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