xref: /openbmc/linux/arch/ia64/kernel/time.c (revision f42b3800)
1 /*
2  * linux/arch/ia64/kernel/time.c
3  *
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>
10  */
11 
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>
23 
24 #include <asm/machvec.h>
25 #include <asm/delay.h>
26 #include <asm/hw_irq.h>
27 #include <asm/ptrace.h>
28 #include <asm/sal.h>
29 #include <asm/sections.h>
30 #include <asm/system.h>
31 
32 #include "fsyscall_gtod_data.h"
33 
34 static cycle_t itc_get_cycles(void);
35 
36 struct fsyscall_gtod_data_t fsyscall_gtod_data = {
37 	.lock = SEQLOCK_UNLOCKED,
38 };
39 
40 struct itc_jitter_data_t itc_jitter_data;
41 
42 volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
43 
44 #ifdef CONFIG_IA64_DEBUG_IRQ
45 
46 unsigned long last_cli_ip;
47 EXPORT_SYMBOL(last_cli_ip);
48 
49 #endif
50 
51 static struct clocksource clocksource_itc = {
52 	.name           = "itc",
53 	.rating         = 350,
54 	.read           = itc_get_cycles,
55 	.mask           = CLOCKSOURCE_MASK(64),
56 	.mult           = 0, /*to be calculated*/
57 	.shift          = 16,
58 	.flags          = CLOCK_SOURCE_IS_CONTINUOUS,
59 };
60 static struct clocksource *itc_clocksource;
61 
62 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
63 
64 #include <linux/kernel_stat.h>
65 
66 extern cputime_t cycle_to_cputime(u64 cyc);
67 
68 /*
69  * Called from the context switch with interrupts disabled, to charge all
70  * accumulated times to the current process, and to prepare accounting on
71  * the next process.
72  */
73 void ia64_account_on_switch(struct task_struct *prev, struct task_struct *next)
74 {
75 	struct thread_info *pi = task_thread_info(prev);
76 	struct thread_info *ni = task_thread_info(next);
77 	cputime_t delta_stime, delta_utime;
78 	__u64 now;
79 
80 	now = ia64_get_itc();
81 
82 	delta_stime = cycle_to_cputime(pi->ac_stime + (now - pi->ac_stamp));
83 	account_system_time(prev, 0, delta_stime);
84 	account_system_time_scaled(prev, delta_stime);
85 
86 	if (pi->ac_utime) {
87 		delta_utime = cycle_to_cputime(pi->ac_utime);
88 		account_user_time(prev, delta_utime);
89 		account_user_time_scaled(prev, delta_utime);
90 	}
91 
92 	pi->ac_stamp = ni->ac_stamp = now;
93 	ni->ac_stime = ni->ac_utime = 0;
94 }
95 
96 /*
97  * Account time for a transition between system, hard irq or soft irq state.
98  * Note that this function is called with interrupts enabled.
99  */
100 void account_system_vtime(struct task_struct *tsk)
101 {
102 	struct thread_info *ti = task_thread_info(tsk);
103 	unsigned long flags;
104 	cputime_t delta_stime;
105 	__u64 now;
106 
107 	local_irq_save(flags);
108 
109 	now = ia64_get_itc();
110 
111 	delta_stime = cycle_to_cputime(ti->ac_stime + (now - ti->ac_stamp));
112 	account_system_time(tsk, 0, delta_stime);
113 	account_system_time_scaled(tsk, delta_stime);
114 	ti->ac_stime = 0;
115 
116 	ti->ac_stamp = now;
117 
118 	local_irq_restore(flags);
119 }
120 
121 /*
122  * Called from the timer interrupt handler to charge accumulated user time
123  * to the current process.  Must be called with interrupts disabled.
124  */
125 void account_process_tick(struct task_struct *p, int user_tick)
126 {
127 	struct thread_info *ti = task_thread_info(p);
128 	cputime_t delta_utime;
129 
130 	if (ti->ac_utime) {
131 		delta_utime = cycle_to_cputime(ti->ac_utime);
132 		account_user_time(p, delta_utime);
133 		account_user_time_scaled(p, delta_utime);
134 		ti->ac_utime = 0;
135 	}
136 }
137 
138 #endif /* CONFIG_VIRT_CPU_ACCOUNTING */
139 
140 static irqreturn_t
141 timer_interrupt (int irq, void *dev_id)
142 {
143 	unsigned long new_itm;
144 
145 	if (unlikely(cpu_is_offline(smp_processor_id()))) {
146 		return IRQ_HANDLED;
147 	}
148 
149 	platform_timer_interrupt(irq, dev_id);
150 
151 	new_itm = local_cpu_data->itm_next;
152 
153 	if (!time_after(ia64_get_itc(), new_itm))
154 		printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
155 		       ia64_get_itc(), new_itm);
156 
157 	profile_tick(CPU_PROFILING);
158 
159 	while (1) {
160 		update_process_times(user_mode(get_irq_regs()));
161 
162 		new_itm += local_cpu_data->itm_delta;
163 
164 		if (smp_processor_id() == time_keeper_id) {
165 			/*
166 			 * Here we are in the timer irq handler. We have irqs locally
167 			 * disabled, but we don't know if the timer_bh is running on
168 			 * another CPU. We need to avoid to SMP race by acquiring the
169 			 * xtime_lock.
