mini2440之动手写简易bootloader
Bootloader 它的终极使命就是启动内核，它的主要工作：在上电之后在硬件上进行一系列的初始化，为Linux内核启动铺路。具体的就是设置看门狗、设置系统时钟、初始化SDRAM与NANDflash控制器、代码重定位等，最后将内核从nandflash上拷贝到内存中，传递参数，跳转执行。
一、创建start.S文件
.text .global _start _start: /* close the watchdog */ ldr r0, =0x53000000 mov r1, #0 str r1, [r0] /* close the watchdog */ @关闭看门狗 @数据手册：WTCON 0x53000000 R/W Watchdog timer control register /* set the clock */ ldr r0, =0x4c000014 mov r1, #0x03; @ FCLK:HCLK:PCLK=1:2:4, HDIVN=1,PDIVN=1 str r1, [r0] mrc p15, 0, r1, c1, c0, 0 /* read */ orr r1, r1, #0xc0000000 /* set asynchronous bus mode */ mcr p15, 0, r1, c1, c0, 0 /* write */ ldr r0, =0x4c000004 ldr r1, =((0x5c<<12)|(0x01<<4)|(0x02)) @MPLL:200MHz str r1, [r0] /* set the clock */ @设置系统时钟 @如果HDIVN不是0，CPU的总线模式应该设置成asynchronous bus mode /* enable the ICACHE */ mrc p15, 0, r0, c1, c0, 0 @ read control register orr r0, r0, #(1<<12) mcr p15, 0, r0, c1, c0, 0 @ write back /* enable the ICACHE */ @使能高速缓存，为系统提速，此段可不要，但程序执行速度要慢 /* init the SDRAM */ ldr r0, =0x48000000 @MEM_CTL_BASE adr r1, config /* sdram config address */ add r3, r0, #(52) @13*4 1: ldr r2, [r1], #4 str r2, [r0], #4 cmp r0, r3 bne 1b /* init the SDRAM */ @初始化SDRAM @根据数据手册对与SDRAM有关的13个寄存器进行配置 /* relocate */ ldr sp, =0x34000000 bl nand_init mov r0, #0 ldr r1, =_start ldr r2, =__bss_start sub r2, r2, r1 bl copy_code_to_sdram bl clear_bss /* relocate */ @把bootloader本身的代码从nandflash复制到它的链接地址去 /* go to main */ ldr lr, =halt ldr pc, =main halt: b halt /* go to main */ @跳转到main函数执行 config: .long 0x22011110 @BWSCON .long 0x00000700 @BANKCON0 .long 0x00000700 @BANKCON1 .long 0x00000700 @BANKCON2 .long 0x00000700 @BANKCON3 .long 0x00000700 @BANKCON4 .long 0x00000700 @BANKCON5 .long 0x00018005 @BANKCON6 .long 0x00018005 @BANKCON7 .long 0x008C04F4 @REFRESH .long 0x000000B1 @BANKSIZE .long 0x00000030 @MRSRB6 .long 0x00000030 @MRSRB7
/* nandflash controller */
#define NFCONF (*((volatile unsigned long *)0x4E000000))
#define NFCONT (*((volatile unsigned long *)0x4E000004))
#define NFCMMD (*((volatile unsigned char *)0x4E000008))
#define NFADDR (*((volatile unsigned char *)0x4E00000C))
#define NFDATA (*((volatile unsigned char *)0x4E000010))
#define NFSTAT (*((volatile unsigned char *)0x4E000020))
/* GPIO */
#define GPHCON (*(volatile unsigned long *)0x56000070)
#define GPHUP (*(volatile unsigned long *)0x56000078)
/* UART registers*/
#define ULCON0 (*(volatile unsigned long *)0x50000000)
#define UCON0 (*(volatile unsigned long *)0x50000004)
#define UFCON0 (*(volatile unsigned long *)0x50000008)
#define UMCON0 (*(volatile unsigned long *)0x5000000c)
#define UTRSTAT0 (*(volatile unsigned long *)0x50000010)
#define UTXH0 (*(volatile unsigned char *)0x50000020)
#define URXH0 (*(volatile unsigned char *)0x50000024)
#define UBRDIV0 (*(volatile unsigned long *)0x50000028)
#define TXD0READY (1<<2)
void nand_read(unsigned int addr, unsigned char *buf, unsigned int len);
void copy_code_to_sdram(unsigned char *src, unsigned char *dest, unsigned int len)
{
nand_read((unsigned int)src, dest, len);
}
void clear_bss(void)
{
extern int __bss_start, __bss_end;
int *p = &__bss_start;
for (; p < &__bss_end; p++) *p = 0;
}
void nand_init(void)
{
#define TACLS 0
#define TWRPH0 1
#define TWRPH1 0
/* sequence */
NFCONF = (TACLS<<12)|(TWRPH0<<8)|(TWRPH1<<4);
/* enable controller,init ECC,disable CS */
NFCONT = (1<<4)|(1<<1)|(1<<0);
}
void nand_select(void)
{
NFCONT &= ~(1<<1);
}
void nand_deselect(void)
{
NFCONT |= (1<<1);
}
void nand_cmd(unsigned char cmd)
{
volatile int i;
NFCMMD = cmd;
for (i = 0; i < 10; i++);
}
void nand_addr(unsigned int addr)
{
unsigned int col = addr % 2048;
