xref: /openbmc/u-boot/arch/arm/cpu/arm920t/ep93xx/timer.c (revision 441cac10)
1 /*
2  * Cirrus Logic EP93xx timer support.
3  *
4  * Copyright (C) 2009, 2010 Matthias Kaehlcke <matthias@kaehlcke.net>
5  *
6  * Copyright (C) 2004, 2005
7  * Cory T. Tusar, Videon Central, Inc., <ctusar@videon-central.com>
8  *
9  * Based on the original intr.c Cirrus Logic EP93xx Rev D. interrupt support,
10  * author unknown.
11  *
12  * See file CREDITS for list of people who contributed to this project.
13  *
14  * This program is free software; you can redistribute it and/or modify
15  * it under the terms of the GNU General Public License as published by
16  * the Free Software Foundation; either version 2 of the License, or
17  * (at your option) any later version.
18  *
19  * This program is distributed in the hope that it will be useful, but
20  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
21  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
22  * for more details.
23  *
24  * You should have received a copy of the GNU General Public License along
25  * with this program; if not, write to the Free Software Foundation, Inc.,
26  * 675 Mass Ave, Cambridge, MA 02139, USA.
27  */
28 
29 #include <common.h>
30 #include <linux/types.h>
31 #include <asm/arch/ep93xx.h>
32 #include <asm/io.h>
33 #include <div64.h>
34 
35 #define TIMER_CLKSEL	(1 << 3)
36 #define TIMER_ENABLE	(1 << 7)
37 
38 #define TIMER_FREQ			508469		/* ticks / second */
39 #define TIMER_MAX_VAL			0xFFFFFFFF
40 
41 static struct ep93xx_timer
42 {
43 	unsigned long long ticks;
44 	unsigned long last_read;
45 } timer;
46 
47 static inline unsigned long long usecs_to_ticks(unsigned long usecs)
48 {
49 	unsigned long long ticks = (unsigned long long)usecs * TIMER_FREQ;
50 	do_div(ticks, 1000 * 1000);
51 
52 	return ticks;
53 }
54 
55 static inline void read_timer(void)
56 {
57 	struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
58 	const unsigned long now = TIMER_MAX_VAL - readl(&timer_regs->timer3.value);
59 
60 	if (now >= timer.last_read)
61 		timer.ticks += now - timer.last_read;
62 	else
63 		/* an overflow occurred */
64 		timer.ticks += TIMER_MAX_VAL - timer.last_read + now;
65 
66 	timer.last_read = now;
67 }
68 
69 /*
70  * Get the number of ticks (in CONFIG_SYS_HZ resolution)
71  */
72 unsigned long long get_ticks(void)
73 {
74 	unsigned long long sys_ticks;
75 
76 	read_timer();
77 
78 	sys_ticks = timer.ticks * CONFIG_SYS_HZ;
79 	do_div(sys_ticks, TIMER_FREQ);
80 
81 	return sys_ticks;
82 }
83 
84 unsigned long get_timer_masked(void)
85 {
86 	return get_ticks();
87 }
88 
89 unsigned long get_timer(unsigned long base)
90 {
91 	return get_timer_masked() - base;
92 }
93 
94 void reset_timer_masked(void)
95 {
96 	read_timer();
97 	timer.ticks = 0;
98 }
99 
100 void reset_timer(void)
101 {
102 	reset_timer_masked();
103 }
104 
105 void __udelay(unsigned long usec)
106 {
107 	unsigned long long target;
108 
109 	read_timer();
110 
111 	target = timer.ticks + usecs_to_ticks(usec);
112 
113 	while (timer.ticks < target)
114 		read_timer();
115 }
116 
117 int timer_init(void)
118 {
119 	struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
120 
121 	/* use timer 3 with 508KHz and free running, not enabled now */
122 	writel(TIMER_CLKSEL, &timer_regs->timer3.control);
123 
124 	/* set initial timer value */
125 	writel(TIMER_MAX_VAL, &timer_regs->timer3.load);
126 
127 	/* Enable the timer */
128 	writel(TIMER_ENABLE | TIMER_CLKSEL,
129 		&timer_regs->timer3.control);
130 
131 	reset_timer_masked();
132 
133 	return 0;
134 }
135 
136 /*
137  * This function is derived from PowerPC code (timebase clock frequency).
138  * On ARM it returns the number of timer ticks per second.
139  */
140 unsigned long get_tbclk(void)
141 {
142 	return CONFIG_SYS_HZ;
143 }
144