2 * linux/arch/arm/mach-sa1100/time.c
4 * Copyright (C) 1998 Deborah Wallach.
5 * Twiddles (C) 1999 Hugo Fiennes <hugo@empeg.com>
7 * 2000/03/29 (C) Nicolas Pitre <nico@cam.org>
8 * Rewritten: big cleanup, much simpler, better HZ accuracy.
11 #include <linux/init.h>
12 #include <linux/errno.h>
13 #include <linux/interrupt.h>
14 #include <linux/irq.h>
15 #include <linux/timex.h>
16 #include <linux/signal.h>
18 #include <asm/mach/time.h>
19 #include <asm/hardware.h>
21 #define RTC_DEF_DIVIDER (32768 - 1)
22 #define RTC_DEF_TRIM 0
24 static unsigned long __init
sa1100_get_rtc_time(void)
27 * According to the manual we should be able to let RTTR be zero
28 * and then a default divisor for a 32.768KHz clock is used.
29 * Apparently this doesn't work, at least for my SA1110 rev 5.
30 * If the clock divider is uninitialized then reset it to the
31 * default value to get the 1Hz clock.
34 RTTR
= RTC_DEF_DIVIDER
+ (RTC_DEF_TRIM
<< 16);
35 printk(KERN_WARNING
"Warning: uninitialized Real Time Clock\n");
36 /* The current RTC value probably doesn't make sense either */
43 static int sa1100_set_rtc(void)
45 unsigned long current_time
= xtime
.tv_sec
;
47 if (RTSR
& RTSR_ALE
) {
48 /* make sure not to forward the clock over an alarm */
49 unsigned long alarm
= RTAR
;
50 if (current_time
>= alarm
&& alarm
>= RCNR
)
57 /* IRQs are disabled before entering here from do_gettimeofday() */
58 static unsigned long sa1100_gettimeoffset (void)
60 unsigned long ticks_to_match
, elapsed
, usec
;
62 /* Get ticks before next timer match */
63 ticks_to_match
= OSMR0
- OSCR
;
65 /* We need elapsed ticks since last match */
66 elapsed
= LATCH
- ticks_to_match
;
68 /* Now convert them to usec */
69 usec
= (unsigned long)(elapsed
* (tick_nsec
/ 1000))/LATCH
;
74 #ifdef CONFIG_NO_IDLE_HZ
75 static unsigned long initial_match
;
76 static int match_posponed
;
80 sa1100_timer_interrupt(int irq
, void *dev_id
)
82 unsigned int next_match
;
84 write_seqlock(&xtime_lock
);
86 #ifdef CONFIG_NO_IDLE_HZ
89 OSMR0
= initial_match
;
94 * Loop until we get ahead of the free running timer.
95 * This ensures an exact clock tick count and time accuracy.
96 * Since IRQs are disabled at this point, coherence between
97 * lost_ticks(updated in do_timer()) and the match reg value is
98 * ensured, hence we can use do_gettimeofday() from interrupt
103 OSSR
= OSSR_M0
; /* Clear match on timer 0 */
104 next_match
= (OSMR0
+= LATCH
);
105 } while ((signed long)(next_match
- OSCR
) <= 0);
107 write_sequnlock(&xtime_lock
);
112 static struct irqaction sa1100_timer_irq
= {
113 .name
= "SA11xx Timer Tick",
114 .flags
= IRQF_DISABLED
| IRQF_TIMER
| IRQF_IRQPOLL
,
115 .handler
= sa1100_timer_interrupt
,
118 static void __init
sa1100_timer_init(void)
123 set_rtc
= sa1100_set_rtc
;
126 tv
.tv_sec
= sa1100_get_rtc_time();
127 do_settimeofday(&tv
);
129 OIER
= 0; /* disable any timer interrupts */
130 OSSR
= 0xf; /* clear status on all timers */
131 setup_irq(IRQ_OST0
, &sa1100_timer_irq
);
132 local_irq_save(flags
);
133 OIER
= OIER_E0
; /* enable match on timer 0 to cause interrupts */
134 OSMR0
= OSCR
+ LATCH
; /* set initial match */
135 local_irq_restore(flags
);
138 #ifdef CONFIG_NO_IDLE_HZ
139 static int sa1100_dyn_tick_enable_disable(void)
145 static void sa1100_dyn_tick_reprogram(unsigned long ticks
)
148 initial_match
= OSMR0
;
149 OSMR0
= initial_match
+ ticks
* LATCH
;
155 sa1100_dyn_tick_handler(int irq
, void *dev_id
)
157 if (match_posponed
) {
159 OSMR0
= initial_match
;
160 if ((signed long)(initial_match
- OSCR
) <= 0)
161 return sa1100_timer_interrupt(irq
, dev_id
);
166 static struct dyn_tick_timer sa1100_dyn_tick
= {
167 .enable
= sa1100_dyn_tick_enable_disable
,
168 .disable
= sa1100_dyn_tick_enable_disable
,
169 .reprogram
= sa1100_dyn_tick_reprogram
,
170 .handler
= sa1100_dyn_tick_handler
,
175 unsigned long osmr
[4], oier
;
177 static void sa1100_timer_suspend(void)
186 static void sa1100_timer_resume(void)
196 * OSMR0 is the system timer: make sure OSCR is sufficiently behind
198 OSCR
= OSMR0
- LATCH
;
201 #define sa1100_timer_suspend NULL
202 #define sa1100_timer_resume NULL
205 struct sys_timer sa1100_timer
= {
206 .init
= sa1100_timer_init
,
207 .suspend
= sa1100_timer_suspend
,
208 .resume
= sa1100_timer_resume
,
209 .offset
= sa1100_gettimeoffset
,
210 #ifdef CONFIG_NO_IDLE_HZ
211 .dyn_tick
= &sa1100_dyn_tick
,