1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Delay loops based on the OpenRISC implementation. 4 * 5 * Copyright (C) 2012 ARM Limited 6 * 7 * Author: Will Deacon <will.deacon@arm.com> 8 */ 9 10 #include <linux/delay.h> 11 #include <linux/init.h> 12 #include <linux/kernel.h> 13 #include <linux/module.h> 14 #include <linux/timex.h> 15 16 #include <clocksource/arm_arch_timer.h> 17 18 #define USECS_TO_CYCLES(time_usecs) \ 19 xloops_to_cycles((time_usecs) * 0x10C7UL) 20 21 static inline unsigned long xloops_to_cycles(unsigned long xloops) 22 { 23 return (xloops * loops_per_jiffy * HZ) >> 32; 24 } 25 26 void __delay(unsigned long cycles) 27 { 28 cycles_t start = get_cycles(); 29 30 if (alternative_has_cap_unlikely(ARM64_HAS_WFXT)) { 31 u64 end = start + cycles; 32 33 /* 34 * Start with WFIT. If an interrupt makes us resume 35 * early, use a WFET loop to complete the delay. 36 */ 37 wfit(end); 38 while ((get_cycles() - start) < cycles) 39 wfet(end); 40 } else if (arch_timer_evtstrm_available()) { 41 const cycles_t timer_evt_period = 42 USECS_TO_CYCLES(ARCH_TIMER_EVT_STREAM_PERIOD_US); 43 44 while ((get_cycles() - start + timer_evt_period) < cycles) 45 wfe(); 46 } 47 48 while ((get_cycles() - start) < cycles) 49 cpu_relax(); 50 } 51 EXPORT_SYMBOL(__delay); 52 53 inline void __const_udelay(unsigned long xloops) 54 { 55 __delay(xloops_to_cycles(xloops)); 56 } 57 EXPORT_SYMBOL(__const_udelay); 58 59 void __udelay(unsigned long usecs) 60 { 61 __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */ 62 } 63 EXPORT_SYMBOL(__udelay); 64 65 void __ndelay(unsigned long nsecs) 66 { 67 __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */ 68 } 69 EXPORT_SYMBOL(__ndelay); 70