unsigned int page = addr / 2048;
volatile int i;
NFADDR = col & 0xff;
for (i = 0; i < 10; i++);
NFADDR = (col >> 8) & 0xff;
for (i = 0; i < 10; i++);
NFADDR = page & 0xff;
for (i = 0; i < 10; i++);
NFADDR = (page >> 8) & 0xff;
for (i = 0; i < 10; i++);
NFADDR = (page >> 16) & 0xff;
for (i = 0; i < 10; i++);
}
void nand_wait_ready(void)
{
while (!(NFSTAT & 1));
}
unsigned char nand_data(void)
{
return NFDATA;
}
void nand_read(unsigned int addr, unsigned char *buf, unsigned int len)
{
int col = addr % 2048;
int i = 0;
/* select */
nand_select();
while (i < len)
{
/* read cmd 00h */
nand_cmd(0x00);
/* send addr */
nand_addr(addr);
/* read cmd 30h */
nand_cmd(0x30);
/* check */
nand_wait_ready();
/* read data */
for (; (col < 2048) && (i < len); col++)
{
buf[i] = nand_data();
i++;
addr++;
}
col = 0;
}
/* deselect */
nand_deselect();
}
#define PCLK 50000000 // PCLK:50MHz
#define UART_CLK PCLK // UART0:PCLK
#define UART_BAUD_RATE 115200 // baudrate
#define UART_BRD ((UART_CLK / (UART_BAUD_RATE * 16))-1)
/*115200,8N1,none*/
void uart0_init(void)
{
GPHCON |= 0xa0; // GPH2,GPH3:TXD0,RXD0
GPHUP = 0x0c; // GPH2,GPH3 pull up
ULCON0 = 0x03;
UCON0 = 0x05;
UFCON0 = 0x00;
UMCON0 = 0x00;
UBRDIV0 = UART_BRD; // 115200
}
void putc(unsigned char c)
{
while (!(UTRSTAT0 & TXD0READY));
UTXH0 = c;
}
void puts(char *str)
{
int i = 0;
while (str[i])
{
putc(str[i]);
i++;
}
}
完成了 nandflash与串口的初始化。
三、创建boot.c文件
#include "setup.h"
extern void uart0_init(void);
extern void nand_read(unsigned int addr, unsigned char *buf, unsigned int len);
extern void puts(char *str);
extern void puthex(unsigned int val);
static struct tag *params;
void setup_start_tag(void)
{
params = (struct tag *)0x30000100;
params->hdr.tag = ATAG_CORE;
params->hdr.size = tag_size (tag_core);
params->u.core.flags = 0;
params->u.core.pagesize = 0;
params->u.core.rootdev = 0;
params = tag_next (params);
}
void setup_memory_tags(void)
{
params->hdr.tag = ATAG_MEM;
params->hdr.size = tag_size (tag_mem32);
params->u.mem.start = 0x30000000;
params->u.mem.size = 64*1024*1024;
params = tag_next (params);
}
int strlen(char *str)
{
int i = 0;
while (str[i])
{
i++;
}
return i;
}
void strcpy(char *dest, char *src)
{
while ((*dest++ = *src++) != '\0');
}
void setup_commandline_tag(char *cmdline)
{
int len = strlen(cmdline) + 1;
params->hdr.tag = ATAG_CMDLINE;
params->hdr.size = (sizeof (struct tag_header) + len + 3) >> 2;
strcpy (params->u.cmdline.cmdline, cmdline);
params = tag_next (params);
}
void setup_end_tag(void)
{
params->hdr.tag = ATAG_NONE;
params->hdr.size = 0;
}
int main(void)
{
void (*theKernel)(int zero, int arch, unsigned int params);
uart0_init();
/* copy kernel to memory from nandflash */
puts("MINI2440 simple bootloader\n\r");
puts("\n\r");
puts("start ...\n\r");
puts("\n\r");
puts("copy kernel to memory from nandflash ...\n\r");
nand_read(0x60000, (unsigned char *)0x30008000, 0x500000);
@起始地址0x60000，长度0x500000，内存地址30008000
puts("\n\r");
puts("\n\r");
/* set params */
puts("Setting params ...\n\r");
setup_start_tag();
setup_memory_tags();
setup_commandline_tag("noinitrd root=/dev/mtdblock3 init=/linuxrc console=ttySAC0");
setup_end_tag();
puts("\n\r");
/* boot */
puts("Boot ...\n\r");
theKernel = (void (*)(int, int, unsigned int))0x30008000;
theKernel(0, 1999, 0x30000100);
@注意，mini2440机器码1999
/*
* mov r0, #0
* ldr r1, =1999
* ldr r2, =0x30000100
* mov pc, #0x30008000
*/
puts("Error!\n\r");
/* error */
return -1;
}
四、拷贝setup.h文件
/*
* linux/include/asm/setup.h
*
* Copyright (C) 1997-1999 Russell King
*
* 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.
