bootloader功能介绍
初始化开发板上主要硬件(时钟,内存,硬盘),
把操作系统从硬盘拷贝到内存,然后让cpu跳转到内存中执行操作系统。
boot阶段
1.关闭影响CPU正常执行的外设
-关闭看门狗(watch dog) WTCON 0xE2700000
-关闭中断 CPSR I和F位设置为1,关闭,不响应任何中断。
2.初始化时钟
-倍频到1Ghz,为外设分频
*串口驱动
3.初始化内存控制器,DDRAM
-验证内存,往里面写一个值,然后再读出来
4.初始化硬盘,nand Flash
-nand flash 读驱动(从nand往外读数据)
loader阶段
1.从硬盘指定的地址加载kernel到内存指定的地址。
2.跳转到内存kernel所在的地址,执行
附加功能:
实现bootloader中shell(命令解释器)
附加功能:
实现bootloader中shell(命令解释器)
uboot中支持的命令,
help
loadb 下载程序, kermit 协议
go 0X21000000;
例如:在uboot中直接控制蜂鸣器
mm 0xe02000a0 0x1(控制寄存器)
mm 0xe02000a4 0x1(数据寄存器)
常用调试手段:
1.led点灯大法
2.串口调试,uart_getchar,uart_putchar,进一步实现stdio.h
时钟初始化设置
pll 锁相环, 倍频
串口工作原理
串口工作核心图
#define ULCON0 *((volatile unsigned int *)0XE2900000)
volatile 关键字,防止编译器做优化,每次读取寄存器的值,都是重新读取寄存器。
- //start.s
- AREA start_main,CODE, READONLY
- ENTRY
- IMPORT uart_test
- START
- B uart_test
-
- END
- //uart.c
- #define ULCON0 *((volatile unsigned int *)0XE2900000)
- #define UCON0 *((volatile unsigned int *)0XE2900004)
- #define UTRSTAT0 *((volatile unsigned int *)0XE2900010)
- #define UTXH0 *((volatile unsigned int *)0XE2900020)
- #define URXH0 *((volatile unsigned int *)0XE2900024)
- #define UBRDIV0 *((volatile unsigned int *)0XE2900028)
- #define UDIVSLOT0 *((volatile unsigned int *)0XE290002C)
- #define GPACON0 *((volatile unsigned int *)0XE0200000)
- void uart_init(void)
- {
- //串口管脚设置成功能态
- GPACON0 = 0x22;
- //设置8 N 1
- ULCON0 = 0X3;
- //设置轮询工作模式
- UCON0 = 0X5;
- //设置波特率
- UBRDIV0 = 34;
- UDIVSLOT0 = 0XDDDD;
-
- }
- char uart_getchar(void)
- {
- char ch;
- //如果有数据到达,状态寄存器第0位置1
- //判断状态位是否为1,决定读接收缓冲寄存器,读到的值作为函数的返回值
- while (!(UTRSTAT0 & 0x1))
- ;
- ch = URXH0;
- return ch;
- }
- void uart_putchar(char ch)
- {
- //如果状态寄存器第1为置1,表示发送单元为空,可以发送数据
- //把ch赋值到发送缓冲寄存器里,状态寄存器第1为置0, 自动发送,当发送完毕
- while (!(UTRSTAT0 & 0X2))
- ;
- UTXH0 = ch;
- }
- void uart_test(void)
- {
- char ch;
-
- uart_init();
- uart_putchar('a');
- uart_putchar('b');
- uart_putchar('c');
- //串口回显功能
- while (1)
- {
- ch = uart_getchar();
- uart_putchar(ch);
- }
- }
内存工作原理
--------------------------------------------------
NandFlash工作原理
内存是总线设备,nandflash属于非总线设备。
没有地址线, 只有数据线。
内存:总线数据, nandflash:非总线设备。
命令、地址、数据复用端口。
忙闲位。
裸板操作NandFlash的示例代码:
- #define NFCONF (*(volatile unsigned int *)0xB0E00000)
- #define NFCONT (*(volatile unsigned int *)0xB0E00004)
- #define NFCMMD (*(volatile unsigned int *)0xB0E00008)
- #define NFADDR (*(volatile unsigned int *)0xB0E0000C)
- #define NFDATA (*(volatile unsigned int *)0xB0E00010)
- #define NFSTAT (*(volatile unsigned int *)0xB0E00028)
-
- #define MP0_3CON (*(volatile unsigned int *)0xE0200320)
-
- #define PAGE_SIZE 2048
-
- void nand_init(void)
- {
- //[15:12]TACLS = 1->(1) 1/133Mhz = 7.5ns
- //[11:8] TWRPH0 = 1->(1+7) 7.5ns*2 = 15ns
- //[7:4] TWRPH1 = 1->(1+1) 7.5ms *2 = 15ns
