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Diffstat (limited to 'cpu/nios/start.S')
| -rw-r--r-- | cpu/nios/start.S | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/cpu/nios/start.S b/cpu/nios/start.S new file mode 100644 index 0000000..7cbd1a7 --- /dev/null +++ b/cpu/nios/start.S @@ -0,0 +1,186 @@ +/* + * (C) Copyright 2003, 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> + +#if !defined(CONFIG_IDENT_STRING) +#define CONFIG_IDENT_STRING "" +#endif + +#define STATUS_INIT 0x8600 /* IE=1, IPRI=2 */ + +/************************************************************************* + * RESTART + ************************************************************************/ + + .text + .global _start + +_start: + bsr 0f + nop + .long _start + + /* GERMS -- The "standard-32" configuration GERMS monitor looks + * for the string "Nios" at flash_base + 0xc (actually it only + * tests for 'N', 'i'). You can leave support for this in place + * as it's only a few words. + */ + . = _start + 0x000c + .string "Nios" + + .align 4 +0: + /* + * Early setup -- set cwp = HI_LIMIT, IPRI = 2, IE = 1 to + * enable underflow exceptions. Disable cache. + * NOTE: %o7 has return addr -- save in %g7 use later. + */ + mov %g7, %o7 + + pfx 2 /* WVALID */ + rdctl %g0 + lsri %g0, 1 + pfx %hi(STATUS_INIT) + or %g0, %lo(STATUS_INIT) + wrctl %g0 /* update status */ + nop + + /* + * STACK + */ + pfx %hi(CFG_INIT_SP) + movi %sp, %lo(CFG_INIT_SP) + pfx %xhi(CFG_INIT_SP) + movhi %sp, %xlo(CFG_INIT_SP) + mov %fp, %sp + + pfx %hi(4*16) + subi %sp, %lo(4*16) /* Space for reg window mgmt */ + + /* + * RELOCATE -- %g7 has return addr from bsr at _start. + */ + pfx %hi(__u_boot_cmd_end) + movi %g5, %lo(__u_boot_cmd_end) + pfx %xhi(__u_boot_cmd_end) + movhi %g5, %xlo(__u_boot_cmd_end) /* %g5 <- end address */ + + lsli %g7, 1 /* mem = retaddr << 1 */ + mov %g6, %g7 + subi %g6, 4 /* %g6 <- src addr */ + ld %g7, [%g7] /* %g7 <- dst addr */ + +1: cmp %g7, %g5 + skps cc_nz + br 2f + nop /* delay slot */ + + ld %g0, [%g6] + addi %g6, 4 /* src++ */ + st [%g7], %g0 + addi %g7, 4 /* dst++ */ + br 1b + nop /* delay slot */ +2: + + /* + * Jump to relocation address + */ + pfx %hi(reloc@h) + movi %g0, %lo(reloc@h) + pfx %xhi(reloc@h) + movhi %g0, %xlo(reloc@h) + jmp %g0 +reloc: + + /* + * CLEAR BSS + */ + pfx %hi(__bss_end) + movi %g5, %lo(__bss_end) + pfx %xhi(__bss_end) + movhi %g5, %xlo(__bss_end) /* %g5 <- end address */ + pfx %hi(__bss_start) + movi %g7, %lo(__bss_start) + pfx %xhi(__bss_start) + movhi %g7, %xlo(__bss_start) /* %g7 <- end address */ + + movi %g0, 0 +3: cmp %g7, %g5 + skps cc_nz + br 4f + nop /* delay slot */ + + st [%g7], %g0 + addi %g7, 4 /* (delay slot) dst++ */ + br 3b + nop /* delay slot */ +4: + + /* + * Call board_init -- never returns + */ + pfx %hi(board_init@h) + movi %g1, %lo(board_init@h) + pfx %xhi(board_init@h) + movhi %g1, %xlo(board_init@h) + call %g1 + nop /* Delaly slot */ + /* NEVER RETURNS */ + +/* + * dly_clks -- Nios doesn't have a time/clk reference for simple + * delay loops, so we do our best by counting instruction cycles. + * A control register that counts system clock cycles would be + * a handy feature -- hint for Altera ;-) + */ + .globl dly_clks + /* Each loop is 4 instructions as delay slot is always + * executed. Each instruction is approximately 4 clocks + * (according to some lame info from Altera). So ... + * ... each loop is about 16 clocks. + */ + +dly_clks: + lsri %o0, 4 /* cnt/16 */ + +8: skprnz %o0 + br 9f + subi %o0, 1 /* cnt--, Delay slot */ + br 8b + nop + +9: lret + nop /* Delay slot */ + + + .data + .globl version_string + +version_string: + .ascii U_BOOT_VERSION + .ascii " (", __DATE__, " - ", __TIME__, ")" + .ascii CONFIG_IDENT_STRING, "\0" |