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