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 /* Loop until we get ahead of the free running timer.
79 * This ensures an exact clock tick count and time accuracy.
80 * IRQs are disabled inside the loop to ensure coherence between
81 * lost_ticks (updated in do_timer()) and the match reg value, so we
82 * can use do_gettimeofday() from interrupt handlers.
84 * HACK ALERT: it seems that the PXA timer regs aren't updated right
85 * away in all cases when a write occurs. We therefore compare with
86 * 8 instead of 0 in the while() condition below to avoid missing a
87 * match if OSCR has already reached the next OSMR value.
88 * Experience has shown that up to 6 ticks are needed to work around
89 * this problem, but let's use 8 to be conservative. Note that this
90 * affect things only when the timer IRQ has been delayed by nearly
91 * exactly one tick period which should be a pretty rare event.
95 OSSR = OSSR_M0; /* Clear match on timer 0 */
96 next_match = (OSMR0 += LATCH);
97 } while( (signed long)(next_match - OSCR) <= 8 );
102 static struct irqaction pxa_timer_irq = {
103 .name = "PXA Timer Tick",
104 .flags = SA_INTERRUPT,
105 .handler = pxa_timer_interrupt
108 void __init pxa_init_time(void)
112 gettimeoffset = pxa_gettimeoffset;
113 set_rtc = pxa_set_rtc;
116 tv.tv_sec = pxa_get_rtc_time();
117 do_settimeofday(&tv);
119 OSMR0 = 0; /* set initial match at 0 */
120 OSSR = 0xf; /* clear status on all timers */
121 setup_irq(IRQ_OST0, &pxa_timer_irq);
122 OIER |= OIER_E0; /* enable match on timer 0 to cause interrupts */
123 OSCR = 0; /* initialize free-running timer, force first match */