timer.c revision 1.1 
1/* $NetBSD: timer.c,v 1.1 2025/11/16 20:11:47 jmcneill Exp $ */
2
3/*-
4 * Copyright (c) 2025 Jared McNeill <jmcneill@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
38void
39timer_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