170 			 */
171 			write_seqlock(&xtime_lock);
172 			do_timer(1);
173 			local_cpu_data->itm_next = new_itm;
174 			write_sequnlock(&xtime_lock);
175 		} else
176 			local_cpu_data->itm_next = new_itm;
177 
178 		if (time_after(new_itm, ia64_get_itc()))
179 			break;
180 
181 		/*
182 		 * Allow IPIs to interrupt the timer loop.
183 		 */
184 		local_irq_enable();
185 		local_irq_disable();
186 	}
187 
188 	do {
189 		/*
190 		 * If we're too close to the next clock tick for
191 		 * comfort, we increase the safety margin by
192 		 * intentionally dropping the next tick(s).  We do NOT
193 		 * update itm.next because that would force us to call
194 		 * do_timer() which in turn would let our clock run
195 		 * too fast (with the potentially devastating effect
196 		 * of losing monotony of time).
197 		 */
198 		while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
199 			new_itm += local_cpu_data->itm_delta;
200 		ia64_set_itm(new_itm);
201 		/* double check, in case we got hit by a (slow) PMI: */
202 	} while (time_after_eq(ia64_get_itc(), new_itm));
203 	return IRQ_HANDLED;
204 }
205 
206 /*
207  * Encapsulate access to the itm structure for SMP.
208  */
209 void
210 ia64_cpu_local_tick (void)
211 {
212 	int cpu = smp_processor_id();
213 	unsigned long shift = 0, delta;
214 
215 	/* arrange for the cycle counter to generate a timer interrupt: */
216 	ia64_set_itv(IA64_TIMER_VECTOR);
217 
218 	delta = local_cpu_data->itm_delta;
219 	/*
220 	 * Stagger the timer tick for each CPU so they don't occur all at (almost) the
221 	 * same time:
222 	 */
223 	if (cpu) {
224 		unsigned long hi = 1UL << ia64_fls(cpu);
225 		shift = (2*(cpu - hi) + 1) * delta/hi/2;
226 	}
227 	local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
228 	ia64_set_itm(local_cpu_data->itm_next);
229 }
230 
231 static int nojitter;
232 
233 static int __init nojitter_setup(char *str)
234 {
235 	nojitter = 1;
236 	printk("Jitter checking for ITC timers disabled\n");
237 	return 1;
238 }
239 
240 __setup("nojitter", nojitter_setup);
241 
242 
243 void __devinit
244 ia64_init_itm (void)
245 {
246 	unsigned long platform_base_freq, itc_freq;
247 	struct pal_freq_ratio itc_ratio, proc_ratio;
248 	long status, platform_base_drift, itc_drift;
249 
250 	/*
251 	 * According to SAL v2.6, we need to use a SAL call to determine the platform base
252 	 * frequency and then a PAL call to determine the frequency ratio between the ITC
253 	 * and the base frequency.
254 	 */
255 	status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
256 				    &platform_base_freq, &platform_base_drift);
257 	if (status != 0) {
258 		printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
259 	} else {
260 		status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
261 		if (status != 0)
262 			printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
263 	}
264 	if (status != 0) {
265 		/* invent "random" values */
266 		printk(KERN_ERR
267 		       "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
268 		platform_base_freq = 100000000;
269 		platform_base_drift = -1;	/* no drift info */
270 		itc_ratio.num = 3;
271 		itc_ratio.den = 1;
272 	}
273 	if (platform_base_freq < 40000000) {
274 		printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
275 		       platform_base_freq);
276 		platform_base_freq = 75000000;
277 		platform_base_drift = -1;
278 	}
279 	if (!proc_ratio.den)
280 		proc_ratio.den = 1;	/* avoid division by zero */
281 	if (!itc_ratio.den)
282 		itc_ratio.den = 1;	/* avoid division by zero */
283 
284 	itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
285 
286 	local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
287 	printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
288 	       "ITC freq=%lu.%03luMHz", smp_processor_id(),
289 	       platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
290 	       itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
291 
292 	if (platform_base_drift != -1) {
293 		itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
294 		printk("+/-%ldppm\n", itc_drift);
295 	} else {
296 		itc_drift = -1;
297 		printk("\n");
298 	}
299 
300 	local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
301 	local_cpu_data->itc_freq = itc_freq;
302 	local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
303 	local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
304 					+ itc_freq/2)/itc_freq;
305 
306 	if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
307 #ifdef CONFIG_SMP
308 		/* On IA64 in an SMP configuration ITCs are never accurately synchronized.
309 		 * Jitter compensation requires a cmpxchg which may limit
310 		 * the scalability of the syscalls for retrieving time.
311 		 * The ITC synchronization is usually successful to within a few
312 		 * ITC ticks but this is not a sure thing. If you need to improve
313 		 * timer performance in SMP situations then boot the kernel with the
314 		 * "nojitter" option. However, doing so may result in time fluctuating (maybe
315 		 * even going backward) if the ITC offsets between the individual CPUs
316 		 * are too large.
