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
30 unsigned long ccount_per_jiffy; /* per 1/HZ */
31 unsigned long nsec_per_ccount; /* nsec per ccount increment */
32 #endif
33
ccount_read(void)34 static cycle_t ccount_read(void)
35 {
36 return (cycle_t)get_ccount();
37 }
38
39 static struct clocksource ccount_clocksource = {
40 .name = "ccount",
41 .rating = 200,
42 .read = ccount_read,
43 .mask = CLOCKSOURCE_MASK(32),
44 /*
45 * With a shift of 22 the lower limit of the cpu clock is
46 * 1MHz, where NSEC_PER_CCOUNT is 1000 or a bit less than
47 * 2^10: Since we have 32 bits and the multiplicator can
48 * already take up as much as 10 bits, this leaves us with
49 * remaining upper 22 bits.
50 */
51 .shift = 22,
52 };
53
54 static irqreturn_t timer_interrupt(int irq, void *dev_id);
55 static struct irqaction timer_irqaction = {
56 .handler = timer_interrupt,
57 .flags = IRQF_DISABLED,
58 .name = "timer",
59 };
60
time_init(void)61 void __init time_init(void)
62 {
63 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
64 printk("Calibrating CPU frequency ");
65 platform_calibrate_ccount();
66 printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),
67 (int)(ccount_per_jiffy/(10000/HZ))%100);
68 #endif
69 ccount_clocksource.mult =
70 clocksource_hz2mult(CCOUNT_PER_JIFFY * HZ,
71 ccount_clocksource.shift);
72 clocksource_register(&ccount_clocksource);
73
74 /* Initialize the linux timer interrupt. */
75
76 setup_irq(LINUX_TIMER_INT, &timer_irqaction);
77 set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
78 }
79
80 /*
81 * The timer interrupt is called HZ times per second.
82 */
83
timer_interrupt(int irq,void * dev_id)84 irqreturn_t timer_interrupt (int irq, void *dev_id)
85 {
86
87 unsigned long next;
88
89 next = get_linux_timer();
90
91 again:
92 while ((signed long)(get_ccount() - next) > 0) {
93
94 profile_tick(CPU_PROFILING);
95 #ifndef CONFIG_SMP
96 update_process_times(user_mode(get_irq_regs()));
97 #endif
98
99 xtime_update(1); /* Linux handler in kernel/time/timekeeping */
100
101 /* Note that writing CCOMPARE clears the interrupt. */
102
103 next += CCOUNT_PER_JIFFY;
104 set_linux_timer(next);
105 }
106
107 /* Allow platform to do something useful (Wdog). */
108
109 platform_heartbeat();
110
111 /* Make sure we didn't miss any tick... */
112
113 if ((signed long)(get_ccount() - next) > 0)
114 goto again;
115
116 return IRQ_HANDLED;
117 }
118
119 #ifndef CONFIG_GENERIC_CALIBRATE_DELAY
calibrate_delay(void)120 void __cpuinit calibrate_delay(void)
121 {
122 loops_per_jiffy = CCOUNT_PER_JIFFY;
123 printk("Calibrating delay loop (skipped)... "
124 "%lu.%02lu BogoMIPS preset\n",
125 loops_per_jiffy/(1000000/HZ),
126 (loops_per_jiffy/(10000/HZ)) % 100);
127 }
128 #endif
129