/*      $NetBSD: delay.s,v 1.1 2026/03/28 22:19:33 thorpej Exp $        */

/*
 * Copyright (c) 1988 University of Utah.
 * Copyright (c) 1980, 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * from: Utah $Hdr: locore.s 1.58 91/04/22$
 *
 *      @(#)locore.s    7.11 (Berkeley) 5/9/91
 */

#include <machine/asm.h>

#include "assym.h"

        .file   "delay.s"
        .text

/*
 * delay(unsigned int N)
 *
 * Delay for at least N microseconds.
 * This routine depends on the variable:  delay_divisor
 * which should be set based on the CPU clock rate
 * (either a known pre-computed value for a given machine
 * type or calibrated against a known clock source).
 */
ENTRY_NOPROFILE(delay)
        movl    4(%sp),%d0              | %d0 = arg = usecs
#ifdef DIAGNOSTIC
        cmpl    #DELAY_MAXVAL,%d0       | exceeds max value?
        bgt     3f                      | yes, go panic.
#endif
        moveq   #DELAY_MAGSHIFT,%d1     | magnification factor
        lsll    %d1,%d0

        | %d1 = delay_divisor;
        movl    _C_LABEL(delay_divisor),%d1

        jra     2f                      /* Jump into the loop! */

        /*
         * Align the branch target of the loop to a half-line (8-byte)
         * boundary to minimize cache effects.  This guarantees both
         * that there will be no prefetch stalls due to cache line burst
         * operations and that the loop will run from a single cache
         * half-line.
         */
        .align  8
2:      subl    %d1,%d0
        bgt     2b
        rts
#ifdef DIAGNOSTIC
3:
        pea     Ldelaypanicmsg
        jbsr    _C_LABEL(panic)
        rts
Ldelaypanicmsg:
        .asciz  "delay exceeds max value"
        .even
#endif