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/paravirt.h>
  28 #include <asm/ptrace.h>
  29 #include <asm/sal.h>
  30 #include <asm/sections.h>
  31 #include <asm/system.h>
  32
  33 #include "fsyscall_gtod_data.h"
  34
  35 static cycle_t itc_get_cycles(void);
  36
  37 struct fsyscall_gtod_data_t fsyscall_gtod_data = {
  38         .lock = SEQLOCK_UNLOCKED,
  39 };
  40
  41 struct itc_jitter_data_t itc_jitter_data;
  42
  43 volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
  44
  45 #ifdef CONFIG_IA64_DEBUG_IRQ
  46
  47 unsigned long last_cli_ip;
  48 EXPORT_SYMBOL(last_cli_ip);
  49
  50 #endif
  51
  52 #ifdef CONFIG_PARAVIRT
  53 static void
  54 paravirt_clocksource_resume(void)
  55 {
  56         if (pv_time_ops.clocksource_resume)
  57                 pv_time_ops.clocksource_resume();
  58 }
  59 #endif
  60
  61 static struct clocksource clocksource_itc = {
  62         .name           = "itc",
  63         .rating         = 350,
  64         .read           = itc_get_cycles,
  65         .mask           = CLOCKSOURCE_MASK(64),
  66         .mult           = 0, /*to be calculated*/
  67         .shift          = 16,
  68         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  69 #ifdef CONFIG_PARAVIRT
  70         .resume         = paravirt_clocksource_resume,
  71 #endif
  72 };
  73 static struct clocksource *itc_clocksource;
  74
  75 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
  76
  77 #include <linux/kernel_stat.h>
  78
  79 extern cputime_t cycle_to_cputime(u64 cyc);
  80
  81 /*
  82  * Called from the context switch with interrupts disabled, to charge all
  83  * accumulated times to the current process, and to prepare accounting on
  84  * the next process.
  85  */
  86 void ia64_account_on_switch(struct task_struct *prev, struct task_struct *next)
  87 {
  88         struct thread_info *pi = task_thread_info(prev);
  89         struct thread_info *ni = task_thread_info(next);
  90         cputime_t delta_stime, delta_utime;
  91         __u64 now;
  92
  93         now = ia64_get_itc();
  94
  95         delta_stime = cycle_to_cputime(pi->ac_stime + (now - pi->ac_stamp));
  96         account_system_time(prev, 0, delta_stime);
  97         account_system_time_scaled(prev, delta_stime);
  98
  99         if (pi->ac_utime) {
 100                 delta_utime = cycle_to_cputime(pi->ac_utime);
 101                 account_user_time(prev, delta_utime);
 102                 account_user_time_scaled(prev, delta_utime);
 103         }
 104
 105         pi->ac_stamp = ni->ac_stamp = now;
 106         ni->ac_stime = ni->ac_utime = 0;
 107 }
 108
 109 /*
 110  * Account time for a transition between system, hard irq or soft irq state.
 111  * Note that this function is called with interrupts enabled.
 112  */
 113 void account_system_vtime(struct task_struct *tsk)
 114 {
 115         struct thread_info *ti = task_thread_info(tsk);
 116         unsigned long flags;
 117         cputime_t delta_stime;
 118         __u64 now;
 119
 120         local_irq_save(flags);
 121
 122         now = ia64_get_itc();
 123
 124         delta_stime = cycle_to_cputime(ti->ac_stime + (now - ti->ac_stamp));
 125         account_system_time(tsk, 0, delta_stime);
 126         account_system_time_scaled(tsk, delta_stime);
 127         ti->ac_stime = 0;
 128
 129         ti->ac_stamp = now;
 130
 131         local_irq_restore(flags);
 132 }
 133
 134 /*
 135  * Called from the timer interrupt handler to charge accumulated user time
 136  * to the current process.  Must be called with interrupts disabled.
