1/*
2 * arch/xtensa/kernel/time.c
3 *
4 * Timer and clock support.
5 *
6 * This file is subject to the terms and conditions of the GNU General Public
7 * License.  See the file "COPYING" in the main directory of this archive
8 * for more details.
9 *
10 * Copyright (C) 2005 Tensilica Inc.
11 *
12 * Chris Zankel <chris@zankel.net>
13 */
14
15#include <linux/errno.h>
16#include <linux/sched.h>
17#include <linux/time.h>
18#include <linux/clocksource.h>
19#include <linux/interrupt.h>
20#include <linux/module.h>
21#include <linux/init.h>
22#include <linux/irq.h>
23#include <linux/profile.h>
24#include <linux/delay.h>
25
26#include <asm/timex.h>
27#include <asm/platform.h>
28
29#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
30unsigned long ccount_per_jiffy;		/* per 1/HZ */
31unsigned long nsec_per_ccount;		/* nsec per ccount increment */
32#endif
33
34static cycle_t ccount_read(void)
35{
36	return (cycle_t)get_ccount();
37}
38
39static struct clocksource ccount_clocksource = {
40	.name = "ccount",
41	.rating = 200,
42	.read = ccount_read,
43	.mask = CLOCKSOURCE_MASK(32),
44};
45
46static irqreturn_t timer_interrupt(int irq, void *dev_id);
47static struct irqaction timer_irqaction = {
48	.handler =	timer_interrupt,
49	.flags =	IRQF_DISABLED,
50	.name =		"timer",
51};
52
53void __init time_init(void)
54{
55#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
56	printk("Calibrating CPU frequency ");
57	platform_calibrate_ccount();
58	printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),
59			(int)(ccount_per_jiffy/(10000/HZ))%100);
60#endif
61	clocksource_register_hz(&ccount_clocksource, CCOUNT_PER_JIFFY * HZ);
62
63	/* Initialize the linux timer interrupt. */
64
65	setup_irq(LINUX_TIMER_INT, &timer_irqaction);
66	set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
67}
68
69/*
70 * The timer interrupt is called HZ times per second.
71 */
72
73irqreturn_t timer_interrupt (int irq, void *dev_id)
74{
75
76	unsigned long next;
77
78	next = get_linux_timer();
79
80again:
81	while ((signed long)(get_ccount() - next) > 0) {
82
83		profile_tick(CPU_PROFILING);
84#ifndef CONFIG_SMP
85		update_process_times(user_mode(get_irq_regs()));
86#endif
87
88		xtime_update(1); /* Linux handler in kernel/time/timekeeping */
89
90		/* Note that writing CCOMPARE clears the interrupt. */
91
92		next += CCOUNT_PER_JIFFY;
93		set_linux_timer(next);
94	}
95
96	/* Allow platform to do something useful (Wdog). */
97
98	platform_heartbeat();
99
100	/* Make sure we didn't miss any tick... */
101
102	if ((signed long)(get_ccount() - next) > 0)
103		goto again;
104
105	return IRQ_HANDLED;
106}
107
108#ifndef CONFIG_GENERIC_CALIBRATE_DELAY
109void __cpuinit calibrate_delay(void)
110{
111	loops_per_jiffy = CCOUNT_PER_JIFFY;
112	printk("Calibrating delay loop (skipped)... "
113	       "%lu.%02lu BogoMIPS preset\n",
114	       loops_per_jiffy/(1000000/HZ),
115	       (loops_per_jiffy/(10000/HZ)) % 100);
116}
117#endif
118