1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Cirrus Logic EP93xx timer support.
4 *
5 * Copyright (C) 2009, 2010 Matthias Kaehlcke <matthias@kaehlcke.net>
6 *
7 * Copyright (C) 2004, 2005
8 * Cory T. Tusar, Videon Central, Inc., <ctusar@videon-central.com>
9 *
10 * Based on the original intr.c Cirrus Logic EP93xx Rev D. interrupt support,
11 * author unknown.
12 */
13
14 #include <common.h>
15 #include <time.h>
16 #include <linux/types.h>
17 #include <asm/arch/ep93xx.h>
18 #include <asm/io.h>
19 #include <div64.h>
20
21 #define TIMER_CLKSEL (1 << 3)
22 #define TIMER_ENABLE (1 << 7)
23
24 #define TIMER_FREQ 508469 /* ticks / second */
25 #define TIMER_MAX_VAL 0xFFFFFFFF
26
27 static struct ep93xx_timer
28 {
29 unsigned long long ticks;
30 unsigned long last_read;
31 } timer;
32
usecs_to_ticks(unsigned long usecs)33 static inline unsigned long long usecs_to_ticks(unsigned long usecs)
34 {
35 unsigned long long ticks = (unsigned long long)usecs * TIMER_FREQ;
36 do_div(ticks, 1000 * 1000);
37
38 return ticks;
39 }
40
read_timer(void)41 static inline void read_timer(void)
42 {
43 struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
44 const unsigned long now = TIMER_MAX_VAL - readl(&timer_regs->timer3.value);
45
46 if (now >= timer.last_read)
47 timer.ticks += now - timer.last_read;
48 else
49 /* an overflow occurred */
50 timer.ticks += TIMER_MAX_VAL - timer.last_read + now;
51
52 timer.last_read = now;
53 }
54
55 /*
56 * Get the number of ticks (in CONFIG_SYS_HZ resolution)
57 */
get_ticks(void)58 unsigned long long get_ticks(void)
59 {
60 unsigned long long sys_ticks;
61
62 read_timer();
63
64 sys_ticks = timer.ticks * CONFIG_SYS_HZ;
65 do_div(sys_ticks, TIMER_FREQ);
66
67 return sys_ticks;
68 }
69
get_timer(unsigned long base)70 unsigned long get_timer(unsigned long base)
71 {
72 return get_ticks() - base;
73 }
74
__udelay(unsigned long usec)75 void __udelay(unsigned long usec)
76 {
77 unsigned long long target;
78
79 read_timer();
80
81 target = timer.ticks + usecs_to_ticks(usec);
82
83 while (timer.ticks < target)
84 read_timer();
85 }
86
timer_init(void)87 int timer_init(void)
88 {
89 struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
90
91 /* use timer 3 with 508KHz and free running, not enabled now */
92 writel(TIMER_CLKSEL, &timer_regs->timer3.control);
93
94 /* set initial timer value */
95 writel(TIMER_MAX_VAL, &timer_regs->timer3.load);
96
97 /* Enable the timer */
98 writel(TIMER_ENABLE | TIMER_CLKSEL,
99 &timer_regs->timer3.control);
100
101 /* Reset the timer */
102 read_timer();
103 timer.ticks = 0;
104
105 return 0;
106 }
107
108 /*
109 * This function is derived from PowerPC code (timebase clock frequency).
110 * On ARM it returns the number of timer ticks per second.
111 */
get_tbclk(void)112 unsigned long get_tbclk(void)
113 {
114 return CONFIG_SYS_HZ;
115 }
116