summaryrefslogtreecommitdiff
path: root/arch/microblaze/cpu/start.S
blob: 9077f742ce20ca47f9cf7099ede8b15fba99d609 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
/*
 * (C) Copyright 2007 Michal Simek
 * (C) Copyright 2004 Atmark Techno, Inc.
 *
 * Michal  SIMEK <monstr@monstr.eu>
 * Yasushi SHOJI <yashi@atmark-techno.com>
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */

#include <asm-offsets.h>
#include <config.h>

	.text
	.global _start
_start:
	/*
	 * reserve registers:
	 * r10: Stores little/big endian offset for vectors
	 * r2: Stores imm opcode
	 * r3: Stores brai opcode
	 */

	mts	rmsr, r0	/* disable cache */
	addi	r1, r0, CONFIG_SYS_INIT_SP_OFFSET
	addi	r1, r1, -4	/* Decrement SP to top of memory */

	/* Find-out if u-boot is running on BIG/LITTLE endian platform
	 * There are some steps which is necessary to keep in mind:
	 * 1. Setup offset value to r6
	 * 2. Store word offset value to address 0x0
	 * 3. Load just byte from address 0x0
	 * 4a) LITTLE endian - r10 contains 0x2 because it is the smallest
	 *     value that's why is on address 0x0
	 * 4b) BIG endian - r10 contains 0x0 because 0x2 offset is on addr 0x3
	 */
	addik	r6, r0, 0x2 /* BIG/LITTLE endian offset */
	lwi	r7, r0, 0x28
	swi	r6, r0, 0x28 /* used first unused MB vector */
	lbui	r10, r0, 0x28 /* used first unused MB vector */
	swi	r7, r0, 0x28

	/* add opcode instruction for 32bit jump - 2 instruction imm & brai */
	addi	r2, r0, 0xb0000000	/* hex b000 opcode imm */
	addi	r3, r0, 0xb8080000	/* hew b808 opcode brai */

#ifdef CONFIG_SYS_RESET_ADDRESS
	/* reset address */
	swi	r2, r0, 0x0	/* reset address - imm opcode */
	swi	r3, r0, 0x4	/* reset address - brai opcode */

	addik	r6, r0, CONFIG_SYS_RESET_ADDRESS
	sw	r6, r1, r0
	lhu	r7, r1, r10
	rsubi	r8, r10, 0x2
	sh	r7, r0, r8
	rsubi	r8, r10, 0x6
	sh	r6, r0, r8
#endif

#ifdef CONFIG_SYS_USR_EXCEP
	/* user_vector_exception */
	swi	r2, r0, 0x8	/* user vector exception - imm opcode */
	swi	r3, r0, 0xC	/* user vector exception - brai opcode */

	addik	r6, r0, _exception_handler
	sw	r6, r1, r0
	/*
	 * BIG ENDIAN memory map for user exception
	 * 0x8: 0xB000XXXX
	 * 0xC: 0xB808XXXX
	 *
	 * then it is necessary to count address for storing the most significant
	 * 16bits from _exception_handler address and copy it to
	 * 0xa address. Big endian use offset in r10=0 that's why is it just
	 * 0xa address. The same is done for the least significant 16 bits
	 * for 0xe address.
	 *
	 * LITTLE ENDIAN memory map for user exception
	 * 0x8: 0xXXXX00B0
	 * 0xC: 0xXXXX08B8
	 *
	 * Offset is for little endian setup to 0x2. rsubi instruction decrease
	 * address value to ensure that points to proper place which is
	 * 0x8 for the most significant 16 bits and
	 * 0xC for the least significant 16 bits
	 */
	lhu	r7, r1, r10
	rsubi	r8, r10, 0xa
	sh	r7, r0, r8
	rsubi	r8, r10, 0xe
	sh	r6, r0, r8
#endif

#ifdef CONFIG_SYS_INTC_0
	/* interrupt_handler */
	swi	r2, r0, 0x10	/* interrupt - imm opcode */
	swi	r3, r0, 0x14	/* interrupt - brai opcode */

	addik	r6, r0, _interrupt_handler
	sw	r6, r1, r0
	lhu	r7, r1, r10
	rsubi	r8, r10, 0x12
	sh	r7, r0, r8
	rsubi	r8, r10, 0x16
	sh	r6, r0, r8
#endif

	/* hardware exception */
	swi	r2, r0, 0x20	/* hardware exception - imm opcode */
	swi	r3, r0, 0x24	/* hardware exception - brai opcode */

	addik	r6, r0, _hw_exception_handler
	sw	r6, r1, r0
	lhu	r7, r1, r10
	rsubi	r8, r10, 0x22
	sh	r7, r0, r8
	rsubi	r8, r10, 0x26
	sh	r6, r0, r8

	/* enable instruction and data cache */
	mfs	r12, rmsr
	ori	r12, r12, 0xa0
	mts	rmsr, r12

clear_bss:
	/* clear BSS segments */
	addi	r5, r0, __bss_start
	addi	r4, r0, __bss_end
	cmp	r6, r5, r4
	beqi	r6, 3f
2:
	swi     r0, r5, 0 /* write zero to loc */
	addi    r5, r5, 4 /* increment to next loc */
	cmp     r6, r5, r4 /* check if we have reach the end */
	bnei    r6, 2b
3:	/* jumping to board_init */
	brai	board_init
1:	bri	1b

/*
 * Read 16bit little endian
 */
	.text
	.global	in16
	.ent	in16
	.align	2
in16:	lhu	r3, r0, r5
	bslli	r4, r3, 8
	bsrli	r3, r3, 8
	andi	r4, r4, 0xffff
	or	r3, r3, r4
	rtsd	r15, 8
	sext16	r3, r3
	.end	in16

/*
 * Write 16bit little endian
 * first parameter(r5) - address, second(r6) - short value
 */
	.text
	.global	out16
	.ent	out16
	.align	2
out16:	bslli	r3, r6, 8
	bsrli	r6, r6, 8
	andi	r3, r3, 0xffff
	or	r3, r3, r6
	sh	r3, r0, r5
	rtsd	r15, 8
	or	r0, r0, r0
	.end	out16