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 volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
  33
  34 #ifdef CONFIG_IA64_DEBUG_IRQ
  35
  36 unsigned long last_cli_ip;
  37 EXPORT_SYMBOL(last_cli_ip);
  38
  39 #endif
  40
  41 static struct time_interpolator itc_interpolator = {
  42         .shift = 16,
  43         .mask = 0xffffffffffffffffLL,
  44         .source = TIME_SOURCE_CPU
  45 };
  46
  47 static irqreturn_t
  48 timer_interrupt (int irq, void *dev_id)
  49 {
  50         unsigned long new_itm;
  51
  52         if (unlikely(cpu_is_offline(smp_processor_id()))) {
  53                 return IRQ_HANDLED;
  54         }
  55
  56         platform_timer_interrupt(irq, dev_id);
  57
  58         new_itm = local_cpu_data->itm_next;
  59
  60         if (!time_after(ia64_get_itc(), new_itm))
  61                 printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
  62                        ia64_get_itc(), new_itm);
  63
  64         profile_tick(CPU_PROFILING);
  65
  66         while (1) {
  67                 update_process_times(user_mode(get_irq_regs()));
  68
  69                 new_itm += local_cpu_data->itm_delta;
  70
  71                 if (smp_processor_id() == time_keeper_id) {
  72                         /*
  73                          * Here we are in the timer irq handler. We have irqs locally
  74                          * disabled, but we don't know if the timer_bh is running on
  75                          * another CPU. We need to avoid to SMP race by acquiring the
  76                          * xtime_lock.
  77                          */
  78                         write_seqlock(&xtime_lock);
  79                         do_timer(1);
  80                         local_cpu_data->itm_next = new_itm;
  81                         write_sequnlock(&xtime_lock);
  82                 } else
  83                         local_cpu_data->itm_next = new_itm;
  84
  85                 if (time_after(new_itm, ia64_get_itc()))
  86                         break;
  87
  88                 /*
  89                  * Allow IPIs to interrupt the timer loop.
  90                  */
  91                 local_irq_enable();
  92                 local_irq_disable();
  93         }
  94
  95         do {
  96                 /*
  97                  * If we're too close to the next clock tick for
  98                  * comfort, we increase the safety margin by
  99                  * intentionally dropping the next tick(s).  We do NOT
 100                  * update itm.next because that would force us to call
 101                  * do_timer() which in turn would let our clock run
 102                  * too fast (with the potentially devastating effect
 103                  * of losing monotony of time).
 104                  */
 105                 while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
 106                         new_itm += local_cpu_data->itm_delta;
 107                 ia64_set_itm(new_itm);
 108                 /* double check, in case we got hit by a (slow) PMI: */
 109         } while (time_after_eq(ia64_get_itc(), new_itm));
 110         return IRQ_HANDLED;
 111 }
 112
 113 /*
 114  * Encapsulate access to the itm structure for SMP.
 115  */
 116 void
 117 ia64_cpu_local_tick (void)
 118 {
 119         int cpu = smp_processor_id();
 120         unsigned long shift = 0, delta;
 121
 122         /* arrange for the cycle counter to generate a timer interrupt: */
 123         ia64_set_itv(IA64_TIMER_VECTOR);
 124
 125         delta = local_cpu_data->itm_delta;
 126         /*
 127          * Stagger the timer tick for each CPU so they don't occur all at (almost) the
 128          * same time:
 129          */
 130         if (cpu) {
 131                 unsigned long hi = 1UL << ia64_fls(cpu);
 132                 shift = (2*(cpu - hi) + 1) * delta/hi/2;
 133         }
 134         local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
 135         ia64_set_itm(local_cpu_data->itm_next);
 136 }
 137
 138 static int nojitter;
 139
 140 static int __init nojitter_setup(char *str)
 141 {
 142         nojitter = 1;
 143         printk("Jitter checking for ITC timers disabled\n");
 144         return 1;
 145 }
 146
 147 __setup("nojitter", nojitter_setup);
 148
 149
 150 void __devinit
 151 ia64_init_itm (void)
 152 {
 153         unsigned long platform_base_freq, itc_freq;
 154         struct pal_freq_ratio itc_ratio, proc_ratio;
 155         long status, platform_base_drift, itc_drift;
 156
 157         /*
 158          * According to SAL v2.6, we need to use a SAL call to determine the platform base
 159          * frequency and then a PAL call to determine the frequency ratio between the ITC
 160          * and the base frequency.