 137  */
 138 void account_process_tick(struct task_struct *p, int user_tick)
 139 {
 140         struct thread_info *ti = task_thread_info(p);
 141         cputime_t delta_utime;
 142
 143         if (ti->ac_utime) {
 144                 delta_utime = cycle_to_cputime(ti->ac_utime);
 145                 account_user_time(p, delta_utime);
 146                 account_user_time_scaled(p, delta_utime);
 147                 ti->ac_utime = 0;
 148         }
 149 }
 150
 151 #endif /* CONFIG_VIRT_CPU_ACCOUNTING */
 152
 153 static irqreturn_t
 154 timer_interrupt (int irq, void *dev_id)
 155 {
 156         unsigned long new_itm;
 157
 158         if (unlikely(cpu_is_offline(smp_processor_id()))) {
 159                 return IRQ_HANDLED;
 160         }
 161
 162         platform_timer_interrupt(irq, dev_id);
 163
 164         new_itm = local_cpu_data->itm_next;
 165
 166         if (!time_after(ia64_get_itc(), new_itm))
 167                 printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
 168                        ia64_get_itc(), new_itm);
 169
 170         profile_tick(CPU_PROFILING);
 171
 172         if (paravirt_do_steal_accounting(&new_itm))
 173                 goto skip_process_time_accounting;
 174
 175         while (1) {
 176                 update_process_times(user_mode(get_irq_regs()));
 177
 178                 new_itm += local_cpu_data->itm_delta;
 179
 180                 if (smp_processor_id() == time_keeper_id) {
 181                         /*
 182                          * Here we are in the timer irq handler. We have irqs locally
 183                          * disabled, but we don't know if the timer_bh is running on
 184                          * another CPU. We need to avoid to SMP race by acquiring the
 185                          * xtime_lock.
 186                          */
 187                         write_seqlock(&xtime_lock);
 188                         do_timer(1);
 189                         local_cpu_data->itm_next = new_itm;
 190                         write_sequnlock(&xtime_lock);
 191                 } else
 192                         local_cpu_data->itm_next = new_itm;
 193
 194                 if (time_after(new_itm, ia64_get_itc()))
 195                         break;
 196
 197                 /*
 198                  * Allow IPIs to interrupt the timer loop.
 199                  */
 200                 local_irq_enable();
 201                 local_irq_disable();
 202         }
 203
 204 skip_process_time_accounting:
 205
 206         do {
 207                 /*
 208                  * If we're too close to the next clock tick for
 209                  * comfort, we increase the safety margin by
 210                  * intentionally dropping the next tick(s).  We do NOT
 211                  * update itm.next because that would force us to call
 212                  * do_timer() which in turn would let our clock run
 213                  * too fast (with the potentially devastating effect
 214                  * of losing monotony of time).
 215                  */
 216                 while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
 217                         new_itm += local_cpu_data->itm_delta;
 218                 ia64_set_itm(new_itm);
 219                 /* double check, in case we got hit by a (slow) PMI: */
 220         } while (time_after_eq(ia64_get_itc(), new_itm));
 221         return IRQ_HANDLED;
 222 }
 223
 224 /*
 225  * Encapsulate access to the itm structure for SMP.
 226  */
 227 void
 228 ia64_cpu_local_tick (void)
 229 {
 230         int cpu = smp_processor_id();
 231         unsigned long shift = 0, delta;
 232
 233         /* arrange for the cycle counter to generate a timer interrupt: */
 234         ia64_set_itv(IA64_TIMER_VECTOR);
 235
 236         delta = local_cpu_data->itm_delta;
 237         /*
 238          * Stagger the timer tick for each CPU so they don't occur all at (almost) the
 239          * same time:
 240          */
 241         if (cpu) {
 242                 unsigned long hi = 1UL << ia64_fls(cpu);
 243                 shift = (2*(cpu - hi) + 1) * delta/hi/2;
 244         }
 245         local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
 246         ia64_set_itm(local_cpu_data->itm_next);
 247 }
 248
 249 static int nojitter;
 250
 251 static int __init nojitter_setup(char *str)
 252 {
 253         nojitter = 1;
 254         printk("Jitter checking for ITC timers disabled\n");
 255         return 1;
 256 }
 257
 258 __setup("nojitter", nojitter_setup);
 259
 260
 261 void __devinit
 262 ia64_init_itm (void)
 263 {
 264         unsigned long platform_base_freq, itc_freq;
 265         struct pal_freq_ratio itc_ratio, proc_ratio;
 266         long status, platform_base_drift, itc_drift;
 267
 268         /*
 269          * According to SAL v2.6, we need to use a SAL call to determine the platform base
 270          * frequency and then a PAL call to determine the frequency ratio between the ITC
 271          * and the base frequency.