- NFCONF |= 1<<2 | 1<< 8 | 1<< 4;
- //AdrCycle [1]1=5 address cycle
- NFCONF |= 1<<1;
- //MODE [0] NAND Flash controller operating node
- // 0=disable nand flash controller
- // *1 = enable nand flash controller
- NFCONT |= 1<<0;
- //Reg_nCE0 [1] nandflash memort nRCS[0] signal control
- // *0 = force nRCS[0] to low (enable chip select)
- // 1 = force nRCS[0] to high(disable chip select)
- NFCONT &= ~(1<<1);
- //GPIO functional mux setting
- // 0010 = NF_xxx
- MP0_3CON = 0X22222222;
- return ;
- }
-
- void nand_read_id(char id[])
- {
- int i;
- //write read_id cmd 90th
- NFCMMD = 0X90;
- //write address 00h
- NFADDR = 0x00;
- for(i=0; i<5; i++)
- {
- id[i] = NFDATA;
- }
- return ;
- }
-
- void nand_read_page(int addr, char buf[])
- {
- int i;
- char tmp;
- //write read_page cmd 00h
- NFCMMD = 0X00;
- //write 5 address
- NFADDR = (addr >> 0) & 0xFF;
- NFADDR = (addr >> 8) & 0x7;
- NFADDR = (addr >> 11) & 0xFF;
- NFADDR = (addr >> 19) & 0xFF;
- NFADDR = (addr >> 27) & 0x1;
- //write read_page cmd 30h
- NFCMMD = 0X30;
- //wait for R/nB -->ready
- while( (NFSTAT &(1<<0))==0 )
- ;
- //read data 2048 bytes
- for(i=0; i<PAGE_SIZE; i++)
- {
- buf[i] = NFDATA;
- }
- for (i=0; i<64; i++)
- {
- tmp = NFDATA;
- }
- return ;
-
- }
-
- void nand_read(int nand_addr, char *sdram_addr, int size)
- {
- int pages = (size -1)/PAGE_SIZE + 1;
- int i;
-
- for (i=0; i<pages; i++)
- {
- nand_read_page(nand_addr + i*PAGE_SIZE, sdram_addr + i*PAGE_SIZE);
- }
-
- }
uboot中操作NandFlash的示例代码:
//s3c2440_nand.c
- #include <common.h>
-
- #if 0
- #define DEBUGN printf
- #else
- #define DEBUGN(x,args ...){}
- #endif
- #include <nand.h>
- #include <asm/arch/s3c24x0_cpu.h>
- #include <asm/arch/s3c2410.h>
- #include <asm/io.h>
-
- #define __REGb(x) (*(volatile unsigned char *)(x))
- #define __REGi(x) (*(volatile unsigned int *)(x))
-
-
- #define NF_BASE 0x4e000000
-
- #define NFCONF __REGi(NF_BASE + 0x0)
- #define NFCONT __REGi(NF_BASE + 0x4)
- #define NFCMD __REGb(NF_BASE + 0x8)
- #define NFADDR __REGb(NF_BASE + 0xc)
- #define NFDATA __REGb(NF_BASE + 0x10)
- #define NFMECCD0 __REGi(NF_BASE + 0x14)
- #define NFMECCD1 __REGi(NF_BASE + 0x18)
- #define NFSECCD __REGi(NF_BASE + 0x1C)
- #define NFSTAT __REGb(NF_BASE + 0x20)
- #define NFSTAT0 __REGi(NF_BASE + 0x24)
- #define NFSTAT1 __REGi(NF_BASE + 0x28)
- #define NFMECC0 __REGi(NF_BASE + 0x2C)
- #define NFMECC1 __REGi(NF_BASE + 0x30)
- #define NFSECC __REGi(NF_BASE + 0x34)
- #define NFSBLK __REGi(NF_BASE + 0x38)
- #define NFEBLK __REGi(NF_BASE + 0x3C)
-
- #define S3C2440_NFCONT_nCE (1<<1)
- #define S3C2440_ADDR_NALE 0x08
- #define S3C2440_ADDR_NCLE 0x0c
-
-
-
- #ifdef CONFIG_NAND_SPL
-
- /* in the early stage of NAND flash booting, printf() is not available */
- #define printf(fmt, args...)