317 		 */
318 		if (!nojitter)
319 			itc_jitter_data.itc_jitter = 1;
320 #endif
321 	} else
322 		/*
323 		 * ITC is drifty and we have not synchronized the ITCs in smpboot.c.
324 		 * ITC values may fluctuate significantly between processors.
325 		 * Clock should not be used for hrtimers. Mark itc as only
326 		 * useful for boot and testing.
327 		 *
328 		 * Note that jitter compensation is off! There is no point of
329 		 * synchronizing ITCs since they may be large differentials
330 		 * that change over time.
331 		 *
332 		 * The only way to fix this would be to repeatedly sync the
333 		 * ITCs. Until that time we have to avoid ITC.
334 		 */
335 		clocksource_itc.rating = 50;
336 
337 	/* Setup the CPU local timer tick */
338 	ia64_cpu_local_tick();
339 
340 	if (!itc_clocksource) {
341 		/* Sort out mult/shift values: */
342 		clocksource_itc.mult =
343 			clocksource_hz2mult(local_cpu_data->itc_freq,
344 						clocksource_itc.shift);
345 		clocksource_register(&clocksource_itc);
346 		itc_clocksource = &clocksource_itc;
347 	}
348 }
349 
350 static cycle_t itc_get_cycles(void)
351 {
352 	u64 lcycle, now, ret;
353 
354 	if (!itc_jitter_data.itc_jitter)
355 		return get_cycles();
356 
357 	lcycle = itc_jitter_data.itc_lastcycle;
358 	now = get_cycles();
359 	if (lcycle && time_after(lcycle, now))
360 		return lcycle;
361 
362 	/*
363 	 * Keep track of the last timer value returned.
364 	 * In an SMP environment, you could lose out in contention of
365 	 * cmpxchg. If so, your cmpxchg returns new value which the
366 	 * winner of contention updated to. Use the new value instead.
367 	 */
368 	ret = cmpxchg(&itc_jitter_data.itc_lastcycle, lcycle, now);
369 	if (unlikely(ret != lcycle))
370 		return ret;
371 
372 	return now;
373 }
374 
375 
376 static struct irqaction timer_irqaction = {
377 	.handler =	timer_interrupt,
378 	.flags =	IRQF_DISABLED | IRQF_IRQPOLL,
379 	.name =		"timer"
380 };
381 
382 void __devinit ia64_disable_timer(void)
383 {
384 	ia64_set_itv(1 << 16);
385 }
386 
387 void __init
388 time_init (void)
389 {
390 	register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
391 	efi_gettimeofday(&xtime);
392 	ia64_init_itm();
393 
394 	/*
395 	 * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
396 	 * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
397 	 */
398 	set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
399 }
400 
401 /*
402  * Generic udelay assumes that if preemption is allowed and the thread
403  * migrates to another CPU, that the ITC values are synchronized across
404  * all CPUs.
405  */
406 static void
407 ia64_itc_udelay (unsigned long usecs)
408 {
409 	unsigned long start = ia64_get_itc();
410 	unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
411 
412 	while (time_before(ia64_get_itc(), end))
413 		cpu_relax();
414 }
415 
416 void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
417 
418 void
419 udelay (unsigned long usecs)
420 {
421 	(*ia64_udelay)(usecs);
422 }
423 EXPORT_SYMBOL(udelay);
424 
425 /* IA64 doesn't cache the timezone */
426 void update_vsyscall_tz(void)
427 {
428 }
429 
430 void update_vsyscall(struct timespec *wall, struct clocksource *c)
431 {
432         unsigned long flags;
433 
434         write_seqlock_irqsave(&fsyscall_gtod_data.lock, flags);
435 
436         /* copy fsyscall clock data */
437         fsyscall_gtod_data.clk_mask = c->mask;
438         fsyscall_gtod_data.clk_mult = c->mult;
439         fsyscall_gtod_data.clk_shift = c->shift;
440         fsyscall_gtod_data.clk_fsys_mmio = c->fsys_mmio;
441         fsyscall_gtod_data.clk_cycle_last = c->cycle_last;
442 
443 	/* copy kernel time structures */
444         fsyscall_gtod_data.wall_time.tv_sec = wall->tv_sec;
445         fsyscall_gtod_data.wall_time.tv_nsec = wall->tv_nsec;
446         fsyscall_gtod_data.monotonic_time.tv_sec = wall_to_monotonic.tv_sec
447 							+ wall->tv_sec;
448         fsyscall_gtod_data.monotonic_time.tv_nsec = wall_to_monotonic.tv_nsec
449 							+ wall->tv_nsec;
450 
451 	/* normalize */
452 	while (fsyscall_gtod_data.monotonic_time.tv_nsec >= NSEC_PER_SEC) {
453 		fsyscall_gtod_data.monotonic_time.tv_nsec -= NSEC_PER_SEC;
454 		fsyscall_gtod_data.monotonic_time.tv_sec++;
455 	}
456 
457         write_sequnlock_irqrestore(&fsyscall_gtod_data.lock, flags);
458 }
459 
460