 161          */
 162         status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
 163                                     &platform_base_freq, &platform_base_drift);
 164         if (status != 0) {
 165                 printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
 166         } else {
 167                 status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
 168                 if (status != 0)
 169                         printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
 170         }
 171         if (status != 0) {
 172                 /* invent "random" values */
 173                 printk(KERN_ERR
 174                        "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
 175                 platform_base_freq = 100000000;
 176                 platform_base_drift = -1;       /* no drift info */
 177                 itc_ratio.num = 3;
 178                 itc_ratio.den = 1;
 179         }
 180         if (platform_base_freq < 40000000) {
 181                 printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
 182                        platform_base_freq);
 183                 platform_base_freq = 75000000;
 184                 platform_base_drift = -1;
 185         }
 186         if (!proc_ratio.den)
 187                 proc_ratio.den = 1;     /* avoid division by zero */
 188         if (!itc_ratio.den)
 189                 itc_ratio.den = 1;      /* avoid division by zero */
 190
 191         itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
 192
 193         local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
 194         printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
 195                "ITC freq=%lu.%03luMHz", smp_processor_id(),
 196                platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
 197                itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
 198
 199         if (platform_base_drift != -1) {
 200                 itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
 201                 printk("+/-%ldppm\n", itc_drift);
 202         } else {
 203                 itc_drift = -1;
 204                 printk("\n");
 205         }
 206
 207         local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
 208         local_cpu_data->itc_freq = itc_freq;
 209         local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
 210         local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
 211                                         + itc_freq/2)/itc_freq;
 212
 213         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
 214                 itc_interpolator.frequency = local_cpu_data->itc_freq;
 215                 itc_interpolator.drift = itc_drift;
 216 #ifdef CONFIG_SMP
 217                 /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
 218                  * Jitter compensation requires a cmpxchg which may limit
 219                  * the scalability of the syscalls for retrieving time.
 220                  * The ITC synchronization is usually successful to within a few
 221                  * ITC ticks but this is not a sure thing. If you need to improve
 222                  * timer performance in SMP situations then boot the kernel with the
 223                  * "nojitter" option. However, doing so may result in time fluctuating (maybe
 224                  * even going backward) if the ITC offsets between the individual CPUs
 225                  * are too large.
 226                  */
 227                 if (!nojitter) itc_interpolator.jitter = 1;
 228 #endif
 229                 register_time_interpolator(&itc_interpolator);
 230         }
 231
 232         /* Setup the CPU local timer tick */
 233         ia64_cpu_local_tick();
 234 }
 235
 236 static struct irqaction timer_irqaction = {
 237         .handler =      timer_interrupt,
 238         .flags =        IRQF_DISABLED | IRQF_IRQPOLL,
 239         .name =         "timer"
 240 };
 241
 242 void __devinit ia64_disable_timer(void)
 243 {
 244         ia64_set_itv(1 << 16);
 245 }
 246
 247 void __init
 248 time_init (void)
 249 {
 250         register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
 251         efi_gettimeofday(&xtime);
 252         ia64_init_itm();
 253
 254         /*
 255          * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
 256          * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
 257          */
 258         set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
 259 }
 260
 261 /*
 262  * Generic udelay assumes that if preemption is allowed and the thread
 263  * migrates to another CPU, that the ITC values are synchronized across
 264  * all CPUs.
 265  */
 266 static void
 267 ia64_itc_udelay (unsigned long usecs)
 268 {
 269         unsigned long start = ia64_get_itc();
 270         unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
 271
 272         while (time_before(ia64_get_itc(), end))
 273                 cpu_relax();
 274 }
 275
 276 void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
 277
 278 void
 279 udelay (unsigned long usecs)
 280 {
 281         (*ia64_udelay)(usecs);
 282 }
 283 EXPORT_SYMBOL(udelay);
 284
 285 static unsigned long long ia64_itc_printk_clock(void)
 286 {
 287         if (ia64_get_kr(IA64_KR_PER_CPU_DATA))
 288                 return sched_clock();
 289         return 0;
 290 }
 291
 292 static unsigned long long ia64_default_printk_clock(void)
 293 {
 294         return (unsigned long long)(jiffies_64 - INITIAL_JIFFIES) *
 295                 (1000000000/HZ);
 296 }
 297
 298 unsigned long long (*ia64_printk_clock)(void) = &ia64_default_printk_clock;
 299
 300 unsigned long long printk_clock(void)
 301 {
 302         return ia64_printk_clock();
 303 }
 304
 305 void __init
 306 ia64_setup_printk_clock(void)
 307 {
 308         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT))
 309                 ia64_printk_clock = ia64_itc_printk_clock;
 310 }