udelay.c (1179B)
1// SPDX-License-Identifier: GPL-2.0 2/* 3 * Copyright (C) 1993, 2000 Linus Torvalds 4 * 5 * Delay routines, using a pre-computed "loops_per_jiffy" value. 6 */ 7 8#include <linux/module.h> 9#include <linux/sched.h> /* for udelay's use of smp_processor_id */ 10#include <asm/param.h> 11#include <asm/smp.h> 12#include <linux/delay.h> 13 14/* 15 * Use only for very small delays (< 1 msec). 16 * 17 * The active part of our cycle counter is only 32-bits wide, and 18 * we're treating the difference between two marks as signed. On 19 * a 1GHz box, that's about 2 seconds. 20 */ 21 22void 23__delay(int loops) 24{ 25 int tmp; 26 __asm__ __volatile__( 27 " rpcc %0\n" 28 " addl %1,%0,%1\n" 29 "1: rpcc %0\n" 30 " subl %1,%0,%0\n" 31 " bgt %0,1b" 32 : "=&r" (tmp), "=r" (loops) : "1"(loops)); 33} 34EXPORT_SYMBOL(__delay); 35 36#ifdef CONFIG_SMP 37#define LPJ cpu_data[smp_processor_id()].loops_per_jiffy 38#else 39#define LPJ loops_per_jiffy 40#endif 41 42void 43udelay(unsigned long usecs) 44{ 45 usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ; 46 __delay((long)usecs >> 32); 47} 48EXPORT_SYMBOL(udelay); 49 50void 51ndelay(unsigned long nsecs) 52{ 53 nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ; 54 __delay((long)nsecs >> 32); 55} 56EXPORT_SYMBOL(ndelay);