2 * linux/arch/x86-64/kernel/time.c
4 * "High Precision Event Timer" based timekeeping.
6 * Copyright (c) 1991,1992,1995 Linus Torvalds
7 * Copyright (c) 1994 Alan Modra
8 * Copyright (c) 1995 Markus Kuhn
9 * Copyright (c) 1996 Ingo Molnar
10 * Copyright (c) 1998 Andrea Arcangeli
11 * Copyright (c) 2002,2006 Vojtech Pavlik
12 * Copyright (c) 2003 Andi Kleen
13 * RTC support code taken from arch/i386/kernel/timers/time_hpet.c
16 #include <linux/kernel.h>
17 #include <linux/sched.h>
18 #include <linux/interrupt.h>
19 #include <linux/init.h>
20 #include <linux/mc146818rtc.h>
21 #include <linux/time.h>
22 #include <linux/ioport.h>
23 #include <linux/module.h>
24 #include <linux/device.h>
25 #include <linux/sysdev.h>
26 #include <linux/bcd.h>
27 #include <linux/notifier.h>
28 #include <linux/cpu.h>
29 #include <linux/kallsyms.h>
30 #include <linux/acpi.h>
32 #include <acpi/achware.h> /* for PM timer frequency */
33 #include <acpi/acpi_bus.h>
35 #include <asm/8253pit.h>
36 #include <asm/pgtable.h>
37 #include <asm/vsyscall.h>
38 #include <asm/timex.h>
39 #include <asm/proto.h>
41 #include <asm/sections.h>
42 #include <linux/cpufreq.h>
43 #include <linux/hpet.h>
47 extern void i8254_timer_resume(void);
48 extern int using_apic_timer;
50 static char *timename = NULL;
52 DEFINE_SPINLOCK(rtc_lock);
53 EXPORT_SYMBOL(rtc_lock);
54 DEFINE_SPINLOCK(i8253_lock);
56 volatile unsigned long __jiffies __section_jiffies = INITIAL_JIFFIES;
58 unsigned long profile_pc(struct pt_regs *regs)
60 unsigned long pc = instruction_pointer(regs);
62 /* Assume the lock function has either no stack frame or a copy
64 Eflags always has bits 22 and up cleared unlike kernel addresses. */
65 if (!user_mode(regs) && in_lock_functions(pc)) {
66 unsigned long *sp = (unsigned long *)regs->rsp;
74 EXPORT_SYMBOL(profile_pc);
77 * In order to set the CMOS clock precisely, set_rtc_mmss has to be called 500
78 * ms after the second nowtime has started, because when nowtime is written
79 * into the registers of the CMOS clock, it will jump to the next second
80 * precisely 500 ms later. Check the Motorola MC146818A or Dallas DS12887 data
84 static void set_rtc_mmss(unsigned long nowtime)
86 int real_seconds, real_minutes, cmos_minutes;
87 unsigned char control, freq_select;
90 * IRQs are disabled when we're called from the timer interrupt,
91 * no need for spin_lock_irqsave()
97 * Tell the clock it's being set and stop it.
100 control = CMOS_READ(RTC_CONTROL);
101 CMOS_WRITE(control | RTC_SET, RTC_CONTROL);
103 freq_select = CMOS_READ(RTC_FREQ_SELECT);
104 CMOS_WRITE(freq_select | RTC_DIV_RESET2, RTC_FREQ_SELECT);
106 cmos_minutes = CMOS_READ(RTC_MINUTES);
107 BCD_TO_BIN(cmos_minutes);
110 * since we're only adjusting minutes and seconds, don't interfere with hour
111 * overflow. This avoids messing with unknown time zones but requires your RTC
112 * not to be off by more than 15 minutes. Since we're calling it only when
113 * our clock is externally synchronized using NTP, this shouldn't be a problem.
