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Linux/arch/alpha/lib/udelay.c

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  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 
 22 void
 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 }
 34 EXPORT_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 
 42 void
 43 udelay(unsigned long usecs)
 44 {
 45         usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
 46         __delay((long)usecs >> 32);
 47 }
 48 EXPORT_SYMBOL(udelay);
 49 
 50 void
 51 ndelay(unsigned long nsecs)
 52 {
 53         nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
 54         __delay((long)nsecs >> 32);
 55 }
 56 EXPORT_SYMBOL(ndelay);
 57 

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