1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * Copied from <file:arch/powerpc/kernel/misc_32.S>
4 *
5 * This file contains miscellaneous low-level functions.
6 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
7 *
8 * Largely rewritten by Cort Dougan (cort@cs.nmt.edu)
9 * and Paul Mackerras.
10 *
11 * kexec bits:
12 * Copyright (C) 2002-2003 Eric Biederman  <ebiederm@xmission.com>
13 * GameCube/ppc32 port Copyright (C) 2004 Albert Herranz
14 */
15#include "ppc_asm.h"
16
17#define SPRN_PVR        0x11F   /* Processor Version Register */
18
19	.text
20
21/* udelay needs to know the period of the
22 * timebase in nanoseconds.  This used to be hardcoded to be 60ns
23 * (period of 66MHz/4).  Now a variable is used that is initialized to
24 * 60 for backward compatibility, but it can be overridden as necessary
25 * with code something like this:
26 *    extern unsigned long timebase_period_ns;
27 *    timebase_period_ns = 1000000000 / bd->bi_tbfreq;
28 */
29	.data
30	.globl timebase_period_ns
31timebase_period_ns:
32	.long	60
33
34	.text
35/*
36 * Delay for a number of microseconds
37 */
38	.globl	udelay
39udelay:
40	mulli	r4,r3,1000	/* nanoseconds */
41	/*  Change r4 to be the number of ticks using:
42	 *	(nanoseconds + (timebase_period_ns - 1 )) / timebase_period_ns
43	 *  timebase_period_ns defaults to 60 (16.6MHz) */
44	mflr	r5
45	bcl	20,31,0f
460:	mflr	r6
47	mtlr	r5
48	addis	r5,r6,(timebase_period_ns-0b)@ha
49	lwz	r5,(timebase_period_ns-0b)@l(r5)
50	add	r4,r4,r5
51	addi	r4,r4,-1
52	divw	r4,r4,r5	/* BUS ticks */
531:	MFTBU(r5)
54	MFTBL(r6)
55	MFTBU(r7)
56	cmpw	0,r5,r7
57	bne	1b		/* Get [synced] base time */
58	addc	r9,r6,r4	/* Compute end time */
59	addze	r8,r5
602:	MFTBU(r5)
61	cmpw	0,r5,r8
62	blt	2b
63	bgt	3f
64	MFTBL(r6)
65	cmpw	0,r6,r9
66	blt	2b
673:	blr
68