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 */
36 static unsigned long halftick __read_mostly;
39 extern void smp_do_timer(struct pt_regs *regs);
42 irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
45 unsigned long next_tick;
46 unsigned long cycles_elapsed;
47 unsigned long cycles_remainder;
48 unsigned long ticks_elapsed = 1; /* at least one elapsed */
49 int cpu = smp_processor_id();
51 profile_tick(CPU_PROFILING, regs);
53 /* Initialize next_tick to the expected tick time. */
54 next_tick = cpu_data[cpu].it_value;
56 /* Get current interval timer.
57 * CR16 reads as 64 bits in CPU wide mode.
58 * CR16 reads as 32 bits in CPU narrow mode.
62 cycles_elapsed = now - next_tick;
64 /* Determine how much time elapsed. */
65 if (now < next_tick) {
66 /* Scenario 2: CR16 wrapped after clock tick.
67 * 1's complement will give us the "elapse cycles".
69 * This "cr16 wrapped" cruft is primarily for 32-bit kernels.
70 * So think "unsigned long is u32" when reading the code.
71 * And yes, of course 64-bit will someday wrap, but only
72 * every 198841 days on a 1GHz machine.
74 cycles_elapsed = ~cycles_elapsed; /* off by one cycle - don't care */
77 ticks_elapsed += cycles_elapsed / clocktick;
78 cycles_remainder = cycles_elapsed % clocktick;
80 /* Can we differentiate between "early CR16" (aka Scenario 1) and
81 * "long delay" (aka Scenario 3)? I don't think so.
83 * We expected timer_interrupt to be delivered at least a few hundred
84 * cycles after the IT fires. But it's arbitrary how much time passes
85 * before we call it "late". I've picked one second.
87 if (ticks_elapsed > HZ) {
88 /* Scenario 3: very long delay? bad in any case */
89 printk (KERN_CRIT "timer_interrupt(CPU %d): delayed! run ntpdate"
90 " ticks %ld cycles %lX rem %lX"
91 " next/now %lX/%lX\n",
93 ticks_elapsed, cycles_elapsed, cycles_remainder,
96 ticks_elapsed = 1; /* hack to limit damage in loop below */
100 /* Determine when (in CR16 cycles) next IT interrupt will fire.
101 * We want IT to fire modulo clocktick even if we miss/skip some.
102 * But those interrupts don't in fact get delivered that regularly.
104 next_tick = now + (clocktick - cycles_remainder);
106 /* Program the IT when to deliver the next interrupt. */
107 /* Only bottom 32-bits of next_tick are written to cr16. */
108 mtctl(next_tick, 16);
109 cpu_data[cpu].it_value = next_tick;
111 /* Now that we are done mucking with unreliable delivery of interrupts,
112 * go do system house keeping.
114 while (ticks_elapsed--) {
118 update_process_times(user_mode(regs));
121 write_seqlock(&xtime_lock);
123 write_sequnlock(&xtime_lock);
127 /* check soft power switch status */
128 if (cpu == 0 && !atomic_read(&power_tasklet.count))
129 tasklet_schedule(&power_tasklet);
135 unsigned long profile_pc(struct pt_regs *regs)
137 unsigned long pc = instruction_pointer(regs);
139 if (regs->gr[0] & PSW_N)
143 if (in_lock_functions(pc))
149 EXPORT_SYMBOL(profile_pc);
152 /*** converted from ia64 ***/
154 * Return the number of micro-seconds that elapsed since the last
155 * update to wall time (aka xtime). The xtime_lock
156 * must be at least read-locked when calling this routine.
158 static inline unsigned long
163 * FIXME: This won't work on smp because jiffies are updated by cpu 0.
164 * Once parisc-linux learns the cr16 difference between processors,
165 * this could be made to work.
168 unsigned long prev_tick;
169 unsigned long next_tick;
170 unsigned long elapsed_cycles;
173 next_tick = cpu_data[smp_processor_id()].it_value;
174 now = mfctl(16); /* Read the hardware interval timer. */
176 prev_tick = next_tick - clocktick;
178 /* Assume Scenario 1: "now" is later than prev_tick. */
179 elapsed_cycles = now - prev_tick;
181 if (now < prev_tick) {
182 /* Scenario 2: CR16 wrapped!
183 * 1's complement is close enough.
185 elapsed_cycles = ~elapsed_cycles;
188 if (elapsed_cycles > (HZ * clocktick)) {
189 /* Scenario 3: clock ticks are missing. */
190 printk (KERN_CRIT "gettimeoffset(CPU %d): missing ticks!"
191 "cycles %lX prev/now/next %lX/%lX/%lX clock %lX\n",
193 elapsed_cycles, prev_tick, now, next_tick, clocktick);
196 /* FIXME: Can we improve the precision? Not with PAGE0. */
197 usec = (elapsed_cycles * 10000) / PAGE0->mem_10msec;
199 /* add in "lost" jiffies */
200 usec += clocktick * (jiffies - wall_jiffies);
208 do_gettimeofday (struct timeval *tv)
210 unsigned long flags, seq, usec, sec;
212 /* Hold xtime_lock and adjust timeval. */
214 seq = read_seqbegin_irqsave(&xtime_lock, flags);
215 usec = gettimeoffset();
217 usec += (xtime.tv_nsec / 1000);
218 } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
220 /* Move adjusted usec's into sec's. */
221 while (usec >= USEC_PER_SEC) {
222 usec -= USEC_PER_SEC;
226 /* Return adjusted result. */
231 EXPORT_SYMBOL(do_gettimeofday);
234 do_settimeofday (struct timespec *tv)
236 time_t wtm_sec, sec = tv->tv_sec;
237 long wtm_nsec, nsec = tv->tv_nsec;
239 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
242 write_seqlock_irq(&xtime_lock);
245 * This is revolting. We need to set "xtime"
246 * correctly. However, the value in this location is
247 * the value at the most recent update of wall time.
248 * Discover what correction gettimeofday would have
249 * done, and then undo it!
251 nsec -= gettimeoffset() * 1000;
253 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
254 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
256 set_normalized_timespec(&xtime, sec, nsec);
257 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
261 write_sequnlock_irq(&xtime_lock);
265 EXPORT_SYMBOL(do_settimeofday);
268 * XXX: We can do better than this.
269 * Returns nanoseconds
272 unsigned long long sched_clock(void)
274 return (unsigned long long)jiffies * (1000000000 / HZ);
278 void __init start_cpu_itimer(void)
280 unsigned int cpu = smp_processor_id();
281 unsigned long next_tick = mfctl(16) + clocktick;
283 mtctl(next_tick, 16); /* kick off Interval Timer (CR16) */
285 cpu_data[cpu].it_value = next_tick;
288 void __init time_init(void)
290 static struct pdc_tod tod_data;
292 clocktick = (100 * PAGE0->mem_10msec) / HZ;
293 halftick = clocktick / 2;
295 start_cpu_itimer(); /* get CPU 0 started */
297 if(pdc_tod_read(&tod_data) == 0) {
298 write_seqlock_irq(&xtime_lock);
299 xtime.tv_sec = tod_data.tod_sec;
300 xtime.tv_nsec = tod_data.tod_usec * 1000;
301 set_normalized_timespec(&wall_to_monotonic,
302 -xtime.tv_sec, -xtime.tv_nsec);
303 write_sequnlock_irq(&xtime_lock);
305 printk(KERN_ERR "Error reading tod clock\n");