 272          */
 273         status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
 274                                     &platform_base_freq, &platform_base_drift);
 275         if (status != 0) {
 276                 printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
 277         } else {
 278                 status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
 279                 if (status != 0)
 280                         printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
 281         }
 282         if (status != 0) {
 283                 /* invent "random" values */
 284                 printk(KERN_ERR
 285                        "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
 286                 platform_base_freq = 100000000;
 287                 platform_base_drift = -1;       /* no drift info */
 288                 itc_ratio.num = 3;
 289                 itc_ratio.den = 1;
 290         }
 291         if (platform_base_freq < 40000000) {
 292                 printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
 293                        platform_base_freq);
 294                 platform_base_freq = 75000000;
 295                 platform_base_drift = -1;
 296         }
 297         if (!proc_ratio.den)
 298                 proc_ratio.den = 1;     /* avoid division by zero */
 299         if (!itc_ratio.den)
 300                 itc_ratio.den = 1;      /* avoid division by zero */
 301
 302         itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
 303
 304         local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
 305         printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
 306                "ITC freq=%lu.%03luMHz", smp_processor_id(),
 307                platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
 308                itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
 309
 310         if (platform_base_drift != -1) {
 311                 itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
 312                 printk("+/-%ldppm\n", itc_drift);
 313         } else {
 314                 itc_drift = -1;
 315                 printk("\n");
 316         }
 317
 318         local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
 319         local_cpu_data->itc_freq = itc_freq;
 320         local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
 321         local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
 322                                         + itc_freq/2)/itc_freq;
 323
 324         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
 325 #ifdef CONFIG_SMP
 326                 /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
 327                  * Jitter compensation requires a cmpxchg which may limit
 328                  * the scalability of the syscalls for retrieving time.
 329                  * The ITC synchronization is usually successful to within a few
 330                  * ITC ticks but this is not a sure thing. If you need to improve
 331                  * timer performance in SMP situations then boot the kernel with the
 332                  * "nojitter" option. However, doing so may result in time fluctuating (maybe
 333                  * even going backward) if the ITC offsets between the individual CPUs
 334                  * are too large.
 335                  */
 336                 if (!nojitter)
 337                         itc_jitter_data.itc_jitter = 1;
 338 #endif
 339         } else
 340                 /*
 341                  * ITC is drifty and we have not synchronized the ITCs in smpboot.c.
 342                  * ITC values may fluctuate significantly between processors.
 343                  * Clock should not be used for hrtimers. Mark itc as only
 344                  * useful for boot and testing.
 345                  *
 346                  * Note that jitter compensation is off! There is no point of
 347                  * synchronizing ITCs since they may be large differentials
 348                  * that change over time.
 349                  *
 350                  * The only way to fix this would be to repeatedly sync the
 351                  * ITCs. Until that time we have to avoid ITC.
