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
  23 #include <asm/machvec.h>
  24 #include <asm/delay.h>
  25 #include <asm/hw_irq.h>
  26 #include <asm/ptrace.h>
  27 #include <asm/sal.h>
  28 #include <asm/sections.h>
  29 #include <asm/system.h>
  30
  31 volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
  32
  33 #ifdef CONFIG_IA64_DEBUG_IRQ
  34
  35 unsigned long last_cli_ip;
  36 EXPORT_SYMBOL(last_cli_ip);
  37
  38 #endif
  39
  40 static struct time_interpolator itc_interpolator = {
  41         .shift = 16,
  42         .mask = 0xffffffffffffffffLL,
  43         .source = TIME_SOURCE_CPU
  44 };
  45
  46 static irqreturn_t
  47 timer_interrupt (int irq, void *dev_id)
  48 {
  49         unsigned long new_itm;
  50
  51         if (unlikely(cpu_is_offline(smp_processor_id()))) {
  52                 return IRQ_HANDLED;
  53         }
  54
  55         platform_timer_interrupt(irq, dev_id);
  56
  57         new_itm = local_cpu_data->itm_next;
  58
  59         if (!time_after(ia64_get_itc(), new_itm))
  60                 printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
  61                        ia64_get_itc(), new_itm);
  62
  63         profile_tick(CPU_PROFILING);
  64
  65         while (1) {
  66                 update_process_times(user_mode(get_irq_regs()));
  67
  68                 new_itm += local_cpu_data->itm_delta;
  69
  70                 if (smp_processor_id() == time_keeper_id) {
  71                         /*
  72                          * Here we are in the timer irq handler. We have irqs locally
  73                          * disabled, but we don't know if the timer_bh is running on
  74                          * another CPU. We need to avoid to SMP race by acquiring the
  75                          * xtime_lock.
  76                          */
  77                         write_seqlock(&xtime_lock);
  78                         do_timer(1);
  79                         local_cpu_data->itm_next = new_itm;
  80                         write_sequnlock(&xtime_lock);
  81                 } else
  82                         local_cpu_data->itm_next = new_itm;
  83
  84                 if (time_after(new_itm, ia64_get_itc()))
  85                         break;
  86
  87                 /*
  88                  * Allow IPIs to interrupt the timer loop.
  89                  */
  90                 local_irq_enable();
  91                 local_irq_disable();
  92         }
  93
  94         do {
  95                 /*
  96                  * If we're too close to the next clock tick for
  97                  * comfort, we increase the safety margin by
  98                  * intentionally dropping the next tick(s).  We do NOT
  99                  * update itm.next because that would force us to call
 100                  * do_timer() which in turn would let our clock run
 101                  * too fast (with the potentially devastating effect
 102                  * of losing monotony of time).
 103                  */
 104                 while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
 105                         new_itm += local_cpu_data->itm_delta;
 106                 ia64_set_itm(new_itm);
 107                 /* double check, in case we got hit by a (slow) PMI: */
 108         } while (time_after_eq(ia64_get_itc(), new_itm));
 109         return IRQ_HANDLED;
 110 }
 111
 112 /*
 113  * Encapsulate access to the itm structure for SMP.
 114  */
 115 void
 116 ia64_cpu_local_tick (void)
 117 {
 118         int cpu = smp_processor_id();
 119         unsigned long shift = 0, delta;
 120
 121         /* arrange for the cycle counter to generate a timer interrupt: */
 122         ia64_set_itv(IA64_TIMER_VECTOR);
 123
 124         delta = local_cpu_data->itm_delta;
 125         /*
 126          * Stagger the timer tick for each CPU so they don't occur all at (almost) the
 127          * same time:
 128          */
 129         if (cpu) {
 130                 unsigned long hi = 1UL << ia64_fls(cpu);
 131                 shift = (2*(cpu - hi) + 1) * delta/hi/2;
 132         }
 133         local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
 134         ia64_set_itm(local_cpu_data->itm_next);
 135 }
 136
 137 static int nojitter;
 138
 139 static int __init nojitter_setup(char *str)
 140 {
 141         nojitter = 1;
 142         printk("Jitter checking for ITC timers disabled\n");
 143         return 1;
 144 }
 145
 146 __setup("nojitter", nojitter_setup);
 147
 148
 149 void __devinit
 150 ia64_init_itm (void)
 151 {
 152         unsigned long platform_base_freq, itc_freq;
 153         struct pal_freq_ratio itc_ratio, proc_ratio;
 154         long status, platform_base_drift, itc_drift;
 155
 156         /*
 157          * According to SAL v2.6, we need to use a SAL call to determine the platform base
 158          * frequency and then a PAL call to determine the frequency ratio between the ITC
 159          * and the base frequency.
