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, see <http://www.gnu.org/licenses/>. 17 * 18 * Author: Will Deacon <will.deacon@arm.com> 19 */ 20 21 #include <linux/delay.h> 22 #include <linux/init.h> 23 #include <linux/kernel.h> 24 #include <linux/module.h> 25 #include <linux/timex.h> 26 27 #include <clocksource/arm_arch_timer.h> 28 29 #define USECS_TO_CYCLES(time_usecs) \ 30 xloops_to_cycles((time_usecs) * 0x10C7UL) 31 32 static inline unsigned long xloops_to_cycles(unsigned long xloops) 33 { 34 return (xloops * loops_per_jiffy * HZ) >> 32; 35 } 36 37 void __delay(unsigned long cycles) 38 { 39 cycles_t start = get_cycles(); 40 41 if (arch_timer_evtstrm_available()) { 42 const cycles_t timer_evt_period = 43 USECS_TO_CYCLES(ARCH_TIMER_EVT_STREAM_PERIOD_US); 44 45 while ((get_cycles() - start + timer_evt_period) < cycles) 46 wfe(); 47 } 48 49 while ((get_cycles() - start) < cycles) 50 cpu_relax(); 51 } 52 EXPORT_SYMBOL(__delay); 53 54 inline void __const_udelay(unsigned long xloops) 55 { 56 __delay(xloops_to_cycles(xloops)); 57 } 58 EXPORT_SYMBOL(__const_udelay); 59 60 void __udelay(unsigned long usecs) 61 { 62 __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */ 63 } 64 EXPORT_SYMBOL(__udelay); 65 66 void __ndelay(unsigned long nsecs) 67 { 68 __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */ 69 } 70 EXPORT_SYMBOL(__ndelay); 71