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 u64 jiffies_64 = INITIAL_JIFFIES;
  36
  37 EXPORT_SYMBOL(jiffies_64);
  38
  39 #define TIME_KEEPER_ID  0       /* smp_processor_id() of time-keeper */
  40
  41 #ifdef CONFIG_IA64_DEBUG_IRQ
  42
  43 unsigned long last_cli_ip;
  44 EXPORT_SYMBOL(last_cli_ip);
  45
  46 #endif
  47
  48 static struct time_interpolator itc_interpolator = {
  49         .shift = 16,
  50         .mask = 0xffffffffffffffffLL,
  51         .source = TIME_SOURCE_CPU
  52 };
  53
  54 static irqreturn_t
  55 timer_interrupt (int irq, void *dev_id, struct pt_regs *regs)
  56 {
  57         unsigned long new_itm;
  58
  59         if (unlikely(cpu_is_offline(smp_processor_id()))) {
  60                 return IRQ_HANDLED;
  61         }
  62
  63         platform_timer_interrupt(irq, dev_id, regs);
  64
  65         new_itm = local_cpu_data->itm_next;
  66
  67         if (!time_after(ia64_get_itc(), new_itm))
  68                 printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
  69                        ia64_get_itc(), new_itm);
  70
  71         profile_tick(CPU_PROFILING, regs);
  72
  73         while (1) {
  74 #ifdef CONFIG_SMP
  75                 /*
  76                  * For UP, this is done in do_timer().  Weird, but
  77                  * fixing that would require updates to all
  78                  * platforms.
  79                  */
  80                 update_process_times(user_mode(regs));
  81 #endif
  82                 new_itm += local_cpu_data->itm_delta;
  83
  84                 if (smp_processor_id() == TIME_KEEPER_ID) {
  85                         /*
  86                          * Here we are in the timer irq handler. We have irqs locally
  87                          * disabled, but we don't know if the timer_bh is running on
  88                          * another CPU. We need to avoid to SMP race by acquiring the
  89                          * xtime_lock.
  90                          */
  91                         write_seqlock(&xtime_lock);
  92                         do_timer(regs);
  93                         local_cpu_data->itm_next = new_itm;
  94                         write_sequnlock(&xtime_lock);
  95                 } else
  96                         local_cpu_data->itm_next = new_itm;
  97
  98                 if (time_after(new_itm, ia64_get_itc()))
  99                         break;
 100         }
 101
 102         do {
 103                 /*
 104                  * If we're too close to the next clock tick for
 105                  * comfort, we increase the safety margin by
 106                  * intentionally dropping the next tick(s).  We do NOT
 107                  * update itm.next because that would force us to call
 108                  * do_timer() which in turn would let our clock run
 109                  * too fast (with the potentially devastating effect
 110                  * of losing monotony of time).
 111                  */
 112                 while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
 113                         new_itm += local_cpu_data->itm_delta;
 114                 ia64_set_itm(new_itm);
 115                 /* double check, in case we got hit by a (slow) PMI: */
 116         } while (time_after_eq(ia64_get_itc(), new_itm));
 117         return IRQ_HANDLED;
 118 }
 119
 120 /*
 121  * Encapsulate access to the itm structure for SMP.
 122  */
 123 void
 124 ia64_cpu_local_tick (void)
 125 {
 126         int cpu = smp_processor_id();
 127         unsigned long shift = 0, delta;
 128
 129         /* arrange for the cycle counter to generate a timer interrupt: */
 130         ia64_set_itv(IA64_TIMER_VECTOR);
 131
 132         delta = local_cpu_data->itm_delta;
 133         /*
 134          * Stagger the timer tick for each CPU so they don't occur all at (almost) the
 135          * same time:
 136          */
 137         if (cpu) {
 138                 unsigned long hi = 1UL << ia64_fls(cpu);
 139                 shift = (2*(cpu - hi) + 1) * delta/hi/2;
 140         }
 141         local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
 142         ia64_set_itm(local_cpu_data->itm_next);
 143 }
 144
 145 static int nojitter;
 146
 147 static int __init nojitter_setup(char *str)
 148 {
 149         nojitter = 1;
 150         printk("Jitter checking for ITC timers disabled\n");
 151         return 1;
 152 }
 153
 154 __setup("nojitter", nojitter_setup);
 155
 156
 157 void __devinit
 158 ia64_init_itm (void)
 159 {
 160         unsigned long platform_base_freq, itc_freq;
 161         struct pal_freq_ratio itc_ratio, proc_ratio;
 162         long status, platform_base_drift, itc_drift;
 163
 164         /*
 165          * According to SAL v2.6, we need to use a SAL call to determine the platform base
 166          * frequency and then a PAL call to determine the frequency ratio between the ITC
 167          * and the base frequency.
 168          */
 169         status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
 170                                     &platform_base_freq, &platform_base_drift);
 171         if (status != 0) {
 172                 printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
 173         } else {
 174                 status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
 175                 if (status != 0)
 176                         printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
 177         }
 178         if (status != 0) {
 179                 /* invent "random" values */
 180                 printk(KERN_ERR
 181                        "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
 182                 platform_base_freq = 100000000;
 183                 platform_base_drift = -1;       /* no drift info */
 184                 itc_ratio.num = 3;
 185                 itc_ratio.den = 1;
 186         }
 187         if (platform_base_freq < 40000000) {
 188                 printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
 189                        platform_base_freq);
 190                 platform_base_freq = 75000000;
 191                 platform_base_drift = -1;
 192         }
 193         if (!proc_ratio.den)
 194                 proc_ratio.den = 1;     /* avoid division by zero */
 195         if (!itc_ratio.den)
 196                 itc_ratio.den = 1;      /* avoid division by zero */
 197
 198         itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
 199         if (platform_base_drift != -1)
 200                 itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
 201         else
 202                 itc_drift = -1;
 203
 204         local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
 205         printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%lu/%lu, "
 206                "ITC freq=%lu.%03luMHz+/-%ldppm\n", smp_processor_id(),
 207                platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
 208                itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000,
 209                itc_drift);
 210
 211         local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
 212         local_cpu_data->itc_freq = itc_freq;
 213         local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
 214         local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
 215                                         + itc_freq/2)/itc_freq;
 216
 217         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
 218                 itc_interpolator.frequency = local_cpu_data->itc_freq;
 219                 itc_interpolator.drift = itc_drift;
 220 #ifdef CONFIG_SMP
 221                 /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
 222                  * Jitter compensation requires a cmpxchg which may limit
 223                  * the scalability of the syscalls for retrieving time.
 224                  * The ITC synchronization is usually successful to within a few
 225                  * ITC ticks but this is not a sure thing. If you need to improve
 226                  * timer performance in SMP situations then boot the kernel with the
 227                  * "nojitter" option. However, doing so may result in time fluctuating (maybe
 228                  * even going backward) if the ITC offsets between the individual CPUs
 229                  * are too large.
 230                  */
 231                 if (!nojitter) itc_interpolator.jitter = 1;
 232 #endif
 233                 register_time_interpolator(&itc_interpolator);
 234         }
 235
 236         /* Setup the CPU local timer tick */
 237         ia64_cpu_local_tick();
 238 }
 239
 240 static struct irqaction timer_irqaction = {
 241         .handler =      timer_interrupt,
 242         .flags =        SA_INTERRUPT,
 243         .name =         "timer"
 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 }