head.s

ucos mips linux 光盘所得

/*
 * init.S
 *
 * Initialization code for JzRISC.
 *
 * Author: Seeger Chin
 * e-mail: [e-mail]
 *
 * Copyright (C) 2006 Ingenic Semiconductor Inc.
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include <mips.h>

	.text

	.extern c_main

	.global	_start
	.type	_start,@function
	.set	noreorder
	.set	noat
_start:
	la	ra, _start
	//----------------------------------------------------
	// init cp0 registers.
	//----------------------------------------------------
	mtc0	zero, C0_WATCHLO
	mtc0	zero, C0_WATCHHI

	li	t0, 0x0040FC00
	mtc0	t0, C0_STATUS

	li	t1, 0x00800000
	mtc0	t1, C0_CAUSE

	//----------------------------------------------------
	// init caches, assumes a 4way*128set*32byte i/d cache
	//----------------------------------------------------
	li	t0, 3		// enable cache for kseg0 accesses
	mtc0	t0, $16		// CONFIG reg
	la	t0, 0x80000000	// an idx op should use a unmappable address
	ori	t1, t0, 0x4000	// 16kB cache
	mtc0	zero, $28	// TAGLO reg
	mtc0	zero, $29	// TAGHI reg

_init_cache_loop:	
	cache	0x8, 0(t0)	// index store icache tag
	cache	0x9, 0(t0)	// index store dcache tag
	bne	t0, t1, _init_cache_loop
	addiu	t0, t0, 0x20	// 32 bytes per cache line
	nop

	//----------------------------------------------------
	// Invalidate BTB
	//----------------------------------------------------
	mfc0	t0, C0_CONFIG, 7
	nop
	ori	t0, 2
	mtc0	t0, C0_CONFIG, 7
	nop

	//----------------------------------------------------
	// clear BSS section
	//----------------------------------------------------
	la	t0, _fbss
	la	t1, _end
1:	sw	zero, 0(t0)
	bne	t0, t1, 1b
	addiu	t0, 4

	//----------------------------------------------------
	// setup stack and GP, jump to C code
	//----------------------------------------------------
	la	gp, _gp
	la	sp, g_stack
	addiu	sp, sp, 0x2000

	la	t0, c_main
	jr	t0
	nop

	.extern real_exception_entry
	.global except_common_entry
	.type	except_common_entry,@function
except_common_entry:
	la	k0, real_exception_entry
	jr	k0
	nop
	nop
	nop

	.extern UCOS_INTHandler
	.extern exception_handler
	.global real_exception_entry
	.type	real_exception_entry,@function
	.set noreorder
real_exception_entry:
	la	k1, (0x1f << 2)
	mfc0	k0, C0_CAUSE
	and	k0, k0, k1
	beq	zero, k0, intr_handler
	nop
	la	k0, exception_handler
	jr	k0
	nop
intr_handler:
	la	k0, UCOS_INTHandler
	jr	k0
	nop
	.set reorder

	.global exception_handler
	.type	exception_handler,@function
	.set noreorder
exception_handler:
	la	sp, g_stack		// restore the SP register, and we
	addiu	sp, sp, 0x1000		// will panic in except handler.
	sw	$0, (4*0)(sp);
	sw	$1, (4*1)(sp);
	sw	$2, (4*2)(sp);
	sw	$3, (4*3)(sp);
	sw	$4, (4*4)(sp);
	sw	$5, (4*5)(sp);
	sw	$6, (4*6)(sp);
	sw	$7, (4*7)(sp);
	sw	$8, (4*8)(sp);
	sw	$9, (4*9)(sp);
	sw	$10, (4*10)(sp);
	sw	$11, (4*11)(sp);
	sw	$12, (4*12)(sp);
	sw	$13, (4*13)(sp);
	sw	$14, (4*14)(sp);
	sw	$15, (4*15)(sp);
	sw	$16, (4*16)(sp);
	sw	$17, (4*17)(sp);
	sw	$18, (4*18)(sp);
	sw	$19, (4*19)(sp);
	sw	$20, (4*20)(sp);
	sw	$21, (4*21)(sp);
	sw	$22, (4*22)(sp);
	sw	$23, (4*23)(sp);
	sw	$24, (4*24)(sp);
	sw	$25, (4*25)(sp);
	sw	$26, (4*26)(sp);
	sw	$27, (4*27)(sp);
	sw	$28, (4*28)(sp);
	sw	$29, (4*29)(sp);
	sw	$30, (4*30)(sp);
	sw	$31, (4*31)(sp);
	move	a0, sp
	la	k0, c_except_handler
	jr	k0
	nop
	.set reorder