 160          */
 161         status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
 162                                     &platform_base_freq, &platform_base_drift);
 163         if (status != 0) {
 164                 printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
 165         } else {
 166                 status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
 167                 if (status != 0)
 168                         printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
 169         }
 170         if (status != 0) {
 171                 /* invent "random" values */
 172                 printk(KERN_ERR
 173                        "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
 174                 platform_base_freq = 100000000;
 175                 platform_base_drift = -1;       /* no drift info */
 176                 itc_ratio.num = 3;
 177                 itc_ratio.den = 1;
 178         }
 179         if (platform_base_freq < 40000000) {
 180                 printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
 181                        platform_base_freq);
 182                 platform_base_freq = 75000000;
 183                 platform_base_drift = -1;
 184         }
 185         if (!proc_ratio.den)
 186                 proc_ratio.den = 1;     /* avoid division by zero */
 187         if (!itc_ratio.den)
 188                 itc_ratio.den = 1;      /* avoid division by zero */
 189
 190         itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
 191
 192         local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
 193         printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
 194                "ITC freq=%lu.%03luMHz", smp_processor_id(),
 195                platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
 196                itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
 197
 198         if (platform_base_drift != -1) {
 199                 itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
 200                 printk("+/-%ldppm\n", itc_drift);
 201         } else {
 202                 itc_drift = -1;
 203                 printk("\n");
 204         }
 205
 206         local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
 207         local_cpu_data->itc_freq = itc_freq;
 208         local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
 209         local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
 210                                         + itc_freq/2)/itc_freq;
 211
 212         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
 213                 itc_interpolator.frequency = local_cpu_data->itc_freq;
 214                 itc_interpolator.drift = itc_drift;
 215 #ifdef CONFIG_SMP
 216                 /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
 217                  * Jitter compensation requires a cmpxchg which may limit
 218                  * the scalability of the syscalls for retrieving time.
 219                  * The ITC synchronization is usually successful to within a few
 220                  * ITC ticks but this is not a sure thing. If you need to improve
 221                  * timer performance in SMP situations then boot the kernel with the
 222                  * "nojitter" option. However, doing so may result in time fluctuating (maybe
 223                  * even going backward) if the ITC offsets between the individual CPUs
 224                  * are too large.
 225                  */
 226                 if (!nojitter) itc_interpolator.jitter = 1;
 227 #endif
 228                 register_time_interpolator(&itc_interpolator);
 229         }
 230
 231         /* Setup the CPU local timer tick */
 232         ia64_cpu_local_tick();
 233 }
 234
 235 static struct irqaction timer_irqaction = {
 236         .handler =      timer_interrupt,
 237         .flags =        IRQF_DISABLED | IRQF_IRQPOLL,
 238         .name =         "timer"
 239 };
 240
 241 void __devinit ia64_disable_timer(void)
 242 {
 243         ia64_set_itv(1 << 16);
 244 }
 245
 246 void __init
 247 time_init (void)
 248 {
 249         register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
 250         efi_gettimeofday(&xtime);
 251         ia64_init_itm();
 252
 253         /*
 254          * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
 255          * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
 256          */
 257         set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
 258 }
 259
 260 /*
 261  * Generic udelay assumes that if preemption is allowed and the thread
 262  * migrates to another CPU, that the ITC values are synchronized across
 263  * all CPUs.
 264  */
 265 static void
 266 ia64_itc_udelay (unsigned long usecs)
 267 {
 268         unsigned long start = ia64_get_itc();
 269         unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
 270
 271         while (time_before(ia64_get_itc(), end))
 272                 cpu_relax();
 273 }
 274
 275 void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
 276
 277 void
 278 udelay (unsigned long usecs)
 279 {
 280         (*ia64_udelay)(usecs);
 281 }
 282 EXPORT_SYMBOL(udelay);
 283
 284 static unsigned long long ia64_itc_printk_clock(void)
 285 {
 286         if (ia64_get_kr(IA64_KR_PER_CPU_DATA))
 287                 return sched_clock();
 288         return 0;
 289 }
 290
 291 static unsigned long long ia64_default_printk_clock(void)
 292 {
 293         return (unsigned long long)(jiffies_64 - INITIAL_JIFFIES) *
 294                 (1000000000/HZ);
 295 }
 296
 297 unsigned long long (*ia64_printk_clock)(void) = &ia64_default_printk_clock;
 298
 299 unsigned long long printk_clock(void)
 300 {
 301         return ia64_printk_clock();
 302 }
 303
 304 void __init
 305 ia64_setup_printk_clock(void)
 306 {
 307         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT))
 308                 ia64_printk_clock = ia64_itc_printk_clock;
 309 }