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