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