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Diffstat (limited to 'arch/arm/mach-at91rm9200/at91rm9200_time.c')
-rw-r--r--arch/arm/mach-at91rm9200/at91rm9200_time.c141
1 files changed, 141 insertions, 0 deletions
diff --git a/arch/arm/mach-at91rm9200/at91rm9200_time.c b/arch/arm/mach-at91rm9200/at91rm9200_time.c
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index 000000000000..dc38e06ada63
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1/*
2 * linux/arch/arm/mach-at91rm9200/at91rm9200_time.c
3 *
4 * Copyright (C) 2003 SAN People
5 * Copyright (C) 2003 ATMEL
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20 */
21
22#include <linux/init.h>
23#include <linux/interrupt.h>
24#include <linux/kernel.h>
25#include <linux/sched.h>
26#include <linux/time.h>
27
28#include <asm/hardware.h>
29#include <asm/io.h>
30#include <asm/irq.h>
31#include <asm/mach/time.h>
32
33static unsigned long last_crtr;
34
35/*
36 * The ST_CRTR is updated asynchronously to the master clock. It is therefore
37 * necessary to read it twice (with the same value) to ensure accuracy.
38 */
39static inline unsigned long read_CRTR(void) {
40 unsigned long x1, x2;
41
42 do {
43 x1 = at91_sys_read(AT91_ST_CRTR);
44 x2 = at91_sys_read(AT91_ST_CRTR);
45 } while (x1 != x2);
46
47 return x1;
48}
49
50/*
51 * Returns number of microseconds since last timer interrupt. Note that interrupts
52 * will have been disabled by do_gettimeofday()
53 * 'LATCH' is hwclock ticks (see CLOCK_TICK_RATE in timex.h) per jiffy.
54 * 'tick' is usecs per jiffy (linux/timex.h).
55 */
56static unsigned long at91rm9200_gettimeoffset(void)
57{
58 unsigned long elapsed;
59
60 elapsed = (read_CRTR() - last_crtr) & AT91_ST_ALMV;
61
62 return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;
63}
64
65/*
66 * IRQ handler for the timer.
67 */
68static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
69{
70 if (at91_sys_read(AT91_ST_SR) & AT91_ST_PITS) { /* This is a shared interrupt */
71 write_seqlock(&xtime_lock);
72
73 while (((read_CRTR() - last_crtr) & AT91_ST_ALMV) >= LATCH) {
74 timer_tick(regs);
75 last_crtr = (last_crtr + LATCH) & AT91_ST_ALMV;
76 }
77
78 write_sequnlock(&xtime_lock);
79
80 return IRQ_HANDLED;
81 }
82 else
83 return IRQ_NONE; /* not handled */
84}
85
86static struct irqaction at91rm9200_timer_irq = {
87 .name = "at91_tick",
88 .flags = SA_SHIRQ | SA_INTERRUPT | SA_TIMER,
89 .handler = at91rm9200_timer_interrupt
90};
91
92void at91rm9200_timer_reset(void)
93{
94 last_crtr = 0;
95
96 /* Real time counter incremented every 30.51758 microseconds */
97 at91_sys_write(AT91_ST_RTMR, 1);
98
99 /* Set Period Interval timer */
100 at91_sys_write(AT91_ST_PIMR, LATCH);
101
102 /* Enable Period Interval Timer interrupt */
103 at91_sys_write(AT91_ST_IER, AT91_ST_PITS);
104}
105
106/*
107 * Set up timer interrupt.
108 */
109void __init at91rm9200_timer_init(void)
110{
111 /* Disable all timer interrupts */
112 at91_sys_write(AT91_ST_IDR, AT91_ST_PITS | AT91_ST_WDOVF | AT91_ST_RTTINC | AT91_ST_ALMS);
113 (void) at91_sys_read(AT91_ST_SR); /* Clear any pending interrupts */
114
115 /* Make IRQs happen for the system timer */
116 setup_irq(AT91_ID_SYS, &at91rm9200_timer_irq);
117
118 /* Change the kernel's 'tick' value to 10009 usec. (the default is 10000) */
119 tick_usec = (LATCH * 1000000) / CLOCK_TICK_RATE;
120
121 /* Initialize and enable the timer interrupt */
122 at91rm9200_timer_reset();
123}
124
125#ifdef CONFIG_PM
126static void at91rm9200_timer_suspend(void)
127{
128 /* disable Period Interval Timer interrupt */
129 at91_sys_write(AT91_ST_IDR, AT91_ST_PITS);
130}
131#else
132#define at91rm9200_timer_suspend NULL
133#endif
134
135struct sys_timer at91rm9200_timer = {
136 .init = at91rm9200_timer_init,
137 .offset = at91rm9200_gettimeoffset,
138 .suspend = at91rm9200_timer_suspend,
139 .resume = at91rm9200_timer_reset,
140};
141