2 * linux/arch/ia64/kernel/time.c
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>
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/timex.h>
22 #include <linux/clocksource.h>
24 #include <asm/machvec.h>
25 #include <asm/delay.h>
26 #include <asm/hw_irq.h>
27 #include <asm/paravirt.h>
28 #include <asm/ptrace.h>
30 #include <asm/sections.h>
31 #include <asm/system.h>
33 #include "fsyscall_gtod_data.h"
35 static cycle_t
itc_get_cycles(void);
37 struct fsyscall_gtod_data_t fsyscall_gtod_data
= {
38 .lock
= SEQLOCK_UNLOCKED
,
41 struct itc_jitter_data_t itc_jitter_data
;
43 volatile int time_keeper_id
= 0; /* smp_processor_id() of time-keeper */
45 #ifdef CONFIG_IA64_DEBUG_IRQ
47 unsigned long last_cli_ip
;
48 EXPORT_SYMBOL(last_cli_ip
);
52 #ifdef CONFIG_PARAVIRT
54 paravirt_clocksource_resume(void)
56 if (pv_time_ops
.clocksource_resume
)
57 pv_time_ops
.clocksource_resume();
61 static struct clocksource clocksource_itc
= {
64 .read
= itc_get_cycles
,
65 .mask
= CLOCKSOURCE_MASK(64),
66 .mult
= 0, /*to be calculated*/
68 .flags
= CLOCK_SOURCE_IS_CONTINUOUS
,
69 #ifdef CONFIG_PARAVIRT
70 .resume
= paravirt_clocksource_resume
,
73 static struct clocksource
*itc_clocksource
;
75 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
77 #include <linux/kernel_stat.h>
79 extern cputime_t
cycle_to_cputime(u64 cyc
);
82 * Called from the context switch with interrupts disabled, to charge all
83 * accumulated times to the current process, and to prepare accounting on
86 void ia64_account_on_switch(struct task_struct
*prev
, struct task_struct
*next
)
88 struct thread_info
*pi
= task_thread_info(prev
);
89 struct thread_info
*ni
= task_thread_info(next
);
90 cputime_t delta_stime
, delta_utime
;
95 delta_stime
= cycle_to_cputime(pi
->ac_stime
+ (now
- pi
->ac_stamp
));
96 if (idle_task(smp_processor_id()) != prev
)
97 account_system_time(prev
, 0, delta_stime
, delta_stime
);
99 account_idle_time(delta_stime
);
102 delta_utime
= cycle_to_cputime(pi
->ac_utime
);
103 account_user_time(prev
, delta_utime
, delta_utime
);
106 pi
->ac_stamp
= ni
->ac_stamp
= now
;
107 ni
->ac_stime
= ni
->ac_utime
= 0;
111 * Account time for a transition between system, hard irq or soft irq state.
112 * Note that this function is called with interrupts enabled.
114 void account_system_vtime(struct task_struct
*tsk
)
116 struct thread_info
*ti
= task_thread_info(tsk
);
118 cputime_t delta_stime
;
121 local_irq_save(flags
);
123 now
= ia64_get_itc();
125 delta_stime
= cycle_to_cputime(ti
->ac_stime
+ (now
- ti
->ac_stamp
));
126 if (irq_count() || idle_task(smp_processor_id()) != tsk
)
127 account_system_time(tsk
, 0, delta_stime
, delta_stime
);
129 account_idle_time(delta_stime
);
134 local_irq_restore(flags
);
136 EXPORT_SYMBOL_GPL(account_system_vtime
);
139 * Called from the timer interrupt handler to charge accumulated user time
140 * to the current process. Must be called with interrupts disabled.
142 void account_process_tick(struct task_struct
*p
, int user_tick
)
144 struct thread_info
*ti
= task_thread_info(p
);
145 cputime_t delta_utime
;
148 delta_utime
= cycle_to_cputime(ti
->ac_utime
);
149 account_user_time(p
, delta_utime
, delta_utime
);
154 #endif /* CONFIG_VIRT_CPU_ACCOUNTING */
157 timer_interrupt (int irq
, void *dev_id
)
159 unsigned long new_itm
;
161 if (unlikely(cpu_is_offline(smp_processor_id()))) {
165 platform_timer_interrupt(irq
, dev_id
);
167 new_itm
= local_cpu_data
->itm_next
;
169 if (!time_after(ia64_get_itc(), new_itm
))
170 printk(KERN_ERR
"Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
171 ia64_get_itc(), new_itm
);
173 profile_tick(CPU_PROFILING
);
175 if (paravirt_do_steal_accounting(&new_itm
))
176 goto skip_process_time_accounting
;
179 update_process_times(user_mode(get_irq_regs()));
181 new_itm
+= local_cpu_data
->itm_delta
;
183 if (smp_processor_id() == time_keeper_id
) {
185 * Here we are in the timer irq handler. We have irqs locally
186 * disabled, but we don't know if the timer_bh is running on
187 * another CPU. We need to avoid to SMP race by acquiring the
190 write_seqlock(&xtime_lock
);
192 local_cpu_data
->itm_next
= new_itm
;
193 write_sequnlock(&xtime_lock
);
195 local_cpu_data
->itm_next
= new_itm
;
197 if (time_after(new_itm
, ia64_get_itc()))
201 * Allow IPIs to interrupt the timer loop.
