1 /* 2 * linux/arch/arm/kernel/arch_timer.c 3 * 4 * Copyright (C) 2011 ARM Ltd. 5 * All Rights Reserved 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 */ 11 #include <linux/init.h> 12 #include <linux/types.h> 13 #include <linux/errno.h> 14 15 #include <asm/delay.h> 16 #include <asm/sched_clock.h> 17 18 #include <clocksource/arm_arch_timer.h> 19 20 static unsigned long arch_timer_read_counter_long(void) 21 { 22 return arch_timer_read_counter(); 23 } 24 25 static u32 sched_clock_mult __read_mostly; 26 27 static unsigned long long notrace arch_timer_sched_clock(void) 28 { 29 return arch_timer_read_counter() * sched_clock_mult; 30 } 31 32 static struct delay_timer arch_delay_timer; 33 34 static void __init arch_timer_delay_timer_register(void) 35 { 36 /* Use the architected timer for the delay loop. */ 37 arch_delay_timer.read_current_timer = arch_timer_read_counter_long; 38 arch_delay_timer.freq = arch_timer_get_rate(); 39 register_current_timer_delay(&arch_delay_timer); 40 } 41 42 int __init arch_timer_of_register(void) 43 { 44 int ret; 45 46 ret = arch_timer_init(); 47 if (ret) 48 return ret; 49 50 arch_timer_delay_timer_register(); 51 52 return 0; 53 } 54 55 int __init arch_timer_sched_clock_init(void) 56 { 57 u32 arch_timer_rate = arch_timer_get_rate(); 58 59 if (arch_timer_rate == 0) 60 return -ENXIO; 61 62 /* Cache the sched_clock multiplier to save a divide in the hot path. */ 63 sched_clock_mult = NSEC_PER_SEC / arch_timer_rate; 64 sched_clock_func = arch_timer_sched_clock; 65 pr_info("sched_clock: ARM arch timer >56 bits at %ukHz, resolution %uns\n", 66 arch_timer_rate / 1000, sched_clock_mult); 67 68 return 0; 69 } 70