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 xloops_to_cycles(unsigned long xloops)21static inline unsigned long xloops_to_cycles(unsigned long xloops) 22 { 23 return (xloops * loops_per_jiffy * HZ) >> 32; 24 } 25 26 /* 27 * Force the use of CNTVCT_EL0 in order to have the same base as WFxT. 28 * This avoids some annoying issues when CNTVOFF_EL2 is not reset 0 on a 29 * KVM host running at EL1 until we do a vcpu_put() on the vcpu. When 30 * running at EL2, the effective offset is always 0. 31 * 32 * Note that userspace cannot change the offset behind our back either, 33 * as the vcpu mutex is held as long as KVM_RUN is in progress. 34 */ __delay_cycles(void)35static cycles_t notrace __delay_cycles(void) 36 { 37 guard(preempt_notrace)(); 38 return __arch_counter_get_cntvct_stable(); 39 } 40 __delay(unsigned long cycles)41void __delay(unsigned long cycles) 42 { 43 cycles_t start = __delay_cycles(); 44 45 if (alternative_has_cap_unlikely(ARM64_HAS_WFXT)) { 46 u64 end = start + cycles; 47 48 /* 49 * Start with WFIT. If an interrupt makes us resume 50 * early, use a WFET loop to complete the delay. 51 */ 52 wfit(end); 53 while ((__delay_cycles() - start) < cycles) 54 wfet(end); 55 } else if (arch_timer_evtstrm_available()) { 56 const cycles_t timer_evt_period = 57 USECS_TO_CYCLES(ARCH_TIMER_EVT_STREAM_PERIOD_US); 58 59 while ((__delay_cycles() - start + timer_evt_period) < cycles) 60 wfe(); 61 } 62 63 while ((__delay_cycles() - start) < cycles) 64 cpu_relax(); 65 } 66 EXPORT_SYMBOL(__delay); 67 __const_udelay(unsigned long xloops)68inline void __const_udelay(unsigned long xloops) 69 { 70 __delay(xloops_to_cycles(xloops)); 71 } 72 EXPORT_SYMBOL(__const_udelay); 73 __udelay(unsigned long usecs)74void __udelay(unsigned long usecs) 75 { 76 __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */ 77 } 78 EXPORT_SYMBOL(__udelay); 79 __ndelay(unsigned long nsecs)80void __ndelay(unsigned long nsecs) 81 { 82 __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */ 83 } 84 EXPORT_SYMBOL(__ndelay); 85