delay.h

来自「u-boot-1.1.6 源码包」· C头文件 代码 · 共 56 行

/*
 * U-boot - delay.h Routines for introducing delays
 *
 * Copyright (c) 2005 blackfin.uclinux.org
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */

#ifndef _BLACKFIN_DELAY_H
#define _BLACKFIN_DELAY_H

/*
 * Changes made by [e-mail], for BLACKFIN
 * Copyright (C) 1994 Hamish Macdonald
 *
 * Delay routines, using a pre-computed "loops_per_second" value.
 */

extern __inline__ void __delay(unsigned long loops)
{
	__asm__ __volatile__("1:\t%0 += -1;\n\t"
				"cc = %0 == 0;\n\t"
				"if ! cc jump 1b;\n":"=d"(loops)
				:"0"(loops));
}

/*
 * 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)
 */
extern __inline__ void udelay(unsigned long usecs)
{
	__delay(usecs);
}

#endif