Linux 2.6.13-rc4
[linux-2.6/next.git] / arch / arm / mach-pxa / time.c
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1 /*
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>
25 #include <asm/io.h>
26 #include <asm/leds.h>
27 #include <asm/irq.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)
35 return RCNR;
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)
46 return -ERESTARTSYS;
48 RCNR = current_time;
49 return 0;
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() */
64 if (elapsed <= 0)
65 return 0;
67 /* Now convert them to usec */
68 usec = (unsigned long)(elapsed * (tick_nsec / 1000))/LATCH;
70 return usec;
73 static irqreturn_t
74 pxa_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
76 int next_match;
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.
95 do {
96 timer_tick(regs);
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);
103 return IRQ_HANDLED;
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)
114 struct timespec tv;
116 set_rtc = pxa_set_rtc;
118 tv.tv_nsec = 0;
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 */
129 #ifdef CONFIG_PM
130 static unsigned long osmr[4], oier;
132 static void pxa_timer_suspend(void)
134 osmr[0] = OSMR0;
135 osmr[1] = OSMR1;
136 osmr[2] = OSMR2;
137 osmr[3] = OSMR3;
138 oier = OIER;
141 static void pxa_timer_resume(void)
143 OSMR0 = osmr[0];
144 OSMR1 = osmr[1];
145 OSMR2 = osmr[2];
146 OSMR3 = osmr[3];
147 OIER = oier;
150 * OSMR0 is the system timer: make sure OSCR is sufficiently behind
152 OSCR = OSMR0 - LATCH;
154 #else
155 #define pxa_timer_suspend NULL
156 #define pxa_timer_resume NULL
157 #endif
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,