1 /* 2 * Delay loops based on the OpenRISC implementation. 3 * 4 * Copyright (C) 2012 ARM Limited 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, write to the Free Software 17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 18 * 19 * Author: Will Deacon <will.deacon@arm.com> 20 */ 21 22 #include <linux/delay.h> 23 #include <linux/init.h> 24 #include <linux/kernel.h> 25 #include <linux/module.h> 26 #include <linux/timex.h> 27 28 /* 29 * Default to the loop-based delay implementation. 30 */ 31 struct arm_delay_ops arm_delay_ops = { 32 .delay = __loop_delay, 33 .const_udelay = __loop_const_udelay, 34 .udelay = __loop_udelay, 35 }; 36 37 #ifdef ARCH_HAS_READ_CURRENT_TIMER 38 static void __timer_delay(unsigned long cycles) 39 { 40 cycles_t start = get_cycles(); 41 42 while ((get_cycles() - start) < cycles) 43 cpu_relax(); 44 } 45 46 static void __timer_const_udelay(unsigned long xloops) 47 { 48 unsigned long long loops = xloops; 49 loops *= loops_per_jiffy; 50 __timer_delay(loops >> UDELAY_SHIFT); 51 } 52 53 static void __timer_udelay(unsigned long usecs) 54 { 55 __timer_const_udelay(usecs * UDELAY_MULT); 56 } 57 58 void __init init_current_timer_delay(unsigned long freq) 59 { 60 pr_info("Switching to timer-based delay loop\n"); 61 lpj_fine = freq / HZ; 62 arm_delay_ops.delay = __timer_delay; 63 arm_delay_ops.const_udelay = __timer_const_udelay; 64 arm_delay_ops.udelay = __timer_udelay; 65 } 66 67 unsigned long __cpuinit calibrate_delay_is_known(void) 68 { 69 return lpj_fine; 70 } 71 #endif 72