116 real_seconds = nowtime % 60;
117 real_minutes = nowtime / 60;
118 if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
119 real_minutes += 30; /* correct for half hour time zone */
122 if (abs(real_minutes - cmos_minutes) >= 30) {
123 printk(KERN_WARNING "time.c: can't update CMOS clock "
124 "from %d to %d\n", cmos_minutes, real_minutes);
126 BIN_TO_BCD(real_seconds);
127 BIN_TO_BCD(real_minutes);
128 CMOS_WRITE(real_seconds, RTC_SECONDS);
129 CMOS_WRITE(real_minutes, RTC_MINUTES);
133 * The following flags have to be released exactly in this order, otherwise the
134 * DS12887 (popular MC146818A clone with integrated battery and quartz) will
135 * not reset the oscillator and will not update precisely 500 ms later. You
136 * won't find this mentioned in the Dallas Semiconductor data sheets, but who
137 * believes data sheets anyway ... -- Markus Kuhn
140 CMOS_WRITE(control, RTC_CONTROL);
141 CMOS_WRITE(freq_select, RTC_FREQ_SELECT);
143 spin_unlock(&rtc_lock);
147 void main_timer_handler(void)
149 static unsigned long rtc_update = 0;
151 * Here we are in the timer irq handler. We have irqs locally disabled (so we
152 * don't need spin_lock_irqsave()) but we don't know if the timer_bh is running
153 * on the other CPU, so we need a lock. We also need to lock the vsyscall
154 * variables, because both do_timer() and us change them -arca+vojtech
157 write_seqlock(&xtime_lock);
160 * Do the timer stuff.
165 update_process_times(user_mode(get_irq_regs()));
169 * In the SMP case we use the local APIC timer interrupt to do the profiling,
170 * except when we simulate SMP mode on a uniprocessor system, in that case we
171 * have to call the local interrupt handler.
174 if (!using_apic_timer)
175 smp_local_timer_interrupt();
178 * If we have an externally synchronized Linux clock, then update CMOS clock
179 * accordingly every ~11 minutes. set_rtc_mmss() will be called in the jiffy
180 * closest to exactly 500 ms before the next second. If the update fails, we
181 * don't care, as it'll be updated on the next turn, and the problem (time way
182 * off) isn't likely to go away much sooner anyway.
185 if (ntp_synced() && xtime.tv_sec > rtc_update &&
186 abs(xtime.tv_nsec - 500000000) <= tick_nsec / 2) {
187 set_rtc_mmss(xtime.tv_sec);
188 rtc_update = xtime.tv_sec + 660;
191 write_sequnlock(&xtime_lock);
194 static irqreturn_t timer_interrupt(int irq, void *dev_id)
196 if (apic_runs_main_timer > 1)
198 main_timer_handler();
199 if (using_apic_timer)
200 smp_send_timer_broadcast_ipi();
204 static unsigned long get_cmos_time(void)
206 unsigned int year, mon, day, hour, min, sec;
208 unsigned century = 0;
210 spin_lock_irqsave(&rtc_lock, flags);
213 sec = CMOS_READ(RTC_SECONDS);
214 min = CMOS_READ(RTC_MINUTES);
215 hour = CMOS_READ(RTC_HOURS);
216 day = CMOS_READ(RTC_DAY_OF_MONTH);
217 mon = CMOS_READ(RTC_MONTH);
218 year = CMOS_READ(RTC_YEAR);
220 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
221 acpi_gbl_FADT.century)
222 century = CMOS_READ(acpi_gbl_FADT.century);
224 } while (sec != CMOS_READ(RTC_SECONDS));
226 spin_unlock_irqrestore(&rtc_lock, flags);
229 * We know that x86-64 always uses BCD format, no need to check the
242 year += century * 100;
243 printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
246 * x86-64 systems only exists since 2002.
247 * This will work up to Dec 31, 2100
252 return mktime(year, mon, day, hour, min, sec);
257 * pit_calibrate_tsc() uses the speaker output (channel 2) of
258 * the PIT. This is better than using the timer interrupt output,
259 * because we can read the value of the speaker with just one inb(),
260 * where we need three i/o operations for the interrupt channel.
261 * We count how many ticks the TSC does in 50 ms.
