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