/* * linux/arch/parisc/kernel/time.c * * Copyright (C) 1991, 1992, 1995 Linus Torvalds * Modifications for ARM (C) 1994, 1995, 1996,1997 Russell King * Copyright (C) 1999 SuSE GmbH, (Philipp Rumpf, prumpf@tux.org) * * 1994-07-02 Alan Modra * fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime * 1998-12-20 Updated NTP code according to technical memorandum Jan '96 * "A Kernel Model for Precision Timekeeping" by Dave Mills */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static unsigned long clocktick __read_mostly; /* timer cycles per tick */ #ifdef CONFIG_SMP extern void smp_do_timer(struct pt_regs *regs); #endif irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs) { unsigned long now; unsigned long next_tick; unsigned long cycles_elapsed; unsigned long cycles_remainder; unsigned int cpu = smp_processor_id(); /* gcc can optimize for "read-only" case with a local clocktick */ unsigned long cpt = clocktick; profile_tick(CPU_PROFILING, regs); /* Initialize next_tick to the expected tick time. */ next_tick = cpu_data[cpu].it_value; /* Get current interval timer. * CR16 reads as 64 bits in CPU wide mode. * CR16 reads as 32 bits in CPU narrow mode. */ now = mfctl(16); cycles_elapsed = now - next_tick; if ((cycles_elapsed >> 5) < cpt) { /* use "cheap" math (add/subtract) instead * of the more expensive div/mul method */ cycles_remainder = cycles_elapsed; while (cycles_remainder > cpt) { cycles_remainder -= cpt; } } else { cycles_remainder = cycles_elapsed % cpt; } /* Can we differentiate between "early CR16" (aka Scenario 1) and * "long delay" (aka Scenario 3)? I don't think so. * * We expected timer_interrupt to be delivered at least a few hundred * cycles after the IT fires. But it's arbitrary how much time passes * before we call it "late". I've picked one second. */ /* aproximate HZ with shifts. Intended math is "(elapsed/clocktick) > HZ" */ #if HZ == 1000 if (cycles_elapsed > (cpt << 10) ) #elif HZ == 250 if (cycles_elapsed > (cpt << 8) ) #elif HZ == 100 if (cycles_elapsed > (cpt << 7) ) #else #warn WTF is HZ set to anyway? if (cycles_elapsed > (HZ * cpt) ) #endif { /* Scenario 3: very long delay? bad in any case */ printk (KERN_CRIT "timer_interrupt(CPU %d): delayed!" " cycles %lX rem %lX " " next/now %lX/%lX\n", cpu, cycles_elapsed, cycles_remainder, next_tick, now ); } /* convert from "division remainder" to "remainder of clock tick" */ cycles_remainder = cpt - cycles_remainder; /* Determine when (in CR16 cycles) next IT interrupt will fire. * We want IT to fire modulo clocktick even if we miss/skip some. * But those interrupts don't in fact get delivered that regularly. */ next_tick = now + cycles_remainder; cpu_data[cpu].it_value = next_tick; /* Skip one clocktick on purpose if we are likely to miss next_tick. * We want to avoid the new next_tick being less than CR16. * If that happened, itimer wouldn't fire until CR16 wrapped. * We'll catch the tick we missed on the tick after that. */ if (!(cycles_remainder >> 13)) next_tick += cpt; /* Program the IT when to deliver the next interrupt. */ /* Only bottom 32-bits of next_tick are written to cr16. */ mtctl(next_tick, 16); /* Done mucking with unreliable delivery of interrupts. * Go do system house keeping. */ #ifdef CONFIG_SMP smp_do_timer(regs); #else update_process_times(user_mode(regs)); #endif if (cpu == 0) { write_seqlock(&xtime_lock); do_timer(regs); write_sequnlock(&xtime_lock); } /* check soft power switch status */ if (cpu == 0 && !atomic_read(&power_tasklet.count)) tasklet_schedule(&power_tasklet); return IRQ_HANDLED; } unsigned long profile_pc(struct pt_regs *regs) { unsigned long pc = instruction_pointer(regs); if (regs->gr[0] & PSW_N) pc -= 4; #ifdef CONFIG_SMP if (in_lock_functions(pc)) pc = regs->gr[2]; #endif return pc; } EXPORT_SYMBOL(profile_pc); /* * Return