2 * linux/arch/parisc/kernel/time.c
4 * Copyright (C) 1991, 1992, 1995 Linus Torvalds
5 * Modifications for ARM (C) 1994, 1995, 1996,1997 Russell King
6 * Copyright (C) 1999 SuSE GmbH, (Philipp Rumpf, prumpf@tux.org)
8 * 1994-07-02 Alan Modra
9 * fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
10 * 1998-12-20 Updated NTP code according to technical memorandum Jan '96
11 * "A Kernel Model for Precision Timekeeping" by Dave Mills
13 #include <linux/errno.h>
14 #include <linux/module.h>
15 #include <linux/sched.h>
16 #include <linux/kernel.h>
17 #include <linux/param.h>
18 #include <linux/string.h>
20 #include <linux/interrupt.h>
21 #include <linux/time.h>
22 #include <linux/init.h>
23 #include <linux/smp.h>
24 #include <linux/profile.h>
26 #include <asm/uaccess.h>
29 #include <asm/param.h>
33 #include <linux/timex.h>
35 static unsigned long clocktick __read_mostly; /* timer cycles per tick */
38 extern void smp_do_timer(struct pt_regs *regs);
41 irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
44 unsigned long next_tick;
45 unsigned long cycles_elapsed;
46 unsigned long cycles_remainder;
47 unsigned int cpu = smp_processor_id();
49 /* gcc can optimize for "read-only" case with a local clocktick */
50 unsigned long cpt = clocktick;
52 profile_tick(CPU_PROFILING, regs);
54 /* Initialize next_tick to the expected tick time. */
55 next_tick = cpu_data[cpu].it_value;
57 /* Get current interval timer.
58 * CR16 reads as 64 bits in CPU wide mode.
59 * CR16 reads as 32 bits in CPU narrow mode.
63 cycles_elapsed = now - next_tick;
65 if ((cycles_elapsed >> 5) < cpt) {
66 /* use "cheap" math (add/subtract) instead
67 * of the more expensive div/mul method
69 cycles_remainder = cycles_elapsed;
70 while (cycles_remainder > cpt) {
71 cycles_remainder -= cpt;
74 cycles_remainder = cycles_elapsed % cpt;
77 /* Can we differentiate between "early CR16" (aka Scenario 1) and
78 * "long delay" (aka Scenario 3)? I don't think so.
80 * We expected timer_interrupt to be delivered at least a few hundred
81 * cycles after the IT fires. But it's arbitrary how much time passes
82 * before we call it "late". I've picked one second.
84 /* aproximate HZ with shifts. Intended math is "(elapsed/clocktick) > HZ" */
86 if (cycles_elapsed > (cpt << 10) )
88 if (cycles_elapsed > (cpt << 8) )
90 if (cycles_elapsed > (cpt << 7) )
92 #warn WTF is HZ set to anyway?
93 if (cycles_elapsed > (HZ * cpt) )
96 /* Scenario 3: very long delay? bad in any case */
97 printk (KERN_CRIT "timer_interrupt(CPU %d): delayed!"
98 " cycles %lX rem %lX "
99 " next/now %lX/%lX\n",
101 cycles_elapsed, cycles_remainder,
105 /* convert from "division remainder" to "remainder of clock tick" */
106 cycles_remainder = cpt - cycles_remainder;
108 /* Determine when (in CR16 cycles) next IT interrupt will fire.
109 * We want IT to fire modulo clocktick even if we miss/skip some.
110 * But those interrupts don't in fact get delivered that regularly.
112 next_tick = now + cycles_remainder;
114 cpu_data[cpu].it_value = next_tick;
116 /* Skip one clocktick on purpose if we are likely to miss next_tick.
117 * We want to avoid the new next_tick being less than CR16.
118 * If that happened, itimer wouldn't fire until CR16 wrapped.
119 * We'll catch the tick we missed on the tick after that.
121 if (!(cycles_remainder >> 13))
124 /* Program the IT when to deliver the next interrupt. */
125 /* Only bottom 32-bits of next_tick are written to cr16. */
126 mtctl(next_tick, 16);
129 /* Done mucking with unreliable delivery of interrupts.
130 * Go do system house keeping.
