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