/* * (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(CFG_ICACHELINE_SIZE) movhi r5, %hi(CFG_ICACHE_SIZE) ori r5, r5, %lo(CFG_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(CFG_DCACHELINE_SIZE) ori r4, r4, %lo(CFG_DCACHELINE_SIZE) movhi r5, %hi(CFG_DCACHE_SIZE) ori r5, r5, %lo(CFG_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(CFG_EXCEPTION_ADDR) ori r6, r6, %lo(CFG_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(CFG_INIT_SP) ori sp, sp, %lo(CFG_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 (CFG_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"