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Diffstat (limited to 'arch/nios2/kernel/head.S')
| -rw-r--r-- | arch/nios2/kernel/head.S | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/arch/nios2/kernel/head.S b/arch/nios2/kernel/head.S new file mode 100644 index 0000000000..372ce4a330 --- /dev/null +++ b/arch/nios2/kernel/head.S @@ -0,0 +1,175 @@ +/* + * Copyright (C) 2009 Wind River Systems Inc + * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com + * Copyright (C) 2004 Microtronix Datacom Ltd + * Copyright (C) 2001 Vic Phillips, Microtronix Datacom Ltd. + * + * Based on head.S for Altera's Excalibur development board with nios processor + * + * Based on the following from the Excalibur sdk distribution: + * NA_MemoryMap.s, NR_JumpToStart.s, NR_Setup.s, NR_CWPManager.s + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + */ + +#include <linux/init.h> +#include <linux/linkage.h> +#include <asm/thread_info.h> +#include <asm/processor.h> +#include <asm/cache.h> +#include <asm/page.h> +#include <asm/asm-offsets.h> +#include <asm/asm-macros.h> + +/* + * ZERO_PAGE is a special page that is used for zero-initialized + * data and COW. + */ +.data +.global empty_zero_page +.align 12 +empty_zero_page: + .space PAGE_SIZE + +/* + * This global variable is used as an extension to the nios' + * STATUS register to emulate a user/supervisor mode. + */ + .data + .align 2 + .set noat + + .global _current_thread +_current_thread: + .long 0 +/* + * Input(s): passed from u-boot + * r4 - Optional pointer to a board information structure. + * r5 - Optional pointer to the physical starting address of the init RAM + * disk. + * r6 - Optional pointer to the physical ending address of the init RAM + * disk. + * r7 - Optional pointer to the physical starting address of any kernel + * command-line parameters. + */ + +/* + * First executable code - detected and jumped to by the ROM bootstrap + * if the code resides in flash (looks for "Nios" at offset 0x0c from + * the potential executable image). + */ + __HEAD +ENTRY(_start) + wrctl status, r0 /* Disable interrupts */ + + /* Initialize all cache lines within the instruction cache */ + movia r1, NIOS2_ICACHE_SIZE + movui r2, NIOS2_ICACHE_LINE_SIZE + +icache_init: + initi r1 + sub r1, r1, r2 + bgt r1, r0, icache_init + br 1f + + /* + * This is the default location for the exception handler. Code in jump + * to our handler + */ +ENTRY(exception_handler_hook) + movia r24, inthandler + jmp r24 + +ENTRY(fast_handler) + nextpc et +helper: + stw r3, r3save - helper(et) + + rdctl r3 , pteaddr + srli r3, r3, 12 + slli r3, r3, 2 + movia et, pgd_current + + ldw et, 0(et) + add r3, et, r3 + ldw et, 0(r3) + + rdctl r3, pteaddr + andi r3, r3, 0xfff + add et, r3, et + ldw et, 0(et) + wrctl tlbacc, et + nextpc et +helper2: + ldw r3, r3save - helper2(et) + subi ea, ea, 4 + eret +r3save: + .word 0x0 +ENTRY(fast_handler_end) + +1: + /* + * After the instruction cache is initialized, the data cache must + * also be initialized. + */ + movia r1, NIOS2_DCACHE_SIZE + movui r2, NIOS2_DCACHE_LINE_SIZE + +dcache_init: + initd 0(r1) + sub r1, r1, r2 + bgt r1, r0, dcache_init + + nextpc r1 /* Find out where we are */ +chkadr: + movia r2, chkadr + beq r1, r2,finish_move /* We are running in RAM done */ + addi r1, r1,(_start - chkadr) /* Source */ + movia r2, _start /* Destination */ + movia r3, __bss_start /* End of copy */ + +loop_move: /* r1: src, r2: dest, r3: last dest */ + ldw r8, 0(r1) /* load a word from [r1] */ + stw r8, 0(r2) /* store a word to dest [r2] */ + flushd 0(r2) /* Flush cache for safety */ + addi r1, r1, 4 /* inc the src addr */ + addi r2, r2, 4 /* inc the dest addr */ + blt r2, r3, loop_move + + movia r1, finish_move /* VMA(_start)->l1 */ + jmp r1 /* jmp to _start */ + +finish_move: + + /* Mask off all possible interrupts */ + wrctl ienable, r0 + + /* Clear .bss */ + movia r2, __bss_start + movia r1, __bss_stop +1: + stb r0, 0(r2) + addi r2, r2, 1 + bne r1, r2, 1b + + movia r1, init_thread_union /* set stack at top of the task union */ + addi sp, r1, THREAD_SIZE + movia r2, _current_thread /* Remember current thread */ + stw r1, 0(r2) + + movia r1, nios2_boot_init /* save args r4-r7 passed from u-boot */ + callr r1 + + movia r1, start_kernel /* call start_kernel as a subroutine */ + callr r1 + + /* If we return from start_kernel, break to the oci debugger and + * buggered we are. + */ + break + + /* End of startup code */ +.set at |