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 #include <linux/config.h>
  12
  13 #include <linux/cpu.h>
  14 #include <linux/init.h>
  15 #include <linux/kernel.h>
  16 #include <linux/module.h>
  17 #include <linux/profile.h>
  18 #include <linux/sched.h>
  19 #include <linux/time.h>
  20 #include <linux/interrupt.h>
  21 #include <linux/efi.h>
  22 #include <linux/profile.h>
  23 #include <linux/timex.h>
  24
  25 #include <asm/machvec.h>
  26 #include <asm/delay.h>
  27 #include <asm/hw_irq.h>
  28 #include <asm/ptrace.h>
  29 #include <asm/sal.h>
  30 #include <asm/sections.h>
  31 #include <asm/system.h>
  32
  33 extern unsigned long wall_jiffies;
  34
  35 volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
  36
  37 #ifdef CONFIG_IA64_DEBUG_IRQ
  38
  39 unsigned long last_cli_ip;
  40 EXPORT_SYMBOL(last_cli_ip);
  41
  42 #endif
  43
  44 static struct time_interpolator itc_interpolator = {
  45         .shift = 16,
  46         .mask = 0xffffffffffffffffLL,
  47         .source = TIME_SOURCE_CPU
  48 };
  49
  50 static irqreturn_t
  51 timer_interrupt (int irq, void *dev_id, struct pt_regs *regs)
  52 {
  53         unsigned long new_itm;
  54
  55         if (unlikely(cpu_is_offline(smp_processor_id()))) {
  56                 return IRQ_HANDLED;
  57         }
  58
  59         platform_timer_interrupt(irq, dev_id, regs);
  60
  61         new_itm = local_cpu_data->itm_next;
  62
  63         if (!time_after(ia64_get_itc(), new_itm))
  64                 printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
  65                        ia64_get_itc(), new_itm);
  66
  67         profile_tick(CPU_PROFILING, regs);
  68
  69         while (1) {
  70                 update_process_times(user_mode(regs));
  71
  72                 new_itm += local_cpu_data->itm_delta;
  73
  74                 if (smp_processor_id() == time_keeper_id) {
  75                         /*
  76                          * Here we are in the timer irq handler. We have irqs locally
  77                          * disabled, but we don't know if the timer_bh is running on
  78                          * another CPU. We need to avoid to SMP race by acquiring the
  79                          * xtime_lock.
  80                          */
  81                         write_seqlock(&xtime_lock);
  82                         do_timer(regs);
  83                         local_cpu_data->itm_next = new_itm;
  84                         write_sequnlock(&xtime_lock);
  85                 } else
  86                         local_cpu_data->itm_next = new_itm;
  87
  88                 if (time_after(new_itm, ia64_get_itc()))
  89                         break;
  90         }
  91
  92         do {
  93                 /*
  94                  * If we're too close to the next clock tick for
  95                  * comfort, we increase the safety margin by
  96                  * intentionally dropping the next tick(s).  We do NOT
  97                  * update itm.next because that would force us to call
  98                  * do_timer() which in turn would let our clock run
  99                  * too fast (with the potentially devastating effect
 100                  * of losing monotony of time).
 101                  */
 102                 while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
 103                         new_itm += local_cpu_data->itm_delta;
 104                 ia64_set_itm(new_itm);
 105                 /* double check, in case we got hit by a (slow) PMI: */
 106         } while (time_after_eq(ia64_get_itc(), new_itm));
 107         return IRQ_HANDLED;
 108 }
 109
 110 /*
 111  * Encapsulate access to the itm structure for SMP.
 112  */
 113 void
 114 ia64_cpu_local_tick (void)
 115 {
 116         int cpu = smp_processor_id();
 117         unsigned long shift = 0, delta;
 118
 119         /* arrange for the cycle counter to generate a timer interrupt: */
 120         ia64_set_itv(IA64_TIMER_VECTOR);
 121
 122         delta = local_cpu_data->itm_delta;
 123         /*
 124          * Stagger the timer tick for each CPU so they don't occur all at (almost) the
 125          * same time:
 126          */
 127         if (cpu) {
 128                 unsigned long hi = 1UL << ia64_fls(cpu);
 129                 shift = (2*(cpu - hi) + 1) * delta/hi/2;
 130         }
 131         local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
 132         ia64_set_itm(local_cpu_data->itm_next);
 133 }
 134
 135 static int nojitter;
 136
 137 static int __init nojitter_setup(char *str)
 138 {
 139         nojitter = 1;
 140         printk("Jitter checking for ITC timers disabled\n");
 141         return 1;
 142 }
 143
 144 __setup("nojitter", nojitter_setup);
 145
 146
 147 void __devinit
 148 ia64_init_itm (void)
 149 {
 150         unsigned long platform_base_freq, itc_freq;
 151         struct pal_freq_ratio itc_ratio, proc_ratio;
 152         long status, platform_base_drift, itc_drift;
 153
 154         /*
 155          * According to SAL v2.6, we need to use a SAL call to determine the platform base
 156          * frequency and then a PAL call to determine the frequency ratio between the ITC
 157          * and the base frequency.
