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
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
|
/*
* (C) Copyright 2004, Psyent Corporation <www.psyent.com>
* Scott McNutt <smcnutt@psyent.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 <config.h>
#include <version.h>
/*************************************************************************
* RESTART
************************************************************************/
.text
.global _start
_start:
/* ICACHE INIT -- only the icache line at the reset address
* is invalidated at reset. So the init must stay within
* the cache line size (8 words). If GERMS is used, we'll
* just be invalidating the cache a second time. If cache
* is not implemented initi behaves as nop.
*/
ori r4, r0, %lo(CONFIG_SYS_ICACHELINE_SIZE)
movhi r5, %hi(CONFIG_SYS_ICACHE_SIZE)
ori r5, r5, %lo(CONFIG_SYS_ICACHE_SIZE)
mov r6, r0
0: initi r6
add r6, r6, r4
bltu r6, r5, 0b
br _except_end /* Skip the tramp */
/* EXCEPTION TRAMPOLINE -- the following gets copied
* to the exception address (below), but is otherwise at the
* default exception vector offset (0x0020).
*/
_except_start:
movhi et, %hi(_exception)
ori et, et, %lo(_exception)
jmp et
_except_end:
/* INTERRUPTS -- for now, all interrupts masked and globally
* disabled.
*/
wrctl status, r0 /* Disable interrupts */
wrctl ienable, r0 /* All disabled */
/* DCACHE INIT -- if dcache not implemented, initd behaves as
* nop.
*/
movhi r4, %hi(CONFIG_SYS_DCACHELINE_SIZE)
ori r4, r4, %lo(CONFIG_SYS_DCACHELINE_SIZE)
movhi r5, %hi(CONFIG_SYS_DCACHE_SIZE)
ori r5, r5, %lo(CONFIG_SYS_DCACHE_SIZE)
mov r6, r0
1: initd 0(r6)
add r6, r6, r4
bltu r6, r5, 1b
/* RELOCATE CODE, DATA & COMMAND TABLE -- the following code
* assumes code, data and the command table are all
* contiguous. This lets us relocate everything as a single
* block. Make sure the linker script matches this ;-)
*/
nextpc r4
_cur: movhi r5, %hi(_cur - _start)
ori r5, r5, %lo(_cur - _start)
sub r4, r4, r5 /* r4 <- cur _start */
mov r8, r4
movhi r5, %hi(_start)
ori r5, r5, %lo(_start) /* r5 <- linked _start */
beq r4, r5, 3f
movhi r6, %hi(_edata)
ori r6, r6, %lo(_edata)
2: ldwio r7, 0(r4)
addi r4, r4, 4
stwio r7, 0(r5)
addi r5, r5, 4
bne r5, r6, 2b
3:
/* ZERO BSS/SBSS -- bss and sbss are assumed to be adjacent
* and between __bss_start and _end.
*/
movhi r5, %hi(__bss_start)
ori r5, r5, %lo(__bss_start)
movhi r6, %hi(_end)
ori r6, r6, %lo(_end)
beq r5, r6, 5f
4: stwio r0, 0(r5)
addi r5, r5, 4
bne r5, r6, 4b
5:
/* GLOBAL POINTER -- the global pointer is used to reference
* "small data" (see -G switch). The linker script must
* provide the gp address.
*/
movhi gp, %hi(_gp)
ori gp, gp, %lo(_gp)
/* JUMP TO RELOC ADDR */
movhi r4, %hi(_reloc)
ori r4, r4, %lo(_reloc)
jmp r4
_reloc:
/* COPY EXCEPTION TRAMPOLINE -- copy the tramp to the
* exception address. Define CONFIG_ROM_STUBS to prevent
* the copy (e.g. exception in flash or in other
* softare/firmware component).
*/
#if !defined(CONFIG_ROM_STUBS)
movhi r4, %hi(_except_start)
ori r4, r4, %lo(_except_start)
movhi r5, %hi(_except_end)
ori r5, r5, %lo(_except_end)
movhi r6, %hi(CONFIG_SYS_EXCEPTION_ADDR)
ori r6, r6, %lo(CONFIG_SYS_EXCEPTION_ADDR)
beq r4, r6, 7f /* Skip if at proper addr */
6: ldwio r7, 0(r4)
stwio r7, 0(r6)
addi r4, r4, 4
addi r6, r6, 4
bne r4, r5, 6b
7:
#endif
/* STACK INIT -- zero top two words for call back chain.
*/
movhi sp, %hi(CONFIG_SYS_INIT_SP)
ori sp, sp, %lo(CONFIG_SYS_INIT_SP)
addi sp, sp, -8
stw r0, 0(sp)
stw r0, 4(sp)
mov fp, sp
/*
* Call board_init -- never returns
*/
movhi r4, %hi(board_init@h)
ori r4, r4, %lo(board_init@h)
callr r4
/* NEVER RETURNS -- but branch to the _start just
* in case ;-)
*/
br _start
/*
* dly_clks -- Nios2 (like Nios1) doesn't have a timebase in
* the core. For simple delay loops, we do our best by counting
* instruction cycles.
*
* Instruction performance varies based on the core. For cores
* with icache and static/dynamic branch prediction (II/f, II/s):
*
* Normal ALU (e.g. add, cmp, etc): 1 cycle
* Branch (correctly predicted, taken): 2 cycles
* Negative offset is predicted (II/s).
*
* For cores without icache and no branch prediction (II/e):
*
* Normal ALU (e.g. add, cmp, etc): 6 cycles
* Branch (no prediction): 6 cycles
*
* For simplicity, if an instruction cache is implemented we
* assume II/f or II/s. Otherwise, we use the II/e.
*
*/
.globl dly_clks
dly_clks:
#if (CONFIG_SYS_ICACHE_SIZE > 0)
subi r4, r4, 3 /* 3 clocks/loop */
#else
subi r4, r4, 12 /* 12 clocks/loop */
#endif
bge r4, r0, dly_clks
ret
#if !defined(CONFIG_IDENT_STRING)
#define CONFIG_IDENT_STRING ""
#endif
.data
.globl version_string
version_string:
.ascii U_BOOT_VERSION
.ascii " (", __DATE__, " - ", __TIME__, ")"
.ascii CONFIG_IDENT_STRING, "\0"
|
