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 <linux/types.h>
16 #include <asm/arch/ep93xx.h>
17 #include <asm/io.h>
18 #include <div64.h>
19
20 #define TIMER_CLKSEL (1 << 3)
21 #define TIMER_ENABLE (1 << 7)
22
23 #define TIMER_FREQ 508469 /* ticks / second */
24 #define TIMER_MAX_VAL 0xFFFFFFFF
25
26 static struct ep93xx_timer
27 {
28 unsigned long long ticks;
29 unsigned long last_read;
30 } timer;
31
usecs_to_ticks(unsigned long usecs)32 static inline unsigned long long usecs_to_ticks(unsigned long usecs)
33 {
34 unsigned long long ticks = (unsigned long long)usecs * TIMER_FREQ;
35 do_div(ticks, 1000 * 1000);
36
37 return ticks;
38 }
39
read_timer(void)40 static inline void read_timer(void)
41 {
42 struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
43 const unsigned long now = TIMER_MAX_VAL - readl(&timer_regs->timer3.value);
44
45 if (now >= timer.last_read)
46 timer.ticks += now - timer.last_read;
47 else
48 /* an overflow occurred */
49 timer.ticks += TIMER_MAX_VAL - timer.last_read + now;
50
51 timer.last_read = now;
52 }
53
54 /*
55 * Get the number of ticks (in CONFIG_SYS_HZ resolution)
56 */
get_ticks(void)57 unsigned long long get_ticks(void)
58 {
59 unsigned long long sys_ticks;
60
61 read_timer();
62
63 sys_ticks = timer.ticks * CONFIG_SYS_HZ;
64 do_div(sys_ticks, TIMER_FREQ);
65
66 return sys_ticks;
67 }
68
get_timer(unsigned long base)69 unsigned long get_timer(unsigned long base)
70 {
71 return get_ticks() - base;
72 }
73
__udelay(unsigned long usec)74 void __udelay(unsigned long usec)
75 {
76 unsigned long long target;
77
78 read_timer();
79
80 target = timer.ticks + usecs_to_ticks(usec);
81
82 while (timer.ticks < target)
83 read_timer();
84 }
85
timer_init(void)86 int timer_init(void)
87 {
88 struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
89
90 /* use timer 3 with 508KHz and free running, not enabled now */
91 writel(TIMER_CLKSEL, &timer_regs->timer3.control);
92
93 /* set initial timer value */
94 writel(TIMER_MAX_VAL, &timer_regs->timer3.load);
95
96 /* Enable the timer */
97 writel(TIMER_ENABLE | TIMER_CLKSEL,
98 &timer_regs->timer3.control);
99
100 /* Reset the timer */
101 read_timer();
102 timer.ticks = 0;
103
104 return 0;
105 }
106
107 /*
108 * This function is derived from PowerPC code (timebase clock frequency).
109 * On ARM it returns the number of timer ticks per second.
110 */
get_tbclk(void)111 unsigned long get_tbclk(void)
112 {
113 return CONFIG_SYS_HZ;
114 }
115