207 skip_process_time_accounting
:
211 * If we're too close to the next clock tick for
212 * comfort, we increase the safety margin by
213 * intentionally dropping the next tick(s). We do NOT
214 * update itm.next because that would force us to call
215 * do_timer() which in turn would let our clock run
216 * too fast (with the potentially devastating effect
217 * of losing monotony of time).
219 while (!time_after(new_itm
, ia64_get_itc() + local_cpu_data
->itm_delta
/2))
220 new_itm
+= local_cpu_data
->itm_delta
;
221 ia64_set_itm(new_itm
);
222 /* double check, in case we got hit by a (slow) PMI: */
223 } while (time_after_eq(ia64_get_itc(), new_itm
));
228 * Encapsulate access to the itm structure for SMP.
231 ia64_cpu_local_tick (void)
233 int cpu
= smp_processor_id();
234 unsigned long shift
= 0, delta
;
236 /* arrange for the cycle counter to generate a timer interrupt: */
237 ia64_set_itv(IA64_TIMER_VECTOR
);
239 delta
= local_cpu_data
->itm_delta
;
241 * Stagger the timer tick for each CPU so they don't occur all at (almost) the
245 unsigned long hi
= 1UL << ia64_fls(cpu
);
246 shift
= (2*(cpu
- hi
) + 1) * delta
/hi
/2;
248 local_cpu_data
->itm_next
= ia64_get_itc() + delta
+ shift
;
249 ia64_set_itm(local_cpu_data
->itm_next
);
254 static int __init
nojitter_setup(char *str
)
257 printk("Jitter checking for ITC timers disabled\n");
261 __setup("nojitter", nojitter_setup
);
267 unsigned long platform_base_freq
, itc_freq
;
268 struct pal_freq_ratio itc_ratio
, proc_ratio
;
269 long status
, platform_base_drift
, itc_drift
;
272 * According to SAL v2.6, we need to use a SAL call to determine the platform base
273 * frequency and then a PAL call to determine the frequency ratio between the ITC
274 * and the base frequency.
276 status
= ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM
,
277 &platform_base_freq
, &platform_base_drift
);
279 printk(KERN_ERR
"SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status
));
281 status
= ia64_pal_freq_ratios(&proc_ratio
, NULL
, &itc_ratio
);
283 printk(KERN_ERR
"PAL_FREQ_RATIOS failed with status=%ld\n", status
);
286 /* invent "random" values */
288 "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
289 platform_base_freq
= 100000000;
290 platform_base_drift
= -1; /* no drift info */
294 if (platform_base_freq
< 40000000) {
295 printk(KERN_ERR
"Platform base frequency %lu bogus---resetting to 75MHz!\n",
297 platform_base_freq
= 75000000;
298 platform_base_drift
= -1;
301 proc_ratio
.den
= 1; /* avoid division by zero */
303 itc_ratio
.den
= 1; /* avoid division by zero */
305 itc_freq
= (platform_base_freq
*itc_ratio
.num
)/itc_ratio
.den
;
307 local_cpu_data
->itm_delta
= (itc_freq
+ HZ
/2) / HZ
;
308 printk(KERN_DEBUG
"CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
309 "ITC freq=%lu.%03luMHz", smp_processor_id(),
310 platform_base_freq
/ 1000000, (platform_base_freq
/ 1000) % 1000,
311 itc_ratio
.num
, itc_ratio
.den
, itc_freq
/ 1000000, (itc_freq
/ 1000) % 1000);
313 if (platform_base_drift
!= -1) {
314 itc_drift
= platform_base_drift
*itc_ratio
.num
/itc_ratio
.den
;
315 printk("+/-%ldppm\n", itc_drift
);
321 local_cpu_data
->proc_freq
= (platform_base_freq
*proc_ratio
.num
)/proc_ratio
.den
;
322 local_cpu_data
->itc_freq
= itc_freq
;
323 local_cpu_data
->cyc_per_usec
= (itc_freq
+ USEC_PER_SEC
/2) / USEC_PER_SEC
;
324 local_cpu_data
->nsec_per_cyc
= ((NSEC_PER_SEC
<<IA64_NSEC_PER_CYC_SHIFT
)
325 + itc_freq
/2)/itc_freq
;
327 if (!(sal_platform_features
& IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT
)) {
329 /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
330 * Jitter compensation requires a cmpxchg which may limit
331 * the scalability of the syscalls for retrieving time.