-
- static void nand_read_buf(struct mtd_info *mtd, u_char *buf, int len)
- {
- int i;
- struct nand_chip *this = mtd->priv;
-
- for (i = 0; i < len; i++)
- buf[i] = readb(this->IO_ADDR_R);
- }
- #endif
-
- ulong IO_ADDR_W = NF_BASE;
- static void s3c2440_hwcontrol(struct mtd_info *mtd, int cmd, unsigned int ctrl)
- {
- struct nand_chip *chip = mtd->priv;
- DEBUGN("hwcontrol(): 0x%02x 0x%02x\n", cmd, ctrl);
- if (ctrl & NAND_CTRL_CHANGE) {
- IO_ADDR_W = NF_BASE;
- if (!(ctrl & NAND_CLE))
- IO_ADDR_W |= S3C2440_ADDR_NCLE;
- if (!(ctrl & NAND_ALE))
- IO_ADDR_W |= S3C2440_ADDR_NALE;
-
- if (ctrl & NAND_NCE)
- NFCONT &= ~ S3C2440_NFCONT_nCE;
- else
- NFCONT |= S3C2440_NFCONT_nCE;
- }
- if (cmd != NAND_CMD_NONE)
- writeb(cmd, (void *)IO_ADDR_W);
- }
-
-
-
- static int s3c2440_dev_ready(struct mtd_info *mtd)
- {
- DEBUGN("dev_ready\n");
- return(NFSTAT & 0x01);
- }
-
- #ifdef CONFIG_S3C2410_NAND_HWECC
- void s3c2410_nand_enable_hwecc(struct mtd_info *mtd, int mode)
- {
- struct s3c2410_nand *nand = s3c2410_get_base_nand();
- debugX(1, "s3c2410_nand_enable_hwecc(%p, %d)\n", mtd, mode);
- writel(readl(&nand->NFCONF) | S3C2410_NFCONF_INITECC, &nand->NFCONF);
- }
-
- static int s3c2410_nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat,
- u_char *ecc_code)
- {
- struct s3c2410_nand *nand = s3c2410_get_base_nand();
- ecc_code[0] = readb(&nand->NFECC);
- ecc_code[1] = readb(&nand->NFECC + 1);
- ecc_code[2] = readb(&nand->NFECC + 2);
- debugX(1, "s3c2410_nand_calculate_hwecc(%p,): 0x%02x 0x%02x 0x%02x\n",
- mtd , ecc_code[0], ecc_code[1], ecc_code[2]);
-
- return 0;
- }
-
- static int s3c2410_nand_correct_data(struct mtd_info *mtd, u_char *dat,
- u_char *read_ecc, u_char *calc_ecc)
- {
- if (read_ecc[0] == calc_ecc[0] &&
- read_ecc[1] == calc_ecc[1] &&
- read_ecc[2] == calc_ecc[2])
- return 0;
-
- printf("s3c2410_nand_correct_data: not implemented\n");
- return -1;
- }
- #endif
-
- int board_nand_init(struct nand_chip *nand)
- {
- u_int32_t cfg;
- u_int8_t tacls, twrph0, twrph1;
- struct s3c24x0_clock_power *clk_power = s3c24x0_get_base_clock_power();
-
- DEBUGN("board_nand_init()\n");
-
- writel(readl(&clk_power->CLKCON) | (1 << 4), &clk_power->CLKCON);
-
- /* initialize hardware */
- twrph0 = 4;
- twrph1 =2;
- tacls = 0;
-
- cfg = ((tacls<<12)|(twrph0<<8)|(twrph1<<4));
- NFCONF=cfg;
- cfg = ((1<<6)|(1<<4)|(0<<1)|(1<<0));
- NFCONT=cfg;
- /* initialize nand_chip data structure */
- nand->IO_ADDR_R = nand->IO_ADDR_W = (void *)0x4e000010;
-
-
- /* read_buf and write_buf are default */
- /* read_byte and write_byte are default */
-
- /* hwcontrol always must be implemented */
- nand->cmd_ctrl = s3c2440_hwcontrol;
- nand->dev_ready = s3c2440_dev_ready;
- nand->ecc.mode = NAND_ECC_SOFT;
-
- DEBUGN("end of nand_init\n");
-
- return 0;
- }
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