135 update_process_times(user_mode(regs));
138 write_seqlock(&xtime_lock);
140 write_sequnlock(&xtime_lock);
143 /* check soft power switch status */
144 if (cpu == 0 && !atomic_read(&power_tasklet.count))
145 tasklet_schedule(&power_tasklet);
151 unsigned long profile_pc(struct pt_regs *regs)
153 unsigned long pc = instruction_pointer(regs);
155 if (regs->gr[0] & PSW_N)
159 if (in_lock_functions(pc))
165 EXPORT_SYMBOL(profile_pc);
169 * Return the number of micro-seconds that elapsed since the last
170 * update to wall time (aka xtime). The xtime_lock
171 * must be at least read-locked when calling this routine.
173 static inline unsigned long gettimeoffset (void)
177 * FIXME: This won't work on smp because jiffies are updated by cpu 0.
178 * Once parisc-linux learns the cr16 difference between processors,
179 * this could be made to work.
182 unsigned long prev_tick;
183 unsigned long next_tick;
184 unsigned long elapsed_cycles;
186 unsigned long cpuid = smp_processor_id();
187 unsigned long cpt = clocktick;
189 next_tick = cpu_data[cpuid].it_value;
190 now = mfctl(16); /* Read the hardware interval timer. */
192 prev_tick = next_tick - cpt;
194 /* Assume Scenario 1: "now" is later than prev_tick. */
195 elapsed_cycles = now - prev_tick;
197 /* aproximate HZ with shifts. Intended math is "(elapsed/clocktick) > HZ" */
199 if (elapsed_cycles > (cpt << 10) )
201 if (elapsed_cycles > (cpt << 8) )
203 if (elapsed_cycles > (cpt << 7) )
205 #warn WTF is HZ set to anyway?
206 if (elapsed_cycles > (HZ * cpt) )
209 /* Scenario 3: clock ticks are missing. */
210 printk (KERN_CRIT "gettimeoffset(CPU %ld): missing %ld ticks!"
211 " cycles %lX prev/now/next %lX/%lX/%lX clock %lX\n",
212 cpuid, elapsed_cycles / cpt,
213 elapsed_cycles, prev_tick, now, next_tick, cpt);
216 /* FIXME: Can we improve the precision? Not with PAGE0. */
217 usec = (elapsed_cycles * 10000) / PAGE0->mem_10msec;
225 do_gettimeofday (struct timeval *tv)
227 unsigned long flags, seq, usec, sec;
229 /* Hold xtime_lock and adjust timeval. */
231 seq = read_seqbegin_irqsave(&xtime_lock, flags);
232 usec = gettimeoffset();
234 usec += (xtime.tv_nsec / 1000);
235 } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
237 /* Move adjusted usec's into sec's. */
238 while (usec >= USEC_PER_SEC) {
239 usec -= USEC_PER_SEC;
243 /* Return adjusted result. */
248 EXPORT_SYMBOL(do_gettimeofday);
251 do_settimeofday (struct timespec *tv)
253 time_t wtm_sec, sec = tv->tv_sec;
254 long wtm_nsec, nsec = tv->tv_nsec;
256 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
259 write_seqlock_irq(&xtime_lock);
262 * This is revolting. We need to set "xtime"
263 * correctly. However, the value in this location is
264 * the value at the most recent update of wall time.
265 * Discover what correction gettimeofday would have
266 * done, and then undo it!
268 nsec -= gettimeoffset() * 1000;
270 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
271 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
273 set_normalized_timespec(&xtime, sec, nsec);
274 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
278 write_sequnlock_irq(&xtime_lock);
282 EXPORT_SYMBOL(do_settimeofday);
285 * XXX: We can do better than this.
286 * Returns nanoseconds
289 unsigned long long sched_clock(void)
291 return (unsigned long long)jiffies * (1000000000 / HZ);
295 void __init start_cpu_itimer(void)
297 unsigned int cpu = smp_processor_id();
298 unsigned long next_tick = mfctl(16) + clocktick;
300 mtctl(next_tick, 16); /* kick off Interval Timer (CR16) */
302 cpu_data[cpu].it_value = next_tick;
305 void __init time_init(void)
307 static struct pdc_tod tod_data;
309 clocktick = (100 * PAGE0->mem_10msec) / HZ;
311 start_cpu_itimer(); /* get CPU 0 started */
313 if(pdc_tod_read(&tod_data) == 0) {
314 write_seqlock_irq(&xtime_lock);
315 xtime.tv_sec = tod_data.tod_sec;
316 xtime.tv_nsec = tod_data.tod_usec * 1000;
317 set_normalized_timespec(&wall_to_monotonic,
318 -xtime.tv_sec, -xtime.tv_nsec);
319 write_sequnlock_irq(&xtime_lock);
321 printk(KERN_ERR "Error reading tod clock\n");