the number of micro-seconds that elapsed since the last * update to wall time (aka xtime). The xtime_lock * must be at least read-locked when calling this routine. */ static inline unsigned long gettimeoffset (void) { #ifndef CONFIG_SMP /* * FIXME: This won't work on smp because jiffies are updated by cpu 0. * Once parisc-linux learns the cr16 difference between processors, * this could be made to work. */ unsigned long now; unsigned long prev_tick; unsigned long next_tick; unsigned long elapsed_cycles; unsigned long usec; unsigned long cpuid = smp_processor_id(); unsigned long cpt = clocktick; next_tick = cpu_data[cpuid].it_value; now = mfctl(16); /* Read the hardware interval timer. */ prev_tick = next_tick - cpt; /* Assume Scenario 1: "now" is later than prev_tick. */ elapsed_cycles = now - prev_tick; /* aproximate HZ with shifts. Intended math is "(elapsed/clocktick) > HZ" */ #if HZ == 1000 if (elapsed_cycles > (cpt << 10) ) #elif HZ == 250 if (elapsed_cycles > (cpt << 8) ) #elif HZ == 100 if (elapsed_cycles > (cpt << 7) ) #else #warn WTF is HZ set to anyway? if (elapsed_cycles > (HZ * cpt) ) #endif { /* Scenario 3: clock ticks are missing. */ printk (KERN_CRIT "gettimeoffset(CPU %ld): missing %ld ticks!" " cycles %lX prev/now/next %lX/%lX/%lX clock %lX\n", cpuid, elapsed_cycles / cpt, elapsed_cycles, prev_tick, now, next_tick, cpt); } /* FIXME: Can we improve the precision? Not with PAGE0. */ usec = (elapsed_cycles * 10000) / PAGE0->mem_10msec; /* add in "lost" jiffies */ usec += cpt * (jiffies - wall_jiffies); return usec; #else return 0; #endif } void do_gettimeofday (struct timeval *tv) { unsigned long flags, seq, usec, sec; /* Hold xtime_lock and adjust timeval. */ do { seq = read_seqbegin_irqsave(&xtime_lock, flags); usec = gettimeoffset(); sec = xtime.tv_sec; usec += (xtime.tv_nsec / 1000); } while (read_seqretry_irqrestore(&xtime_lock, seq, flags)); /* Move adjusted usec's into sec's. */ while (usec >= USEC_PER_SEC) { usec -= USEC_PER_SEC; ++sec; } /* Return adjusted result. */ tv->tv_sec = sec; tv->tv_usec = usec; } EXPORT_SYMBOL(do_gettimeofday); int do_settimeofday (struct timespec *tv) { time_t wtm_sec, sec = tv->tv_sec; long wtm_nsec, nsec = tv->tv_nsec; if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) return -EINVAL; write_seqlock_irq(&xtime_lock); { /* * This is revolting. We need to set "xtime" * correctly. However, the value in this location is * the value at the most recent update of wall time. * Discover what correction gettimeofday would have * done, and then undo it! */ nsec -= gettimeoffset() * 1000; wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec); wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec); set_normalized_timespec(&xtime, sec, nsec); set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec); ntp_clear(); } write_sequnlock_irq(&xtime_lock); clock_was_set(); return 0; } EXPORT_SYMBOL(do_settimeofday); /* * XXX: We can do better than this. * Returns nanoseconds */ unsigned long long sched_clock(void) { return (unsigned long long)jiffies * (1000000000 / HZ); } void __init start_cpu_itimer(void) { unsigned int cpu = smp_processor_id(); unsigned long next_tick = mfctl(16) + clocktick; mtctl(next_tick, 16); /* kick off Interval Timer (CR16) */ cpu_data[cpu].it_value = next_tick; } void __init time_init(void) { static struct pdc_tod tod_data; clocktick = (100 * PAGE0->mem_10msec) / HZ; start_cpu_itimer(); /* get CPU 0 started */ if(pdc_tod_read(&tod_data) == 0) { write_seqlock_irq(&xtime_lock); xtime.tv_sec = tod_data.tod_sec; xtime.tv_nsec = tod_data.tod_usec * 1000; set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec); write_sequnlock_irq(&xtime_lock); } else { printk(KERN_ERR "Error reading tod clock\n"); xtime.tv_sec = 0; xtime.tv_nsec = 0; } }