1/*
2 * linux/include/asm-arm/arch-sa1100/time.h
3 *
4 * Copyright (C) 1998 Deborah Wallach.
5 * Twiddles  (C) 1999 	Hugo Fiennes <hugo@empeg.com>
6 *
7 * 2000/03/29 (C) Nicolas Pitre <nico@cam.org>
8 *	Rewritten: big cleanup, much simpler, better HZ accuracy.
9 *
10 */
11
12
13#define RTC_DEF_DIVIDER		(32768 - 1)
14#define RTC_DEF_TRIM            0
15
16static unsigned long __init sa1100_get_rtc_time(void)
17{
18	/*
19	 * According to the manual we should be able to let RTTR be zero
20	 * and then a default diviser for a 32.768KHz clock is used.
21	 * Apparently this doesn't work, at least for my SA1110 rev 5.
22	 * If the clock divider is uninitialized then reset it to the
23	 * default value to get the 1Hz clock.
24	 */
25	if (RTTR == 0) {
26		RTTR = RTC_DEF_DIVIDER + (RTC_DEF_TRIM << 16);
27		printk(KERN_WARNING "Warning: uninitialized Real Time Clock\n");
28		/* The current RTC value probably doesn't make sense either */
29		RCNR = 0;
30		return 0;
31	}
32	return RCNR;
33}
34
35static int sa1100_set_rtc(void)
36{
37	unsigned long current_time = xtime.tv_sec;
38
39	if (RTSR & RTSR_ALE) {
40		/* make sure not to forward the clock over an alarm */
41		unsigned long alarm = RTAR;
42		if (current_time >= alarm && alarm >= RCNR)
43			return -ERESTARTSYS;
44	}
45	RCNR = current_time;
46	return 0;
47}
48
49/* IRQs are disabled before entering here from do_gettimeofday() */
50static unsigned long sa1100_gettimeoffset (void)
51{
52	unsigned long ticks_to_match, elapsed, usec;
53
54	/* Get ticks before next timer match */
55	ticks_to_match = OSMR0 - OSCR;
56
57	/* We need elapsed ticks since last match */
58	elapsed = LATCH - ticks_to_match;
59
60	/* Now convert them to usec */
61	usec = (unsigned long)(elapsed*tick)/LATCH;
62
63	return usec;
64}
65
66static void sa1100_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
67{
68	long flags;
69	int next_match;
70
71	/* Loop until we get ahead of the free running timer.
72	 * This ensures an exact clock tick count and time acuracy.
73	 * IRQs are disabled inside the loop to ensure coherence between
74	 * lost_ticks (updated in do_timer()) and the match reg value, so we
75	 * can use do_gettimeofday() from interrupt handlers.
76	 */
77	do {
78		do_leds();
79		do_set_rtc();
80		save_flags_cli( flags );
81		do_timer(regs);
82		OSSR = OSSR_M0;  /* Clear match on timer 0 */
83		next_match = (OSMR0 += LATCH);
84		restore_flags( flags );
85	} while( (signed long)(next_match - OSCR) <= 0 );
86}
87
88static inline void setup_timer (void)
89{
90	gettimeoffset = sa1100_gettimeoffset;
91	set_rtc = sa1100_set_rtc;
92	xtime.tv_sec = sa1100_get_rtc_time();
93	timer_irq.handler = sa1100_timer_interrupt;
94	OSMR0 = 0;		/* set initial match at 0 */
95	OSSR = 0xf;		/* clear status on all timers */
96	setup_arm_irq(IRQ_OST0, &timer_irq);
97	OIER |= OIER_E0;	/* enable match on timer 0 to cause interrupts */
98	OSCR = 0;		/* initialize free-running timer, force first match */
99}
100
101