cpu.c

这是Linux环境下的内核引导程序miniboot0.8

#include "cpu.h"
#include "types.h"
#include "mmu.h"
/*
 *	读控制寄存器
 */
u32 read_control_register()
{
	u32 reg;
	
	asm volatile(
		"mrc p15,0,r0,c1,c0,0 \n\t"
		"str r0,%0 \n\t"
		:
		:"m"(reg)
		:"r0"
	);
	
	reg&=~(0x7FFF)<<15;
	reg&=~(0x3)<<10;
	reg|=0xf<<3;

	return reg;
}
/*
 *	写控制寄存器
 */
void write_control_register(u32 value)
{
	asm volatile(
		"ldr r0,%0 \n\t"
		"mcr p15,0,r0,c1,c0,0 \n\t"
		:
		:"m"(value)
		:"r0"
	);
}

void set_ctrl_bit(u32* reg_data,u8 offset,u8 bit)
{
	*reg_data&=~(0x1)<<offset;
	*reg_data|=bit<<offset;
}

void load_page_directory(u32 page_directory_addr)
{
	asm volatile(
		"ldr r0,%0\n\t"
		"mcr p15,0,r0,c2,c0,0\n\t"
		:
		:"m"(page_directory_addr)
		:"r0"
	);
}

/*
 *	使ICache和DCache无效
 */
void invalidate_IDCache()
{
	asm volatile(
		"ldr r0,=0x00000000 \n\t"
		"mcr p15,0,r0,c7,c7,0 \n\t"
		:
		:
		:"r0"
	);
}
/*
 *	使I TLB和 D TLB无效
 */
void invalidate_TLBs()
{
	asm volatile(
		"ldr r0,=0x00000000 \n\t"
		"mcr p15,0,r0,c8,c7,0 \n\t"
		:
		:
		:"r0"
	);	
}

/*
 *	读domain控制寄存器
 */
u32 read_domain()
{
	u32 reg=0;
	
	asm volatile(
		"mrc p15,0,r0,c3,c0,0 \n\t"
		"str r0,%0 \n\t"
		:
		:"m"(reg)
		:"r0"
	);
	
	return reg;
}

/*
 *	写domain控制寄存器
 */
void write_domain(u32 value)
{
	asm volatile(
		"ldr r0,%0 \n\t"
		"mcr p15,0,r0,c3,c0,0 \n\t"
		:
		:"m"(value)
		:"r0"
	);
}

void setup_domain(u32 value)
{
	write_domain(value);
}


void arm920_init(void)
{
	unsigned int ctrl_reg=read_control_register();
	
	/*
	 *	Domain Access Control Register
	 *	
	 *	d15 d14 d13 d12 d11 d10 d9 d8 d7 d6 d5 d4 d3 d2 d1 d0
	 *	00  00  00  00  00  00  00 00 00 00 00 00 00 00 11 01
	 *	
	 *	domain 0: client  (01)
	 *	domain 1: mamager (11)
	 */
	setup_domain(0x0000000D);
	
	load_page_directory(DIRECTORY_BASE);

	set_ctrl_bit(&ctrl_reg,V,1);
	set_ctrl_bit(&ctrl_reg,I,1);//开启ICache
	set_ctrl_bit(&ctrl_reg,S,0);
	set_ctrl_bit(&ctrl_reg,R,0);
	set_ctrl_bit(&ctrl_reg,B,0);
	set_ctrl_bit(&ctrl_reg,C,1);//开启DCache
	set_ctrl_bit(&ctrl_reg,A,0);//Fault checking disabled
	set_ctrl_bit(&ctrl_reg,M,1);//开启MMU
	
	write_control_register(ctrl_reg);
}