*
* Structure passed to kernel to tell it about the
* hardware it's running on. See linux/Documentation/arm/Setup
* for more info.
*
* NOTE:
* This file contains two ways to pass information from the boot
* loader to the kernel. The old struct param_struct is deprecated,
* but it will be kept in the kernel for 5 years from now
* (2001). This will allow boot loaders to convert to the new struct
* tag way.
*/
#ifndef __ASMARM_SETUP_H
#define __ASMARM_SETUP_H
#define u8 unsigned char
#define u16 unsigned short
#define u32 unsigned long
/*
* Usage:
* - do not go blindly adding fields, add them at the end
* - when adding fields, don't rely on the address until
* a patch from me has been released
* - unused fields should be zero (for future expansion)
* - this structure is relatively short-lived - only
* guaranteed to contain useful data in setup_arch()
*/
#define COMMAND_LINE_SIZE 1024
/* This is the old deprecated way to pass parameters to the kernel */
struct param_struct {
union {
struct {
unsigned long page_size; /* 0 */
unsigned long nr_pages; /* 4 */
unsigned long ramdisk_size; /* 8 */
unsigned long flags; /* 12 */
#define FLAG_READONLY 1
#define FLAG_RDLOAD 4
#define FLAG_RDPROMPT 8
unsigned long rootdev; /* 16 */
unsigned long video_num_cols; /* 20 */
unsigned long video_num_rows; /* 24 */
unsigned long video_x; /* 28 */
unsigned long video_y; /* 32 */
unsigned long memc_control_reg; /* 36 */
unsigned char sounddefault; /* 40 */
unsigned char adfsdrives; /* 41 */
unsigned char bytes_per_char_h; /* 42 */
unsigned char bytes_per_char_v; /* 43 */
unsigned long pages_in_bank[4]; /* 44 */
unsigned long pages_in_vram; /* 60 */
unsigned long initrd_start; /* 64 */
unsigned long initrd_size; /* 68 */
unsigned long rd_start; /* 72 */
unsigned long system_rev; /* 76 */
unsigned long system_serial_low; /* 80 */
unsigned long system_serial_high; /* 84 */
unsigned long mem_fclk_21285; /* 88 */
} s;
char unused[256];
} u1;
union {
char paths[8][128];
struct {
unsigned long magic;
char n[1024 - sizeof(unsigned long)];
} s;
} u2;
char commandline[COMMAND_LINE_SIZE];
};
/*
* The new way of passing information: a list of tagged entries
*/
/* The list ends with an ATAG_NONE node. */
#define ATAG_NONE 0x00000000
struct tag_header {
u32 size;
u32 tag;
};
/* The list must start with an ATAG_CORE node */
#define ATAG_CORE 0x54410001
struct tag_core {
u32 flags; /* bit 0 = read-only */
u32 pagesize;
u32 rootdev;
};
/* it is allowed to have multiple ATAG_MEM nodes */
#define ATAG_MEM 0x54410002
struct tag_mem32 {
u32 size;
u32 start; /* physical start address */
};
/* VGA text type displays */
#define ATAG_VIDEOTEXT 0x54410003
struct tag_videotext {
u8 x;
u8 y;
u16 video_page;
u8 video_mode;
u8 video_cols;
u16 video_ega_bx;
u8 video_lines;
u8 video_isvga;
u16 video_points;
};
/* describes how the ramdisk will be used in kernel */
#define ATAG_RAMDISK 0x54410004
struct tag_ramdisk {
u32 flags; /* bit 0 = load, bit 1 = prompt */
u32 size; /* decompressed ramdisk size in _kilo_ bytes */
u32 start; /* starting block of floppy-based RAM disk image */
};
/* describes where the compressed ramdisk image lives (virtual address) */
/*
* this one accidentally used virtual addresses - as such,
* its depreciated.
