/*
* Copyright (C) 2009 Wind River Systems Inc
* Implemented by [email protected] and [email protected]
* 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
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