 158          */
 159         status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
 160                                     &platform_base_freq, &platform_base_drift);
 161         if (status != 0) {
 162                 printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
 163         } else {
 164                 status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
 165                 if (status != 0)
 166                         printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
 167         }
 168         if (status != 0) {
 169                 /* invent "random" values */
 170                 printk(KERN_ERR
 171                        "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
 172                 platform_base_freq = 100000000;
 173                 platform_base_drift = -1;       /* no drift info */
 174                 itc_ratio.num = 3;
 175                 itc_ratio.den = 1;
 176         }
 177         if (platform_base_freq < 40000000) {
 178                 printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
 179                        platform_base_freq);
 180                 platform_base_freq = 75000000;
 181                 platform_base_drift = -1;
 182         }
 183         if (!proc_ratio.den)
 184                 proc_ratio.den = 1;     /* avoid division by zero */
 185         if (!itc_ratio.den)
 186                 itc_ratio.den = 1;      /* avoid division by zero */
 187
 188         itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
 189
 190         local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
 191         printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
 192                "ITC freq=%lu.%03luMHz", smp_processor_id(),
 193                platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
 194                itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
 195
 196         if (platform_base_drift != -1) {
 197                 itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
 198                 printk("+/-%ldppm\n", itc_drift);
 199         } else {
 200                 itc_drift = -1;
 201                 printk("\n");
 202         }
 203
 204         local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
 205         local_cpu_data->itc_freq = itc_freq;
 206         local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
 207         local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
 208                                         + itc_freq/2)/itc_freq;
 209
 210         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
 211                 itc_interpolator.frequency = local_cpu_data->itc_freq;
 212                 itc_interpolator.drift = itc_drift;
 213 #ifdef CONFIG_SMP
 214                 /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
 215                  * Jitter compensation requires a cmpxchg which may limit
 216                  * the scalability of the syscalls for retrieving time.
 217                  * The ITC synchronization is usually successful to within a few
 218                  * ITC ticks but this is not a sure thing. If you need to improve
 219                  * timer performance in SMP situations then boot the kernel with the
 220                  * "nojitter" option. However, doing so may result in time fluctuating (maybe
 221                  * even going backward) if the ITC offsets between the individual CPUs
 222                  * are too large.
 223                  */
 224                 if (!nojitter) itc_interpolator.jitter = 1;
 225 #endif
 226                 register_time_interpolator(&itc_interpolator);
 227         }
 228
 229         /* Setup the CPU local timer tick */
 230         ia64_cpu_local_tick();
 231 }
 232
 233 static struct irqaction timer_irqaction = {
 234         .handler =      timer_interrupt,
 235         .flags =        SA_INTERRUPT,
 236         .name =         "timer"
 237 };
 238
 239 void __devinit ia64_disable_timer(void)
 240 {
 241         ia64_set_itv(1 << 16);
 242 }
 243
 244 void __init
 245 time_init (void)
 246 {
 247         register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
 248         efi_gettimeofday(&xtime);
 249         ia64_init_itm();
 250
 251         /*
 252          * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
 253          * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
 254          */
 255         set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
 256 }
 257
 258 /*
 259  * Generic udelay assumes that if preemption is allowed and the thread
 260  * migrates to another CPU, that the ITC values are synchronized across
 261  * all CPUs.
 262  */
 263 static void
 264 ia64_itc_udelay (unsigned long usecs)
 265 {
 266         unsigned long start = ia64_get_itc();
 267         unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
 268
 269         while (time_before(ia64_get_itc(), end))
 270                 cpu_relax();
 271 }
 272
 273 void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
 274
 275 void
 276 udelay (unsigned long usecs)
 277 {
 278         (*ia64_udelay)(usecs);
 279 }
 280 EXPORT_SYMBOL(udelay);
 281
 282 static unsigned long long ia64_itc_printk_clock(void)
 283 {
 284         if (ia64_get_kr(IA64_KR_PER_CPU_DATA))
 285                 return sched_clock();
 286         return 0;
 287 }
 288
 289 static unsigned long long ia64_default_printk_clock(void)
 290 {
 291         return (unsigned long long)(jiffies_64 - INITIAL_JIFFIES) *
 292                 (1000000000/HZ);
 293 }
 294
 295 unsigned long long (*ia64_printk_clock)(void) = &ia64_default_printk_clock;
 296
 297 unsigned long long printk_clock(void)
 298 {
 299         return ia64_printk_clock();
 300 }
 301
 302 void __init
 303 ia64_setup_printk_clock(void)
 304 {
 305         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT))
 306                 ia64_printk_clock = ia64_itc_printk_clock;
 307 }