332 * The ITC synchronization is usually successful to within a few
333 * ITC ticks but this is not a sure thing. If you need to improve
334 * timer performance in SMP situations then boot the kernel with the
335 * "nojitter" option. However, doing so may result in time fluctuating (maybe
336 * even going backward) if the ITC offsets between the individual CPUs
340 itc_jitter_data
.itc_jitter
= 1;
344 * ITC is drifty and we have not synchronized the ITCs in smpboot.c.
345 * ITC values may fluctuate significantly between processors.
346 * Clock should not be used for hrtimers. Mark itc as only
347 * useful for boot and testing.
349 * Note that jitter compensation is off! There is no point of
350 * synchronizing ITCs since they may be large differentials
351 * that change over time.
353 * The only way to fix this would be to repeatedly sync the
354 * ITCs. Until that time we have to avoid ITC.
356 clocksource_itc
.rating
= 50;
358 paravirt_init_missing_ticks_accounting(smp_processor_id());
360 /* avoid softlock up message when cpu is unplug and plugged again. */
361 touch_softlockup_watchdog();
363 /* Setup the CPU local timer tick */
364 ia64_cpu_local_tick();
366 if (!itc_clocksource
) {
367 /* Sort out mult/shift values: */
368 clocksource_itc
.mult
=
369 clocksource_hz2mult(local_cpu_data
->itc_freq
,
370 clocksource_itc
.shift
);
371 clocksource_register(&clocksource_itc
);
372 itc_clocksource
= &clocksource_itc
;
376 static cycle_t
itc_get_cycles(void)
378 u64 lcycle
, now
, ret
;
380 if (!itc_jitter_data
.itc_jitter
)
383 lcycle
= itc_jitter_data
.itc_lastcycle
;
385 if (lcycle
&& time_after(lcycle
, now
))
389 * Keep track of the last timer value returned.
390 * In an SMP environment, you could lose out in contention of
391 * cmpxchg. If so, your cmpxchg returns new value which the
392 * winner of contention updated to. Use the new value instead.
394 ret
= cmpxchg(&itc_jitter_data
.itc_lastcycle
, lcycle
, now
);
395 if (unlikely(ret
!= lcycle
))
402 static struct irqaction timer_irqaction
= {
403 .handler
= timer_interrupt
,
404 .flags
= IRQF_DISABLED
| IRQF_IRQPOLL
,
411 register_percpu_irq(IA64_TIMER_VECTOR
, &timer_irqaction
);
412 efi_gettimeofday(&xtime
);
416 * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
417 * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
419 set_normalized_timespec(&wall_to_monotonic
, -xtime
.tv_sec
, -xtime
.tv_nsec
);
423 * Generic udelay assumes that if preemption is allowed and the thread
424 * migrates to another CPU, that the ITC values are synchronized across
428 ia64_itc_udelay (unsigned long usecs
)
430 unsigned long start
= ia64_get_itc();
431 unsigned long end
= start
+ usecs
*local_cpu_data
->cyc_per_usec
;
433 while (time_before(ia64_get_itc(), end
))
437 void (*ia64_udelay
)(unsigned long usecs
) = &ia64_itc_udelay
;
440 udelay (unsigned long usecs
)
442 (*ia64_udelay
)(usecs
);
444 EXPORT_SYMBOL(udelay
);
446 /* IA64 doesn't cache the timezone */
447 void update_vsyscall_tz(void)
451 void update_vsyscall(struct timespec
*wall
, struct clocksource
*c
)
455 write_seqlock_irqsave(&fsyscall_gtod_data
.lock
, flags
);
457 /* copy fsyscall clock data */
458 fsyscall_gtod_data
.clk_mask
= c
->mask
;
459 fsyscall_gtod_data
.clk_mult
= c
->mult
;
460 fsyscall_gtod_data
.clk_shift
= c
->shift
;
461 fsyscall_gtod_data
.clk_fsys_mmio
= c
->fsys_mmio
;
462 fsyscall_gtod_data
.clk_cycle_last
= c
->cycle_last
;
464 /* copy kernel time structures */
465 fsyscall_gtod_data
.wall_time
.tv_sec
= wall
->tv_sec
;
466 fsyscall_gtod_data
.wall_time
.tv_nsec
= wall
->tv_nsec
;
467 fsyscall_gtod_data
.monotonic_time
.tv_sec
= wall_to_monotonic
.tv_sec
469 fsyscall_gtod_data
.monotonic_time
.tv_nsec
= wall_to_monotonic
.tv_nsec
473 while (fsyscall_gtod_data
.monotonic_time
.tv_nsec
>= NSEC_PER_SEC
) {
474 fsyscall_gtod_data
.monotonic_time
.tv_nsec
-= NSEC_PER_SEC
;
475 fsyscall_gtod_data
.monotonic_time
.tv_sec
++;
478 write_sequnlock_irqrestore(&fsyscall_gtod_data
.lock
, flags
);