2 * arch/arm/mach-pxa/time.c
4 * Author: Nicolas Pitre
5 * Created: Jun 15, 2001
6 * Copyright: MontaVista Software Inc.
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.
13 #include <linux/config.h>
14 #include <linux/kernel.h>
15 #include <linux/init.h>
16 #include <linux/delay.h>
17 #include <linux/interrupt.h>
18 #include <linux/time.h>
19 #include <linux/signal.h>
20 #include <linux/errno.h>
21 #include <linux/sched.h>
23 #include <asm/system.h>
24 #include <asm/hardware.h>
28 #include <asm/mach/irq.h>
29 #include <asm/mach/time.h>
30 #include <asm/arch/pxa-regs.h>
33 static inline unsigned long pxa_get_rtc_time(void)
38 static int pxa_set_rtc(void)
40 unsigned long current_time
= xtime
.tv_sec
;
42 if (RTSR
& RTSR_ALE
) {
43 /* make sure not to forward the clock over an alarm */
44 unsigned long alarm
= RTAR
;
45 if (current_time
>= alarm
&& alarm
>= RCNR
)
52 /* IRQs are disabled before entering here from do_gettimeofday() */
53 static unsigned long pxa_gettimeoffset (void)
55 long ticks_to_match
, elapsed
, usec
;
57 /* Get ticks before next timer match */
58 ticks_to_match
= OSMR0
- OSCR
;
60 /* We need elapsed ticks since last match */
61 elapsed
= LATCH
- ticks_to_match
;
63 /* don't get fooled by the workaround in pxa_timer_interrupt() */
67 /* Now convert them to usec */
68 usec
= (unsigned long)(elapsed
* (tick_nsec
/ 1000))/LATCH
;
74 pxa_timer_interrupt(int irq
, void *dev_id
, struct pt_regs
*regs
)
78 write_seqlock(&xtime_lock
);
80 /* Loop until we get ahead of the free running timer.
81 * This ensures an exact clock tick count and time accuracy.
82 * IRQs are disabled inside the loop to ensure coherence between
83 * lost_ticks (updated in do_timer()) and the match reg value, so we
84 * can use do_gettimeofday() from interrupt handlers.
86 * HACK ALERT: it seems that the PXA timer regs aren't updated right
87 * away in all cases when a write occurs. We therefore compare with
88 * 8 instead of 0 in the while() condition below to avoid missing a
89 * match if OSCR has already reached the next OSMR value.
90 * Experience has shown that up to 6 ticks are needed to work around
91 * this problem, but let's use 8 to be conservative. Note that this
92 * affect things only when the timer IRQ has been delayed by nearly
93 * exactly one tick period which should be a pretty rare event.
97 OSSR
= OSSR_M0
; /* Clear match on timer 0 */
98 next_match
= (OSMR0
+= LATCH
);
99 } while( (signed long)(next_match
- OSCR
) <= 8 );
101 write_sequnlock(&xtime_lock
);
106 static struct irqaction pxa_timer_irq
= {
107 .name
= "PXA Timer Tick",
108 .flags
= SA_INTERRUPT
| SA_TIMER
,
109 .handler
= pxa_timer_interrupt
,
112 static void __init
pxa_timer_init(void)
116 set_rtc
= pxa_set_rtc
;
119 tv
.tv_sec
= pxa_get_rtc_time();
120 do_settimeofday(&tv
);
122 OSMR0
= 0; /* set initial match at 0 */
123 OSSR
= 0xf; /* clear status on all timers */
124 setup_irq(IRQ_OST0
, &pxa_timer_irq
);
125 OIER
|= OIER_E0
; /* enable match on timer 0 to cause interrupts */
126 OSCR
= 0; /* initialize free-running timer, force first match */
130 static unsigned long osmr
[4], oier
;
132 static void pxa_timer_suspend(void)
141 static void pxa_timer_resume(void)
150 * OSMR0 is the system timer: make sure OSCR is sufficiently behind
152 OSCR
= OSMR0
- LATCH
;
155 #define pxa_timer_suspend NULL
156 #define pxa_timer_resume NULL
159 struct sys_timer pxa_timer
= {
160 .init
= pxa_timer_init
,
161 .suspend
= pxa_timer_suspend
,
162 .resume
= pxa_timer_resume
,
163 .offset
= pxa_gettimeoffset
,