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5c952cf0 WD |
1 | /* |
2 | * (C) Copyright 2004, Psyent Corporation <www.psyent.com> | |
3 | * Scott McNutt <smcnutt@psyent.com> | |
4 | * | |
1a459660 | 5 | * SPDX-License-Identifier: GPL-2.0+ |
5c952cf0 WD |
6 | */ |
7 | ||
25ddd1fb | 8 | #include <asm-offsets.h> |
5c952cf0 WD |
9 | #include <config.h> |
10 | #include <version.h> | |
11 | ||
12 | /************************************************************************* | |
13 | * RESTART | |
14 | ************************************************************************/ | |
15 | ||
16 | .text | |
17 | .global _start | |
18 | ||
19 | _start: | |
fd2712d0 | 20 | wrctl status, r0 /* Disable interrupts */ |
5c952cf0 WD |
21 | /* ICACHE INIT -- only the icache line at the reset address |
22 | * is invalidated at reset. So the init must stay within | |
23 | * the cache line size (8 words). If GERMS is used, we'll | |
24 | * just be invalidating the cache a second time. If cache | |
25 | * is not implemented initi behaves as nop. | |
26 | */ | |
6d0f6bcf JCPV |
27 | ori r4, r0, %lo(CONFIG_SYS_ICACHELINE_SIZE) |
28 | movhi r5, %hi(CONFIG_SYS_ICACHE_SIZE) | |
29 | ori r5, r5, %lo(CONFIG_SYS_ICACHE_SIZE) | |
fd2712d0 TC |
30 | 0: initi r5 |
31 | sub r5, r5, r4 | |
32 | bgt r5, r0, 0b | |
0c1c117c WD |
33 | br _except_end /* Skip the tramp */ |
34 | ||
35 | /* EXCEPTION TRAMPOLINE -- the following gets copied | |
36 | * to the exception address (below), but is otherwise at the | |
37 | * default exception vector offset (0x0020). | |
38 | */ | |
39 | _except_start: | |
40 | movhi et, %hi(_exception) | |
41 | ori et, et, %lo(_exception) | |
42 | jmp et | |
43 | _except_end: | |
5c952cf0 WD |
44 | |
45 | /* INTERRUPTS -- for now, all interrupts masked and globally | |
46 | * disabled. | |
47 | */ | |
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48 | wrctl ienable, r0 /* All disabled */ |
49 | ||
50 | /* DCACHE INIT -- if dcache not implemented, initd behaves as | |
51 | * nop. | |
52 | */ | |
6d0f6bcf JCPV |
53 | movhi r4, %hi(CONFIG_SYS_DCACHELINE_SIZE) |
54 | ori r4, r4, %lo(CONFIG_SYS_DCACHELINE_SIZE) | |
55 | movhi r5, %hi(CONFIG_SYS_DCACHE_SIZE) | |
56 | ori r5, r5, %lo(CONFIG_SYS_DCACHE_SIZE) | |
5c952cf0 WD |
57 | mov r6, r0 |
58 | 1: initd 0(r6) | |
59 | add r6, r6, r4 | |
60 | bltu r6, r5, 1b | |
61 | ||
62 | /* RELOCATE CODE, DATA & COMMAND TABLE -- the following code | |
63 | * assumes code, data and the command table are all | |
64 | * contiguous. This lets us relocate everything as a single | |
65 | * block. Make sure the linker script matches this ;-) | |
66 | */ | |
67 | nextpc r4 | |
68 | _cur: movhi r5, %hi(_cur - _start) | |
69 | ori r5, r5, %lo(_cur - _start) | |
70 | sub r4, r4, r5 /* r4 <- cur _start */ | |
71 | mov r8, r4 | |
72 | movhi r5, %hi(_start) | |
73 | ori r5, r5, %lo(_start) /* r5 <- linked _start */ | |
74 | beq r4, r5, 3f | |
75 | ||
76 | movhi r6, %hi(_edata) | |
77 | ori r6, r6, %lo(_edata) | |
78 | 2: ldwio r7, 0(r4) | |
79 | addi r4, r4, 4 | |
80 | stwio r7, 0(r5) | |
81 | addi r5, r5, 4 | |
82 | bne r5, r6, 2b | |
83 | 3: | |
84 | ||
85 | /* ZERO BSS/SBSS -- bss and sbss are assumed to be adjacent | |
3929fb0a | 86 | * and between __bss_start and __bss_end. |
5c952cf0 WD |
87 | */ |
88 | movhi r5, %hi(__bss_start) | |
