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 long ticks_elapsed = 1; /* at least one elapsed */
48 int cpu = smp_processor_id();
50 /* gcc can optimize for "read-only" case with a local clocktick */
51 unsigned long local_ct = clocktick;
53 profile_tick(CPU_PROFILING, regs);
55 /* Initialize next_tick to the expected tick time. */
56 next_tick = cpu_data[cpu].it_value;
58 /* Get current interval timer.
59 * CR16 reads as 64 bits in CPU wide mode.
60 * CR16 reads as 32 bits in CPU narrow mode.
64 cycles_elapsed = now - next_tick;
66 /* Determine how much time elapsed. */
67 if (now < next_tick) {
68 /* Scenario 2: CR16 wrapped after clock tick.
69 * 1's complement will give us the "elapse cycles".
71 * This "cr16 wrapped" cruft is primarily for 32-bit kernels.
72 * So think "unsigned long is u32" when reading the code.
73 * And yes, of course 64-bit will someday wrap, but only
74 * every 198841 days on a 1GHz machine.
76 cycles_elapsed = ~cycles_elapsed; /* off by one cycle - don't care */
79 if (likely(cycles_elapsed < local_ct)) {
80 /* ticks_elapsed = 1 -- We already assumed one tick elapsed. */
81 cycles_remainder = cycles_elapsed;
83 /* more than one tick elapsed. Do "expensive" math. */
84 ticks_elapsed += cycles_elapsed / local_ct;
86 /* Faster version of "remainder = elapsed % clocktick" */
87 cycles_remainder = cycles_elapsed - (ticks_elapsed * local_ct);
90 /* Can we differentiate between "early CR16" (aka Scenario 1) and
91 * "long delay" (aka Scenario 3)? I don't think so.
93 * We expected timer_interrupt to be delivered at least a few hundred
94 * cycles after the IT fires. But it's arbitrary how much time passes
95 * before we call it "late". I've picked one second.
97 if (ticks_elapsed > HZ) {
98 /* Scenario 3: very long delay? bad in any case */
99 printk (KERN_CRIT "timer_interrupt(CPU %d): delayed!"
100 " ticks %ld cycles %lX rem %lX"
101 " next/now %lX/%lX\n",
103 ticks_elapsed, cycles_elapsed, 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 + (local_ct - cycles_remainder);
114 /* Skip one clocktick on purpose if we are likely to miss next_tick.
115 * We'll catch what we missed on the tick after that.
116 * We should never need 0x1000 cycles to read CR16, calc the
117 * new next_tick, then write CR16 back. */
118 if (!((local_ct - cycles_remainder) >> 12))
119 next_tick += local_ct;
121 /* Program the IT when to deliver the next interrupt. */
122 /* Only bottom 32-bits of next_tick are written to cr16. */
123 cpu_data[cpu].it_value = next_tick;
124 mtctl(next_tick, 16);
126 /* Now that we are done mucking with unreliable delivery of interrupts,
127 * go do system house keeping.
129 while (ticks_elapsed--) {
133 update_process_times(user_mode(regs));
136 write_seqlock(&xtime_lock);
138 write_sequnlock(&xtime_lock);
142 /* check soft power switch status */
143 if (cpu == 0 && !atomic_read(&power_tasklet.count))
144 tasklet_schedule(&power_tasklet);
150 unsigned long profile_pc(struct pt_regs *regs)
152 unsigned long pc = instruction_pointer(regs);
154 if (regs->gr[0] & PSW_N)
158 if (in_lock_functions(pc))
164 EXPORT_SYMBOL(profile_pc);
167 /*** converted from ia64 ***/
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
178 * FIXME: This won't work on smp because jiffies are updated by cpu 0.
179 * Once parisc-linux learns the cr16 difference between processors,
180 * this could be made to work.
183 unsigned long prev_tick;
184 unsigned long next_tick;
185 unsigned long elapsed_cycles;
187 unsigned long cpuid = smp_processor_id();
188 unsigned long local_ct = clocktick;
190 next_tick = cpu_data[cpuid].it_value;
191 now = mfctl(16); /* Read the hardware interval timer. */
193 prev_tick = next_tick - local_ct;
195 /* Assume Scenario 1: "now" is later than prev_tick. */
196 elapsed_cycles = now - prev_tick;
198 if (now < prev_tick) {
199 /* Scenario 2: CR16 wrapped!
200 * ones complement is off-by-one. Don't care.
202 elapsed_cycles = ~elapsed_cycles;
205 if (elapsed_cycles > (HZ * local_ct)) {
206 /* Scenario 3: clock ticks are missing. */
207 printk (KERN_CRIT "gettimeoffset(CPU %d): missing ticks!"
208 "cycles %lX prev/now/next %lX/%lX/%lX clock %lX\n",
210 elapsed_cycles, prev_tick, now, next_tick, local_ct);
213 /* FIXME: Can we improve the precision? Not with PAGE0. */
214 usec = (elapsed_cycles * 10000) / PAGE0->mem_10msec;
216 /* add in "lost" jiffies */
217 usec += local_ct * (jiffies - wall_jiffies);
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");