264 static unsigned int __init pit_calibrate_tsc(void)
266 unsigned long start, end;
269 spin_lock_irqsave(&i8253_lock, flags);
271 outb((inb(0x61) & ~0x02) | 0x01, 0x61);
274 outb((PIT_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
275 outb((PIT_TICK_RATE / (1000 / 50)) >> 8, 0x42);
276 start = get_cycles_sync();
277 while ((inb(0x61) & 0x20) == 0);
278 end = get_cycles_sync();
280 spin_unlock_irqrestore(&i8253_lock, flags);
282 return (end - start) / 50;
285 #define PIT_MODE 0x43
288 static void __init __pit_init(int val, u8 mode)
292 spin_lock_irqsave(&i8253_lock, flags);
293 outb_p(mode, PIT_MODE);
294 outb_p(val & 0xff, PIT_CH0); /* LSB */
295 outb_p(val >> 8, PIT_CH0); /* MSB */
296 spin_unlock_irqrestore(&i8253_lock, flags);
299 void __init pit_init(void)
301 __pit_init(LATCH, 0x34); /* binary, mode 2, LSB/MSB, ch 0 */
304 void __init pit_stop_interrupt(void)
306 __pit_init(0, 0x30); /* mode 0 */
309 void __init stop_timer_interrupt(void)
314 hpet_timer_stop_set_go(0);
317 pit_stop_interrupt();
319 printk(KERN_INFO "timer: %s interrupt stopped.\n", name);
322 static struct irqaction irq0 = {
323 timer_interrupt, IRQF_DISABLED, CPU_MASK_NONE, "timer", NULL, NULL
326 void __init time_init(void)
330 xtime.tv_sec = get_cmos_time();
333 set_normalized_timespec(&wall_to_monotonic,
334 -xtime.tv_sec, -xtime.tv_nsec);
336 if (hpet_arch_init())
339 if (hpet_use_timer) {
340 /* set tick_nsec to use the proper rate for HPET */
341 tick_nsec = TICK_NSEC_HPET;
342 cpu_khz = hpet_calibrate_tsc();
346 cpu_khz = pit_calibrate_tsc();
350 if (unsynchronized_tsc())
353 if (cpu_has(&boot_cpu_data, X86_FEATURE_RDTSCP))
354 vgetcpu_mode = VGETCPU_RDTSCP;
356 vgetcpu_mode = VGETCPU_LSL;
358 set_cyc2ns_scale(cpu_khz);
359 printk(KERN_INFO "time.c: Detected %d.%03d MHz processor.\n",
360 cpu_khz / 1000, cpu_khz % 1000);
365 static long clock_cmos_diff;
366 static unsigned long sleep_start;
369 * sysfs support for the timer.
372 static int timer_suspend(struct sys_device *dev, pm_message_t state)
375 * Estimate time zone so that set_time can update the clock
377 long cmos_time = get_cmos_time();
379 clock_cmos_diff = -cmos_time;
380 clock_cmos_diff += get_seconds();
381 sleep_start = cmos_time;
385 static int timer_resume(struct sys_device *dev)
389 unsigned long ctime = get_cmos_time();
390 long sleep_length = (ctime - sleep_start) * HZ;
392 if (sleep_length < 0) {
393 printk(KERN_WARNING "Time skew detected in timer resume!\n");
394 /* The time after the resume must not be earlier than the time
395 * before the suspend or some nasty things will happen
403 i8254_timer_resume();
405 sec = ctime + clock_cmos_diff;
406 write_seqlock_irqsave(&xtime_lock,flags);
409 jiffies += sleep_length;
410 write_sequnlock_irqrestore(&xtime_lock,flags);
411 touch_softlockup_watchdog();
415 static struct sysdev_class timer_sysclass = {
416 .resume = timer_resume,
417 .suspend = timer_suspend,
418 set_kset_name("timer"),
421 /* XXX this sysfs stuff should probably go elsewhere later -john */
422 static struct sys_device device_timer = {
424 .cls = &timer_sysclass,
427 static int time_init_device(void)
429 int error = sysdev_class_register(&timer_sysclass);
431 error = sysdev_register(&device_timer);
435 device_initcall(time_init_device);