1 /* 2 * (C) Copyright 2004, Psyent Corporation <www.psyent.com> 3 * Scott McNutt <smcnutt@psyent.com> 4 * 5 * See file CREDITS for list of people who contributed to this 6 * project. 7 * 8 * This program is free software; you can redistribute it and/or 9 * modify it under the terms of the GNU General Public License as 10 * published by the Free Software Foundation; either version 2 of 11 * the License, or (at your option) any later version. 12 * 13 * This program is distributed in the hope that it will be useful, 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 * GNU General Public License for more details. 17 * 18 * You should have received a copy of the GNU General Public License 19 * along with this program; if not, write to the Free Software 20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, 21 * MA 02111-1307 USA 22 */ 23 24 #include <asm-offsets.h> 25 #include <config.h> 26 #include <version.h> 27 28 /************************************************************************* 29 * RESTART 30 ************************************************************************/ 31 32 .text 33 .global _start 34 35 _start: 36 wrctl status, r0 /* Disable interrupts */ 37 /* ICACHE INIT -- only the icache line at the reset address 38 * is invalidated at reset. So the init must stay within 39 * the cache line size (8 words). If GERMS is used, we'll 40 * just be invalidating the cache a second time. If cache 41 * is not implemented initi behaves as nop. 42 */ 43 ori r4, r0, %lo(CONFIG_SYS_ICACHELINE_SIZE) 44 movhi r5, %hi(CONFIG_SYS_ICACHE_SIZE) 45 ori r5, r5, %lo(CONFIG_SYS_ICACHE_SIZE) 46 0: initi r5 47 sub r5, r5, r4 48 bgt r5, r0, 0b 49 br _except_end /* Skip the tramp */ 50 51 /* EXCEPTION TRAMPOLINE -- the following gets copied 52 * to the exception address (below), but is otherwise at the 53 * default exception vector offset (0x0020). 54 */ 55 _except_start: 56 movhi et, %hi(_exception) 57 ori et, et, %lo(_exception) 58 jmp et 59 _except_end: 60 61 /* INTERRUPTS -- for now, all interrupts masked and globally 62 * disabled. 63 */ 64 wrctl ienable, r0 /* All disabled */ 65 66 /* DCACHE INIT -- if dcache not implemented, initd behaves as 67 * nop. 68 */ 69 movhi r4, %hi(CONFIG_SYS_DCACHELINE_SIZE) 70 ori r4, r4, %lo(CONFIG_SYS_DCACHELINE_SIZE) 71 movhi r5, %hi(CONFIG_SYS_DCACHE_SIZE) 72 ori r5, r5, %lo(CONFIG_SYS_DCACHE_SIZE) 73 mov r6, r0 74 1: initd 0(r6) 75 add r6, r6, r4 76 bltu r6, r5, 1b 77 78 /* RELOCATE CODE, DATA & COMMAND TABLE -- the following code 79 * assumes code, data and the command table are all 80 * contiguous. This lets us relocate everything as a single 81 * block. Make sure the linker script matches this ;-) 82 */ 83 nextpc r4 84 _cur: movhi r5, %hi(_cur - _start) 85 ori r5, r5, %lo(_cur - _start) 86 sub r4, r4, r5 /* r4 <- cur _start */ 87 mov r8, r4 88 movhi r5, %hi(_start) 89 ori r5, r5, %lo(_start) /* r5 <- linked _start */ 90 beq r4, r5, 3f 91 92 movhi r6, %hi(_edata) 93 ori r6, r6, %lo(_edata) 94 2: ldwio r7, 0(r4) 95 addi r4, r4, 4 96 stwio r7, 0(r5) 97 addi r5, r5, 4 98 bne r5, r6, 2b 99 3: 100 101 /* ZERO BSS/SBSS -- bss and sbss are assumed to be adjacent 102 * and between __bss_start and __bss_end__. 103 */ 104 movhi r5, %hi(__bss_start) 105 ori r5, r5, %lo(__bss_start) 106 movhi r6, %hi(__bss_end__) 107 ori r6, r6, %lo(__bss_end__) 108 beq r5, r6, 5f 109 110 4: stwio r0, 0(r5) 111 addi r5, r5, 4 112 bne r5, r6, 4b 113 5: 114 115 /* JUMP TO RELOC ADDR */ 116 movhi r4, %hi(_reloc) 117 ori r4, r4, %lo(_reloc) 118 jmp r4 119 _reloc: 120 121 /* COPY EXCEPTION TRAMPOLINE -- copy the tramp to the 122 * exception address. Define CONFIG_ROM_STUBS to prevent 123 * the copy (e.g. exception in flash or in other 124 * softare/firmware component). 125 */ 126 #if !defined(CONFIG_ROM_STUBS) 127 movhi r4, %hi(_except_start) 128 ori r4, r4, %lo(_except_start) 129 movhi r5, %hi(_except_end) 130 ori r5, r5, %lo(_except_end) 131 movhi r6, %hi(CONFIG_SYS_EXCEPTION_ADDR) 132 ori r6, r6, %lo(CONFIG_SYS_EXCEPTION_ADDR) 133 beq r4, r6, 7f /* Skip if at proper addr */ 134 135 6: ldwio r7, 0(r4) 136 stwio r7, 0(r6) 137 addi r4, r4, 4 138 addi r6, r6, 4 139 bne r4, r5, 6b 140 7: 141 #endif 142 143 /* STACK INIT -- zero top two words for call back chain. 144 */ 145 movhi sp, %hi(CONFIG_SYS_INIT_SP) 146 ori sp, sp, %lo(CONFIG_SYS_INIT_SP) 147 addi sp, sp, -8 148 stw r0, 0(sp) 149 stw r0, 4(sp) 150 mov fp, sp 151 152 /* 153 * Call board_init -- never returns 154 */ 155 movhi r4, %hi(board_init@h) 156 ori r4, r4, %lo(board_init@h) 157 callr r4 158 159 /* NEVER RETURNS -- but branch to the _start just 160 * in case ;-) 161 */ 162 br _start 163 164 165 /* 166 * dly_clks -- Nios2 (like Nios1) doesn't have a timebase in 167 * the core. For simple delay loops, we do our best by counting 168 * instruction cycles. 169 * 170 * Instruction performance varies based on the core. For cores 171 * with icache and static/dynamic branch prediction (II/f, II/s): 172 * 173 * Normal ALU (e.g. add, cmp, etc): 1 cycle 174 * Branch (correctly predicted, taken): 2 cycles 175 * Negative offset is predicted (II/s). 176 * 177 * For cores without icache and no branch prediction (II/e): 178 * 179 * Normal ALU (e.g. add, cmp, etc): 6 cycles 180 * Branch (no prediction): 6 cycles 181 * 182 * For simplicity, if an instruction cache is implemented we 183 * assume II/f or II/s. Otherwise, we use the II/e. 184 * 185 */ 186 .globl dly_clks 187 188 dly_clks: 189 190 #if (CONFIG_SYS_ICACHE_SIZE > 0) 191 subi r4, r4, 3 /* 3 clocks/loop */ 192 #else 193 subi r4, r4, 12 /* 12 clocks/loop */ 194 #endif 195 bge r4, r0, dly_clks 196 ret 197 198 .data 199 .globl version_string 200 201 version_string: 202 .ascii U_BOOT_VERSION_STRING, "\0" 203