 352                  */
 353                 clocksource_itc.rating = 50;
 354
 355         paravirt_init_missing_ticks_accounting(smp_processor_id());
 356
 357         /* avoid softlock up message when cpu is unplug and plugged again. */
 358         touch_softlockup_watchdog();
 359
 360         /* Setup the CPU local timer tick */
 361         ia64_cpu_local_tick();
 362
 363         if (!itc_clocksource) {
 364                 /* Sort out mult/shift values: */
 365                 clocksource_itc.mult =
 366                         clocksource_hz2mult(local_cpu_data->itc_freq,
 367                                                 clocksource_itc.shift);
 368                 clocksource_register(&clocksource_itc);
 369                 itc_clocksource = &clocksource_itc;
 370         }
 371 }
 372
 373 static cycle_t itc_get_cycles(void)
 374 {
 375         u64 lcycle, now, ret;
 376
 377         if (!itc_jitter_data.itc_jitter)
 378                 return get_cycles();
 379
 380         lcycle = itc_jitter_data.itc_lastcycle;
 381         now = get_cycles();
 382         if (lcycle && time_after(lcycle, now))
 383                 return lcycle;
 384
 385         /*
 386          * Keep track of the last timer value returned.
 387          * In an SMP environment, you could lose out in contention of
 388          * cmpxchg. If so, your cmpxchg returns new value which the
 389          * winner of contention updated to. Use the new value instead.
 390          */
 391         ret = cmpxchg(&itc_jitter_data.itc_lastcycle, lcycle, now);
 392         if (unlikely(ret != lcycle))
 393                 return ret;
 394
 395         return now;
 396 }
 397
 398
 399 static struct irqaction timer_irqaction = {
 400         .handler =      timer_interrupt,
 401         .flags =        IRQF_DISABLED | IRQF_IRQPOLL,
 402         .name =         "timer"
 403 };
 404
 405 void __init
 406 time_init (void)
 407 {
 408         register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
 409         efi_gettimeofday(&xtime);
 410         ia64_init_itm();
 411
 412         /*
 413          * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
 414          * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
 415          */
 416         set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
 417 }
 418
 419 /*
 420  * Generic udelay assumes that if preemption is allowed and the thread
 421  * migrates to another CPU, that the ITC values are synchronized across
 422  * all CPUs.
 423  */
 424 static void
 425 ia64_itc_udelay (unsigned long usecs)
 426 {
 427         unsigned long start = ia64_get_itc();
 428         unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
 429
 430         while (time_before(ia64_get_itc(), end))
 431                 cpu_relax();
 432 }
 433
 434 void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
 435
 436 void
 437 udelay (unsigned long usecs)
 438 {
 439         (*ia64_udelay)(usecs);
 440 }
 441 EXPORT_SYMBOL(udelay);
 442
 443 /* IA64 doesn't cache the timezone */
 444 void update_vsyscall_tz(void)
 445 {
 446 }
 447
 448 void update_vsyscall(struct timespec *wall, struct clocksource *c)
 449 {
 450         unsigned long flags;
 451
 452         write_seqlock_irqsave(&fsyscall_gtod_data.lock, flags);
 453
 454         /* copy fsyscall clock data */
 455         fsyscall_gtod_data.clk_mask = c->mask;
 456         fsyscall_gtod_data.clk_mult = c->mult;
 457         fsyscall_gtod_data.clk_shift = c->shift;
 458         fsyscall_gtod_data.clk_fsys_mmio = c->fsys_mmio;
 459         fsyscall_gtod_data.clk_cycle_last = c->cycle_last;
 460
 461         /* copy kernel time structures */
 462         fsyscall_gtod_data.wall_time.tv_sec = wall->tv_sec;
 463         fsyscall_gtod_data.wall_time.tv_nsec = wall->tv_nsec;
 464         fsyscall_gtod_data.monotonic_time.tv_sec = wall_to_monotonic.tv_sec
 465                                                         + wall->tv_sec;
 466         fsyscall_gtod_data.monotonic_time.tv_nsec = wall_to_monotonic.tv_nsec
 467                                                         + wall->tv_nsec;
 468
 469         /* normalize */
 470         while (fsyscall_gtod_data.monotonic_time.tv_nsec >= NSEC_PER_SEC) {
 471                 fsyscall_gtod_data.monotonic_time.tv_nsec -= NSEC_PER_SEC;
 472                 fsyscall_gtod_data.monotonic_time.tv_sec++;
 473         }
 474
 475         write_sequnlock_irqrestore(&fsyscall_gtod_data.lock, flags);
 476 }
 477