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/arch/powerpc/boot/util.S

https://github.com/aicjofs/android_kernel_lge_v500_20d_f2fs
Assembly | 88 lines | 83 code | 5 blank | 0 comment | 2 complexity | c9a916825d3f5720333bd6e00c103788 MD5 | raw file
 1/*
 2 * Copied from <file:arch/powerpc/kernel/misc_32.S>
 3 *
 4 * This file contains miscellaneous low-level functions.
 5 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 6 *
 7 * Largely rewritten by Cort Dougan (cort@cs.nmt.edu)
 8 * and Paul Mackerras.
 9 *
10 * kexec bits:
11 * Copyright (C) 2002-2003 Eric Biederman  <ebiederm@xmission.com>
12 * GameCube/ppc32 port Copyright (C) 2004 Albert Herranz
13 *
14 * This program is free software; you can redistribute it and/or
15 * modify it under the terms of the GNU General Public License
16 * as published by the Free Software Foundation; either version
17 * 2 of the License, or (at your option) any later version.
18 *
19 */
20#include "ppc_asm.h"
21
22#define SPRN_PVR        0x11F   /* Processor Version Register */
23
24	.text
25
26/* udelay (on non-601 processors) needs to know the period of the
27 * timebase in nanoseconds.  This used to be hardcoded to be 60ns
28 * (period of 66MHz/4).  Now a variable is used that is initialized to
29 * 60 for backward compatibility, but it can be overridden as necessary
30 * with code something like this:
31 *    extern unsigned long timebase_period_ns;
32 *    timebase_period_ns = 1000000000 / bd->bi_tbfreq;
33 */
34	.data
35	.globl timebase_period_ns
36timebase_period_ns:
37	.long	60
38
39	.text
40/*
41 * Delay for a number of microseconds
42 */
43	.globl	udelay
44udelay:
45	mfspr	r4,SPRN_PVR
46	srwi	r4,r4,16
47	cmpwi	0,r4,1		/* 601 ? */
48	bne	.udelay_not_601
4900:	li	r0,86	/* Instructions / microsecond? */
50	mtctr	r0
5110:	addi	r0,r0,0 /* NOP */
52	bdnz	10b
53	subic.	r3,r3,1
54	bne	00b
55	blr
56
57.udelay_not_601:
58	mulli	r4,r3,1000	/* nanoseconds */
59	/*  Change r4 to be the number of ticks using:
60	 *	(nanoseconds + (timebase_period_ns - 1 )) / timebase_period_ns
61	 *  timebase_period_ns defaults to 60 (16.6MHz) */
62	mflr	r5
63	bl	0f
640:	mflr	r6
65	mtlr	r5
66	lis	r5,0b@ha
67	addi	r5,r5,0b@l
68	subf	r5,r5,r6	/* In case we're relocated */
69	addis	r5,r5,timebase_period_ns@ha
70	lwz	r5,timebase_period_ns@l(r5)
71	add	r4,r4,r5
72	addi	r4,r4,-1
73	divw	r4,r4,r5	/* BUS ticks */
741:	mftbu	r5
75	mftb	r6
76	mftbu	r7
77	cmpw	0,r5,r7
78	bne	1b		/* Get [synced] base time */
79	addc	r9,r6,r4	/* Compute end time */
80	addze	r8,r5
812:	mftbu	r5
82	cmpw	0,r5,r8
83	blt	2b
84	bgt	3f
85	mftb	r6
86	cmpw	0,r6,r9
87	blt	2b
883:	blr