1 /*
2 * linux/arch/arm/mach-at91/at91sam926x_time.c
3 *
4 * Copyright (C) 2005-2006 M. Amine SAYA, ATMEL Rousset, France
5 * Revision 2005 M. Nicolas Diremdjian, ATMEL Rousset, France
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 version 2 as
9 * published by the Free Software Foundation.
10 */
11
12 #include <linux/init.h>
13 #include <linux/interrupt.h>
14 #include <linux/irq.h>
15 #include <linux/kernel.h>
16 #include <linux/sched.h>
17 #include <linux/time.h>
18
19 #include <asm/hardware.h>
20 #include <asm/io.h>
21 #include <asm/mach/time.h>
22
23 #include <asm/arch/at91_pit.h>
24
25
26 #define PIT_CPIV(x) ((x) & AT91_PIT_CPIV)
27 #define PIT_PICNT(x) (((x) & AT91_PIT_PICNT) >> 20)
28
29 /*
30 * Returns number of microseconds since last timer interrupt. Note that interrupts
31 * will have been disabled by do_gettimeofday()
32 * 'LATCH' is hwclock ticks (see CLOCK_TICK_RATE in timex.h) per jiffy.
33 */
34 static unsigned long at91sam926x_gettimeoffset(void)
35 {
36 unsigned long elapsed;
37 unsigned long t = at91_sys_read(AT91_PIT_PIIR);
38
39 elapsed = (PIT_PICNT(t) * LATCH) + PIT_CPIV(t); /* hardware clock cycles */
40
41 return (unsigned long)(elapsed * jiffies_to_usecs(1)) / LATCH;
42 }
43
44 /*
45 * IRQ handler for the timer.
46 */
47 static irqreturn_t at91sam926x_timer_interrupt(int irq, void *dev_id)
48 {
49 volatile long nr_ticks;
50
51 if (at91_sys_read(AT91_PIT_SR) & AT91_PIT_PITS) { /* This is a shared interrupt */
52 /* Get number to ticks performed before interrupt and clear PIT interrupt */
53 nr_ticks = PIT_PICNT(at91_sys_read(AT91_PIT_PIVR));
54 do {
55 timer_tick();
56 nr_ticks--;
57 } while (nr_ticks);
58
59 return IRQ_HANDLED;
60 } else
61 return IRQ_NONE; /* not handled */
62 }
63
64 static struct irqaction at91sam926x_timer_irq = {
65 .name = "at91_tick",
66 .flags = IRQF_SHARED | IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
67 .handler = at91sam926x_timer_interrupt
68 };
69
70 void at91sam926x_timer_reset(void)
71 {
72 /* Disable timer */
73 at91_sys_write(AT91_PIT_MR, 0);
74
75 /* Clear any pending interrupts */
76 (void) at91_sys_read(AT91_PIT_PIVR);
77
78 /* Set Period Interval timer and enable its interrupt */
79 at91_sys_write(AT91_PIT_MR, (LATCH & AT91_PIT_PIV) | AT91_PIT_PITIEN | AT91_PIT_PITEN);
80 }
81
82 /*
83 * Set up timer interrupt.
84 */
85 void __init at91sam926x_timer_init(void)
86 {
87 /* Initialize and enable the timer */
88 at91sam926x_timer_reset();
89
90 /* Make IRQs happen for the system timer. */
91 setup_irq(AT91_ID_SYS, &at91sam926x_timer_irq);
92 }
93
94 #ifdef CONFIG_PM
95 static void at91sam926x_timer_suspend(void)
96 {
97 /* Disable timer */
98 at91_sys_write(AT91_PIT_MR, 0);
99 }
100 #else
101 #define at91sam926x_timer_suspend NULL
102 #endif
103
104 struct sys_timer at91sam926x_timer = {
105 .init = at91sam926x_timer_init,
106 .offset = at91sam926x_gettimeoffset,
107 .suspend = at91sam926x_timer_suspend,
108 .resume = at91sam926x_timer_reset,
109 };
110
111
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