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/*
* arch/s390/kernel/delay.c
* Precise Delay Loops for S390
*
* S390 version
* Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
*
* Derived from "arch/i386/lib/delay.c"
* Copyright (C) 1993 Linus Torvalds
* Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
*/
#include <linux/config.h>
#include <linux/sched.h>
#include <linux/delay.h>
#ifdef CONFIG_SMP
#include <asm/smp.h>
#endif
void __delay(unsigned long loops)
{
/*
* To end the bloody studid and useless discussion about the
* BogoMips number I took the liberty to define the __delay
* function in a way that that resulting BogoMips number will
* yield the megahertz number of the cpu. The important function
* is udelay and that is done using the tod clock. -- martin.
*/
__asm__ __volatile__(
"0: brct %0,0b"
: /* no outputs */ : "r" ((loops/2) + 1));
}
/*
* Waits for 'usecs' microseconds using the tod clock, giving up the time slice
* of the virtual PU inbetween to avoid congestion.
*/
void __udelay(unsigned long usecs)
{
uint64_t start_cc, end_cc;
if (usecs == 0)
return;
asm volatile ("STCK %0" : "=m" (start_cc));
do {
cpu_relax();
asm volatile ("STCK %0" : "=m" (end_cc));
} while (((end_cc - start_cc)/4096) < usecs);
}
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