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 * SPDX-License-Identifier: GPL-2.0+ 13 */ 14 15 #include <common.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 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 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 */ 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 70 unsigned long get_timer_masked(void) 71 { 72 return get_ticks(); 73 } 74 75 unsigned long get_timer(unsigned long base) 76 { 77 return get_timer_masked() - base; 78 } 79 80 void __udelay(unsigned long usec) 81 { 82 unsigned long long target; 83 84 read_timer(); 85 86 target = timer.ticks + usecs_to_ticks(usec); 87 88 while (timer.ticks < target) 89 read_timer(); 90 } 91 92 int timer_init(void) 93 { 94 struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE; 95 96 /* use timer 3 with 508KHz and free running, not enabled now */ 97 writel(TIMER_CLKSEL, &timer_regs->timer3.control); 98 99 /* set initial timer value */ 100 writel(TIMER_MAX_VAL, &timer_regs->timer3.load); 101 102 /* Enable the timer */ 103 writel(TIMER_ENABLE | TIMER_CLKSEL, 104 &timer_regs->timer3.control); 105 106 /* Reset the timer */ 107 read_timer(); 108 timer.ticks = 0; 109 110 return 0; 111 } 112 113 /* 114 * This function is derived from PowerPC code (timebase clock frequency). 115 * On ARM it returns the number of timer ticks per second. 116 */ 117 unsigned long get_tbclk(void) 118 { 119 return CONFIG_SYS_HZ; 120 } 121