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1da177e4 LT |
1 | /* |
2 | * linux/arch/arm/mach-sa1100/time.c | |
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 | #include <linux/init.h> | |
12 | #include <linux/errno.h> | |
13 | #include <linux/interrupt.h> | |
14 | #include <linux/timex.h> | |
15 | #include <linux/signal.h> | |
16 | ||
17 | #include <asm/mach/time.h> | |
18 | #include <asm/hardware.h> | |
19 | ||
20 | #define RTC_DEF_DIVIDER (32768 - 1) | |
21 | #define RTC_DEF_TRIM 0 | |
22 | ||
23 | static unsigned long __init sa1100_get_rtc_time(void) | |
24 | { | |
25 | /* | |
26 | * According to the manual we should be able to let RTTR be zero | |
27 | * and then a default diviser for a 32.768KHz clock is used. | |
28 | * Apparently this doesn't work, at least for my SA1110 rev 5. | |
29 | * If the clock divider is uninitialized then reset it to the | |
30 | * default value to get the 1Hz clock. | |
31 | */ | |
32 | if (RTTR == 0) { | |
33 | RTTR = RTC_DEF_DIVIDER + (RTC_DEF_TRIM << 16); | |
34 | printk(KERN_WARNING "Warning: uninitialized Real Time Clock\n"); | |
35 | /* The current RTC value probably doesn't make sense either */ | |
36 | RCNR = 0; | |
37 | return 0; | |
38 | } | |
39 | return RCNR; | |
40 | } | |
41 | ||
42 | static int sa1100_set_rtc(void) | |
43 | { | |
44 | unsigned long current_time = xtime.tv_sec; | |
45 | ||
46 | if (RTSR & RTSR_ALE) { | |
47 | /* make sure not to forward the clock over an alarm */ | |
48 | unsigned long alarm = RTAR; | |
49 | if (current_time >= alarm && alarm >= RCNR) | |
50 | return -ERESTARTSYS; | |
51 | } | |
52 | RCNR = current_time; | |
53 | return 0; | |
54 | } | |
55 | ||
56 | /* IRQs are disabled before entering here from do_gettimeofday() */ | |
57 | static unsigned long sa1100_gettimeoffset (void) | |
58 | { | |
59 | unsigned long ticks_to_match, elapsed, usec; | |
60 | ||
61 | /* Get ticks before next timer match */ | |
62 | ticks_to_match = OSMR0 - OSCR; | |
63 | ||
64 | /* We need elapsed ticks since last match */ | |
65 | elapsed = LATCH - ticks_to_match; | |
66 | ||
67 | /* Now convert them to usec */ | |
68 | usec = (unsigned long)(elapsed * (tick_nsec / 1000))/LATCH; | |
69 | ||
70 | return usec; | |
71 | } | |
72 | ||
73 | /* | |
74 | * We will be entered with IRQs enabled. | |
75 | * | |
76 | * Loop until we get ahead of the free running timer. | |
77 | * This ensures an exact clock tick count and time accuracy. | |
78 | * IRQs are disabled inside the loop to ensure coherence between | |
79 | * lost_ticks (updated in do_timer()) and the match reg value, so we | |
80 | * can use do_gettimeofday() from interrupt handlers. | |
81 | */ | |
82 | static irqreturn_t | |
83 | sa1100_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs) | |
84 | { | |
85 | unsigned int next_match; | |
86 | ||
87 | write_seqlock(&xtime_lock); | |
88 | ||
89 | do { | |
90 | timer_tick(regs); | |
91 | OSSR = OSSR_M0; /* Clear match on timer 0 */ | |
92 | next_match = (OSMR0 += LATCH); | |
93 | } while ((signed long)(next_match - OSCR) <= 0); | |
94 | ||
95 | write_sequnlock(&xtime_lock); | |
96 | ||
97 | return IRQ_HANDLED; | |
98 | } | |
99 | ||
100 | static struct irqaction sa1100_timer_irq = { | |
101 | .name = "SA11xx Timer Tick", | |
102 | .flags = SA_INTERRUPT, | |
103 | .handler = sa1100_timer_interrupt | |
104 | }; | |
105 | ||
106 | static void __init sa1100_timer_init(void) | |
107 | { | |
108 | struct timespec tv; | |
109 | ||
110 | set_rtc = sa1100_set_rtc; | |
111 | ||
112 | tv.tv_nsec = 0; | |
113 | tv.tv_sec = sa1100_get_rtc_time(); | |
114 | do_settimeofday(&tv); | |
115 | ||
116 | OSMR0 = 0; /* set initial match at 0 */ | |
117 | OSSR = 0xf; /* clear status on all timers */ | |
118 | setup_irq(IRQ_OST0, &sa1100_timer_irq); | |
119 | OIER |= OIER_E0; /* enable match on timer 0 to cause interrupts */ | |
120 | OSCR = 0; /* initialize free-running timer, force first match */ | |
121 | } | |
122 | ||
123 | #ifdef CONFIG_PM | |
124 | unsigned long osmr[4], oier; | |
125 | ||
126 | static void sa1100_timer_suspend(void) | |
127 | { | |
128 | osmr[0] = OSMR0; | |
129 | osmr[1] = OSMR1; | |
130 | osmr[2] = OSMR2; | |
131 | osmr[3] = OSMR3; | |
132 | oier = OIER; | |
133 | } | |
134 | ||
135 | static void sa1100_timer_resume(void) | |
136 | { | |
137 | OSSR = 0x0f; | |
138 | OSMR0 = osmr[0]; | |
139 | OSMR1 = osmr[1]; | |
140 | OSMR2 = osmr[2]; | |
141 | OSMR3 = osmr[3]; | |
142 | OIER = oier; | |
143 | ||
144 | /* | |
145 | * OSMR0 is the system timer: make sure OSCR is sufficiently behind | |
146 | */ | |
147 | OSCR = OSMR0 - LATCH; | |
148 | } | |
149 | #else | |
150 | #define sa1100_timer_suspend NULL | |
151 | #define sa1100_timer_resume NULL | |
152 | #endif | |
153 | ||
154 | struct sys_timer sa1100_timer = { | |
155 | .init = sa1100_timer_init, | |
156 | .suspend = sa1100_timer_suspend, | |
157 | .resume = sa1100_timer_resume, | |
158 | .offset = sa1100_gettimeoffset, | |
159 | }; |