timer"
 380 };
 381
 382 void __devinit ia64_disable_timer(void)
 383 {
 384         ia64_set_itv(1 << 16);
 385 }
 386
 387 void __init
 388 time_init (void)
 389 {
 390         register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
 391         efi_gettimeofday(&xtime);
 392         ia64_init_itm();
 393
 394         /*
 395          * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
 396          * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
 397          */
 398         set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
 399 }
 400
 401 /*
 402  * Generic udelay assumes that if preemption is allowed and the thread
 403  * migrates to another CPU, that the ITC values are synchronized across
 404  * all CPUs.
 405  */
 406 static void
 407 ia64_itc_udelay (unsigned long usecs)
 408 {
 409         unsigned long start = ia64_get_itc();
 410         unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
 411
 412         while (time_before(ia64_get_itc(), end))
 413                 cpu_relax();
 414 }
 415
 416 void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
 417
 418 void
 419 udelay (unsigned long usecs)
 420 {
 421         (*ia64_udelay)(usecs);
 422 }
 423 EXPORT_SYMBOL(udelay);
 424
 425 /* IA64 doesn't cache the timezone */
 426 void update_vsyscall_tz(void)
 427 {
 428 }
 429
 430 void update_vsyscall(struct timespec *wall, struct clocksource *c)
 431 {
 432         unsigned long flags;
 433
 434         write_seqlock_irqsave(&fsyscall_gtod_data.lock, flags);
 435
 436         /* copy fsyscall clock data */
 437         fsyscall_gtod_data.clk_mask = c->mask;
 438         fsyscall_gtod_data.clk_mult = c->mult;
 439         fsyscall_gtod_data.clk_shift = c->shift;
 440         fsyscall_gtod_data.clk_fsys_mmio = c->fsys_mmio;
 441         fsyscall_gtod_data.clk_cycle_last = c->cycle_last;
 442
 443         /* copy kernel time structures */
 444         fsyscall_gtod_data.wall_time.tv_sec = wall->tv_sec;
 445         fsyscall_gtod_data.wall_time.tv_nsec = wall->tv_nsec;
 446         fsyscall_gtod_data.monotonic_time.tv_sec = wall_to_monotonic.tv_sec
 447                                                         + wall->tv_sec;
 448         fsyscall_gtod_data.monotonic_time.tv_nsec = wall_to_monotonic.tv_nsec
 449                                                         + wall->tv_nsec;
 450
 451         /* normalize */
 452         while (fsyscall_gtod_data.monotonic_time.tv_nsec >= NSEC_PER_SEC) {
 453                 fsyscall_gtod_data.monotonic_time.tv_nsec -= NSEC_PER_SEC;
 454                 fsyscall_gtod_data.monotonic_time.tv_sec++;
 455         }
 456
 457         write_sequnlock_irqrestore(&fsyscall_gtod_data.lock, flags);
 458 }
 459