89 | ori r5, r5, %lo(__bss_start) | |
3929fb0a SG |
90 | movhi r6, %hi(__bss_end) |
91 | ori r6, r6, %lo(__bss_end) | |
5c952cf0 WD |
92 | beq r5, r6, 5f |
93 | ||
94 | 4: stwio r0, 0(r5) | |
95 | addi r5, r5, 4 | |
96 | bne r5, r6, 4b | |
97 | 5: | |
98 | ||
5c952cf0 WD |
99 | /* JUMP TO RELOC ADDR */ |
100 | movhi r4, %hi(_reloc) | |
101 | ori r4, r4, %lo(_reloc) | |
102 | jmp r4 | |
103 | _reloc: | |
104 | ||
105 | /* COPY EXCEPTION TRAMPOLINE -- copy the tramp to the | |
0c1c117c WD |
106 | * exception address. Define CONFIG_ROM_STUBS to prevent |
107 | * the copy (e.g. exception in flash or in other | |
108 | * softare/firmware component). | |
5c952cf0 WD |
109 | */ |
110 | #if !defined(CONFIG_ROM_STUBS) | |
111 | movhi r4, %hi(_except_start) | |
112 | ori r4, r4, %lo(_except_start) | |
113 | movhi r5, %hi(_except_end) | |
114 | ori r5, r5, %lo(_except_end) | |
6d0f6bcf JCPV |
115 | movhi r6, %hi(CONFIG_SYS_EXCEPTION_ADDR) |
116 | ori r6, r6, %lo(CONFIG_SYS_EXCEPTION_ADDR) | |
0c1c117c | 117 | beq r4, r6, 7f /* Skip if at proper addr */ |
5c952cf0 WD |
118 | |
119 | 6: ldwio r7, 0(r4) | |
120 | stwio r7, 0(r6) | |
121 | addi r4, r4, 4 | |
122 | addi r6, r6, 4 | |
123 | bne r4, r5, 6b | |
0c1c117c | 124 | 7: |
5c952cf0 WD |
125 | #endif |
126 | ||
127 | /* STACK INIT -- zero top two words for call back chain. | |
128 | */ | |
6d0f6bcf JCPV |
129 | movhi sp, %hi(CONFIG_SYS_INIT_SP) |
130 | ori sp, sp, %lo(CONFIG_SYS_INIT_SP) | |
5c952cf0 WD |
131 | addi sp, sp, -8 |
132 | stw r0, 0(sp) | |
133 | stw r0, 4(sp) | |
134 | mov fp, sp | |
135 | ||
136 | /* | |
137 | * Call board_init -- never returns | |
138 | */ | |
139 | movhi r4, %hi(board_init@h) | |
140 | ori r4, r4, %lo(board_init@h) | |
141 | callr r4 | |
142 | ||
143 | /* NEVER RETURNS -- but branch to the _start just | |
144 | * in case ;-) | |
145 | */ | |
146 | br _start | |
147 | ||
5c952cf0 WD |
148 | |
149 | /* | |
150 | * dly_clks -- Nios2 (like Nios1) doesn't have a timebase in | |
151 | * the core. For simple delay loops, we do our best by counting | |
152 | * instruction cycles. | |
153 | * | |
154 | * Instruction performance varies based on the core. For cores | |
155 | * with icache and static/dynamic branch prediction (II/f, II/s): | |
156 | * | |
53677ef1 WD |
157 | * Normal ALU (e.g. add, cmp, etc): 1 cycle |
158 | * Branch (correctly predicted, taken): 2 cycles | |
5c952cf0 WD |
159 | * Negative offset is predicted (II/s). |
160 | * | |
161 | * For cores without icache and no branch prediction (II/e): | |
162 | * | |
53677ef1 WD |
163 | * Normal ALU (e.g. add, cmp, etc): 6 cycles |
164 | * Branch (no prediction): 6 cycles | |
5c952cf0 WD |
165 | * |
166 | * For simplicity, if an instruction cache is implemented we | |
167 | * assume II/f or II/s. Otherwise, we use the II/e. | |
168 | * | |
169 | */ | |
53677ef1 | 170 | .globl dly_clks |
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171 | |
172 | dly_clks: | |
173 | ||
6d0f6bcf | 174 | #if (CONFIG_SYS_ICACHE_SIZE > 0) |
5c952cf0 WD |
175 | subi r4, r4, 3 /* 3 clocks/loop */ |
176 | #else | |
177 | subi r4, r4, 12 /* 12 clocks/loop */ | |
178 | #endif | |
179 | bge r4, r0, dly_clks | |
180 | ret | |
181 | ||
5c952cf0 WD |
182 | .data |
183 | .globl version_string | |
184 | ||
185 | version_string: | |
09c2e90c | 186 | .ascii U_BOOT_VERSION_STRING, "\0" |