linux_kernel/arch/mips/lib/delay.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1994 by Waldorf Electronics
 * Copyright (C) 1995 - 2000, 01, 03 by Ralf Baechle
 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
 * Copyright (C) 2007, 2014 Maciej W. Rozycki
 */
#include <linux/module.h>
#include <linux/param.h>
#include <linux/smp.h>

#include <asm/compiler.h>
#include <asm/war.h>

#ifndef CONFIG_CPU_DADDI_WORKAROUNDS
#define GCC_DADDI_IMM_ASM() "I"
#else
#define GCC_DADDI_IMM_ASM() "r"
#endif

void __delay(unsigned long loops)
{
	__asm__ __volatile__ (
	"	.set	noreorder				\n"
	"	.align	3					\n"
	"1:	bnez	%0, 1b					\n"
#if BITS_PER_LONG == 32
	"	subu	%0, %1					\n"
#else
	"	dsubu	%0, %1					\n"
#endif
	"	.set	reorder					\n"
	: "=r" (loops)
	: GCC_DADDI_IMM_ASM() (1), "0" (loops));
}
EXPORT_SYMBOL(__delay);

/*
 * Division by multiplication: you don't have to worry about
 * loss of precision.
 *
 * Use only for very small delays ( < 1 msec).	Should probably use a
 * lookup table, really, as the multiplications take much too long with
 * short delays.  This is a "reasonable" implementation, though (and the
 * first constant multiplications gets optimized away if the delay is
 * a constant)
 */

void __udelay(unsigned long us)
{
	unsigned int lpj = raw_current_cpu_data.udelay_val;

	__delay((us * 0x000010c7ull * HZ * lpj) >> 32);
}
EXPORT_SYMBOL(__udelay);

void __ndelay(unsigned long ns)
{
	unsigned int lpj = raw_current_cpu_data.udelay_val;

	__delay((ns * 0x00000005ull * HZ * lpj) >> 32);
}
EXPORT_SYMBOL(__ndelay);