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      1 /* $NetBSD: timer.c,v 1.1 2025/11/16 20:11:47 jmcneill Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 2025 Jared McNeill <jmcneill (at) invisible.ca>
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #include <lib/libsa/stand.h>
     30 
     31 #include <machine/pio.h>
     32 
     33 #include "timer.h"
     34 
     35 #define	HW_BASE		0x0d800000
     36 #define HW_TIMER	(HW_BASE + 0x010)
     37 
     38 void
     39 timer_udelay(u_int usecs)
     40 {
     41 	uint32_t val, oval;
     42 	int64_t ticks = usecs * 2;	/* Each tick is appx. 526.7ns */
     43 
     44 	val = in32(HW_TIMER);
     45 	while (ticks > 0) {
     46 		int64_t elapsed;
     47 
     48 		oval = val;
     49 		val = in32(HW_TIMER);
     50 		if (val >= oval) {
     51 			elapsed = val - oval;
     52 		} else {
     53 			elapsed = (UINT32_MAX - oval) + val + 1;
     54 		}
     55 		ticks -= elapsed;
     56 	}
     57 }
     58