*/
#define ATAG_INITRD 0x54410005
/* describes where the compressed ramdisk image lives (physical address) */
#define ATAG_INITRD2 0x54420005
struct tag_initrd {
u32 start; /* physical start address */
u32 size; /* size of compressed ramdisk image in bytes */
};
/* board serial number. "64 bits should be enough for everybody" */
#define ATAG_SERIAL 0x54410006
struct tag_serialnr {
u32 low;
u32 high;
};
/* board revision */
#define ATAG_REVISION 0x54410007
struct tag_revision {
u32 rev;
};
/* initial values for vesafb-type framebuffers. see struct screen_info
* in include/linux/tty.h
*/
#define ATAG_VIDEOLFB 0x54410008
struct tag_videolfb {
u16 lfb_width;
u16 lfb_height;
u16 lfb_depth;
u16 lfb_linelength;
u32 lfb_base;
u32 lfb_size;
u8 red_size;
u8 red_pos;
u8 green_size;
u8 green_pos;
u8 blue_size;
u8 blue_pos;
u8 rsvd_size;
u8 rsvd_pos;
};
/* command line: \0 terminated string */
#define ATAG_CMDLINE 0x54410009
struct tag_cmdline {
char cmdline[1]; /* this is the minimum size */
};
/* acorn RiscPC specific information */
#define ATAG_ACORN 0x41000101
struct tag_acorn {
u32 memc_control_reg;
u32 vram_pages;
u8 sounddefault;
u8 adfsdrives;
};
/* footbridge memory clock, see arch/arm/mach-footbridge/arch.c */
#define ATAG_MEMCLK 0x41000402
struct tag_memclk {
u32 fmemclk;
};
struct tag {
struct tag_header hdr;
union {
struct tag_core core;
struct tag_mem32 mem;
struct tag_videotext videotext;
struct tag_ramdisk ramdisk;
struct tag_initrd initrd;
struct tag_serialnr serialnr;
struct tag_revision revision;
struct tag_videolfb videolfb;
struct tag_cmdline cmdline;
/*
* Acorn specific
*/
struct tag_acorn acorn;
/*
* DC21285 specific
*/
struct tag_memclk memclk;
} u;
};
struct tagtable {
u32 tag;
int (*parse)(const struct tag *);
};
#define tag_member_present(tag,member) \
((unsigned long)(&((struct tag *)0L)->member + 1) \
<= (tag)->hdr.size * 4)
#define tag_next(t) ((struct tag *)((u32 *)(t) + (t)->hdr.size))
#define tag_size(type) ((sizeof(struct tag_header) + sizeof(struct type)) >> 2)
#define for_each_tag(t,base) \
for (t = base; t->hdr.size; t = tag_next(t))
/*
* Memory map description
*/
#define NR_BANKS 8
struct meminfo {
int nr_banks;
unsigned long end;
struct {
unsigned long start;
unsigned long size;
int node;
} bank[NR_BANKS];
};
extern struct meminfo meminfo;
#endif
五、创建boot.lds文件
SECTIONS {
. = 0x33f80000;
.text : { *(.text) }
. = ALIGN(4);
.rodata : {*(.rodata*)}
. = ALIGN(4);
.data : { *(.data) }
. = ALIGN(4);
__bss_start = .;
.bss : { *(.bss) *(COMMON) }
__bss_end = .;
}
六、Makefile
CC = arm-linux-gcc
LD = arm-linux-ld
AR = arm-linux-ar
OBJCOPY = arm-linux-objcopy
OBJDUMP = arm-linux-objdump
CFLAGS := -Wall -O2
CPPFLAGS := -nostdinc -nostdlib -fno-builtin
objs := start.o init.o boot.o
boot.bin: $(objs)
${LD} -Tboot.lds -o boot.elf $^
${OBJCOPY} -O binary -S boot.elf $@
${OBJDUMP} -D -m arm boot.elf > boot.dis
%.o:%.c
${CC} $(CPPFLAGS) $(CFLAGS) -c -o $@ $<
%.o:%.S
${CC} $(CPPFLAGS) $(CFLAGS) -c -o $@ $<
clean:
rm -f *.o *.bin *.elf *.dis