2 * linux/arch/arm26/kernel/time.c
4 * Copyright (C) 1991, 1992, 1995 Linus Torvalds
5 * Modifications for ARM (C) 1994-2001 Russell King
6 * Mods for ARM26 (C) 2003 Ian Molton
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
12 * This file contains the ARM-specific time handling details:
13 * reading the RTC at bootup, etc...
15 * 1994-07-02 Alan Modra
16 * fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
17 * 1998-12-20 Updated NTP code according to technical memorandum Jan '96
18 * "A Kernel Model for Precision Timekeeping" by Dave Mills
21 #include <linux/module.h>
22 #include <linux/kernel.h>
23 #include <linux/interrupt.h>
24 #include <linux/time.h>
25 #include <linux/init.h>
26 #include <linux/smp.h>
27 #include <linux/timex.h>
28 #include <linux/errno.h>
29 #include <linux/profile.h>
31 #include <asm/hardware.h>
36 /* this needs a better home */
37 DEFINE_SPINLOCK(rtc_lock
);
39 /* change this if you have some constant time drift */
40 #define USECS_PER_JIFFY (1000000/HZ)
42 static int dummy_set_rtc(void)
48 * hook for setting the RTC's idea of the current time.
50 int (*set_rtc
)(void) = dummy_set_rtc
;
53 * Get time offset based on IOCs timer.
54 * FIXME - if this is called with interrutps off, why the shennanigans
57 static unsigned long gettimeoffset(void)
59 unsigned int count1
, count2
, status
;
62 ioc_writeb (0, IOC_T0LATCH
);
64 count1
= ioc_readb(IOC_T0CNTL
) | (ioc_readb(IOC_T0CNTH
) << 8);
66 status
= ioc_readb(IOC_IRQREQA
);
68 ioc_writeb (0, IOC_T0LATCH
);
70 count2
= ioc_readb(IOC_T0CNTL
) | (ioc_readb(IOC_T0CNTH
) << 8);
73 if (count2
< count1
) {
75 * We have not had an interrupt between reading count1
78 if (status
& (1 << 5))
80 } else if (count2
> count1
) {
82 * We have just had another interrupt between reading
88 offset
= (LATCH
- offset
) * (tick_nsec
/ 1000);
89 return (offset
+ LATCH
/2) / LATCH
;
93 * Scheduler clock - returns current time in nanosec units.
95 unsigned long long sched_clock(void)
97 return (unsigned long long)jiffies
* (1000000000 / HZ
);
100 static unsigned long next_rtc_update
;
103 * If we have an externally synchronized linux clock, then update
104 * CMOS clock accordingly every ~11 minutes. set_rtc() has to be
105 * called as close as possible to 500 ms before the new second
108 static inline void do_set_rtc(void)
110 if (!ntp_synced() || set_rtc
== NULL
)
113 //FIXME - timespec.tv_sec is a time_t not unsigned long
114 if (next_rtc_update
&&
115 time_before((unsigned long)xtime
.tv_sec
, next_rtc_update
))
118 if (xtime
.tv_nsec
< 500000000 - ((unsigned) tick_nsec
>> 1) &&
119 xtime
.tv_nsec
>= 500000000 + ((unsigned) tick_nsec
>> 1))
124 * rtc update failed. Try again in 60s
126 next_rtc_update
= xtime
.tv_sec
+ 60;
128 next_rtc_update
= xtime
.tv_sec
+ 660;
133 void do_gettimeofday(struct timeval
*tv
)
137 unsigned long usec
, sec
;
140 seq
= read_seqbegin_irqsave(&xtime_lock
, flags
);
141 usec
= gettimeoffset();
143 usec
+= xtime
.tv_nsec
/ 1000;
144 } while (read_seqretry_irqrestore(&xtime_lock
, seq
, flags
));
146 /* usec may have gone up a lot: be safe */
147 while (usec
>= 1000000) {
156 EXPORT_SYMBOL(do_gettimeofday
);
158 int do_settimeofday(struct timespec
*tv
)
160 if ((unsigned long)tv
->tv_nsec
>= NSEC_PER_SEC
)
163 write_seqlock_irq(&xtime_lock
);
165 * This is revolting. We need to set "xtime" correctly. However, the
166 * value in this location is the value at the most recent update of
167 * wall time. Discover what correction gettimeofday() would have
168 * done, and then undo it!
170 tv
->tv_nsec
-= 1000 * gettimeoffset();
172 while (tv
->tv_nsec
< 0) {
173 tv
->tv_nsec
+= NSEC_PER_SEC
;
177 xtime
.tv_sec
= tv
->tv_sec
;
178 xtime
.tv_nsec
= tv
->tv_nsec
;
180 write_sequnlock_irq(&xtime_lock
);
185 EXPORT_SYMBOL(do_settimeofday
);
187 static irqreturn_t
timer_interrupt(int irq
, void *dev_id
, struct pt_regs
*regs
)
191 update_process_times(user_mode(regs
));
193 do_set_rtc(); //FIME - EVERY timer IRQ?
194 profile_tick(CPU_PROFILING
, regs
);
195 return IRQ_HANDLED
; //FIXME - is this right?
198 static struct irqaction timer_irq
= {
200 .flags
= IRQF_DISABLED
,
201 .handler
= timer_interrupt
,
204 extern void ioctime_init(void);
207 * Set up timer interrupt.
209 void __init
time_init(void)
211 ioc_writeb(LATCH
& 255, IOC_T0LTCHL
);
212 ioc_writeb(LATCH
>> 8, IOC_T0LTCHH
);
213 ioc_writeb(0, IOC_T0GO
);
216 setup_irq(IRQ_TIMER
, &timer_irq
);