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 /* 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 */ 35 #define __delay_cycles() __arch_counter_get_cntvct_stable() 36 37 void __delay(unsigned long cycles) 38 { 39 cycles_t start = __delay_cycles(); 40 41 if (alternative_has_cap_unlikely(ARM64_HAS_WFXT)) { 42 u64 end = start + cycles; 43 44 /* 45 * Start with WFIT. If an interrupt makes us resume 46 * early, use a WFET loop to complete the delay. 47 */ 48 wfit(end); 49 while ((__delay_cycles() - start) < cycles) 50 wfet(end); 51 } else if (arch_timer_evtstrm_available()) { 52 const cycles_t timer_evt_period = 53 USECS_TO_CYCLES(ARCH_TIMER_EVT_STREAM_PERIOD_US); 54 55 while ((__delay_cycles() - start + timer_evt_period) < cycles) 56 wfe(); 57 } 58 59 while ((__delay_cycles() - start) < cycles) 60 cpu_relax(); 61 } 62 EXPORT_SYMBOL(__delay); 63 64 inline void __const_udelay(unsigned long xloops) 65 { 66 __delay(xloops_to_cycles(xloops)); 67 } 68 EXPORT_SYMBOL(__const_udelay); 69 70 void __udelay(unsigned long usecs) 71 { 72 __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */ 73 } 74 EXPORT_SYMBOL(__udelay); 75 76 void __ndelay(unsigned long nsecs) 77 { 78 __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */ 79 } 80 EXPORT_SYMBOL(__ndelay); 81