TQ2440裸板学习笔记9--引导内核

一、引导zImage

二、代码

 稍微整理一下代码，将头文件都放在include目录下。每一个模块一个头文件，这样结构比较清晰。

root@ubuntu:~/myboot_loader# tree

.

├── boot_zImage.c

├── include

│   ├── nand.h

│   ├── string.h

│   ├── uart.h

│   └── vsprintf.h

├── main.c

├── Makefile

├── nand.c

├── sdram.c

├── start.S

├── uart.c

├── u-boot.lds

└── vsprintf.c

1 directory, 13 files

2.1 main.c

#include "uart.h"
#include "nand.h"

extern int boot_zImage(unsigned long from, unsigned long size);
void main(void)
{
    uart_init();        //初始化串口
    nand_init();
    uart_printf("now boot the kernel\n");

    boot_zImage(0x200000, 0x200000);
}

程序跳到内存中的main函数之后，初始化串口和nand flash，然后引导内核。

2.2 boot_zImage.c 取自tq2440的u-boot

#include "uart.h"
#include "nand.h"
#include "string.h"

#define LINUX_KERNEL_OFFSET         0x8000
#define LINUX_PARAM_OFFSET          0x100
#define LINUX_PAGE_SIZE             0x00001000
#define LINUX_PAGE_SHIFT            12
#define LINUX_ZIMAGE_MAGIC          0x016f2818
#define DRAM_SIZE                   0x04000000
#define CONFIG_BOOTARGS             "noinitrd root=/dev/mtdblock2 init=/linuxrc console=ttySAC0 mem=128M"
#define COMMAND_LINE_SIZE           256
#define MACH_TYPE_S3C2440           168
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];
};

/*
 * Disable IRQs
 */
#define local_irq_disable()                    \
    ({                            \
        unsigned long temp;                \
    __asm__ __volatile__(                    \
    "mrs    %0, cpsr        @ local_irq_disable\n"    \
"    orr    %0, %0, #128\n"                    \
"    msr    cpsr_c, %0"                    \
    : "=r" (temp)                        \
    :                            \
    : "memory", "cc");                    \
    })

static inline void cpu_arm920_cache_clean_invalidate_all(void)
{
__asm__(
    "    mov    r1, #0\n"
    "    mov    r1, #7 << 5\n"         /* 8 segments */
    "1:    orr    r3, r1, #63 << 26\n"     /* 64 entries */
    "2:    mcr    p15, 0, r3, c7, c14, 2\n" /* clean & invalidate D index */
    "    subs    r3, r3, #1 << 26\n"
    "    bcs    2b\n"             /* entries 64 to 0 */
    "    subs    r1, r1, #1 << 5\n"
    "    bcs    1b\n"             /* segments 7 to 0 */
    "    mcr    p15, 0, r1, c7, c5, 0\n" /* invalidate I cache */
    "    mcr    p15, 0, r1, c7, c10, 4\n" /* drain WB */
    );
}

void cache_clean_invalidate(void)
{
    cpu_arm920_cache_clean_invalidate_all();
}

static inline void cpu_arm920_tlb_invalidate_all(void)
{
    __asm__(
        "mov    r0, #0\n"
        "mcr    p15, 0, r0, c7, c10, 4\n"    /* drain WB */
        "mcr    p15, 0, r0, c8, c7, 0\n"    /* invalidate I & D TLBs */
        );
}

void tlb_invalidate(void)
{
    cpu_arm920_tlb_invalidate_all();
}


void  call_linux(long a0, long a1, long a2)
{
     local_irq_disable();
    cache_clean_invalidate();
    tlb_invalidate();

__asm__(
    "mov    r0, %0\n"
    "mov    r1, %1\n"
    "mov    r2, %2\n"
    "mov    ip, #0\n"
    "mcr    p15, 0, ip, c13, c0, 0\n"    /* zero PID */
    "mcr    p15, 0, ip, c7, c7, 0\n"    /* invalidate I,D caches */
    "mcr    p15, 0, ip, c7, c10, 4\n"    /* drain write buffer */
    "mcr    p15, 0, ip, c8, c7, 0\n"    /* invalidate I,D TLBs */
    "mrc    p15, 0, ip, c1, c0, 0\n"    /* get control register */
    "bic    ip, ip, #0x0001\n"        /* disable MMU */
    "mcr    p15, 0, ip, c1, c0, 0\n"    /* write control register */
    "mov    pc, r2\n"
    "nop\n"
    "nop\n"
    : /* no outpus */
    : "r" (a0), "r" (a1), "r" (a2)
    : "r0","r1","r2","ip"
    );
}

/*
 * pram_base: base address of linux paramter
 */
static void setup_linux_param(unsigned long param_base)
{
    struct param_struct *params = (struct param_struct *)param_base;
    char *linux_cmd = CONFIG_BOOTARGS    ;

    memset((unsigned char*)params, 0, sizeof(struct param_struct));

    params->u1.s.page_size = LINUX_PAGE_SIZE;
    params->u1.s.nr_pages = (DRAM_SIZE >> LINUX_PAGE_SHIFT);

    /* set linux command line */
    memcpy(params->commandline, linux_cmd, strlen(linux_cmd) + 1);
}

int boot_zImage(unsigned long from, unsigned long size)
{
    int ret;
    unsigned long boot_mem_base;    /* base address of bootable memory */
    unsigned long to;
    unsigned long mach_type;

    boot_mem_base = 0x30000000;

    /* copy kerne image */
    to = boot_mem_base + LINUX_KERNEL_OFFSET;
    uart_printf("Copy kernel from 0x%08lx to 0x%08lx, size = 0x%08lx ...\n ", from, to, size);

    nand_read_page((unsigned char *)to, (unsigned long)from, (int)size);

    uart_printf("read over! next check \n");

    //uart_printf("read ok!\n");

    if (*(unsigned long *)(to + 9*4) != LINUX_ZIMAGE_MAGIC) {
        uart_printf("Warning: this binary is not compressed linux kernel image\n");
        uart_printf("zImage magic = 0x%08lx\n", *(unsigned long *)(to + 9*4));
        return -1;
    }

    /* Setup linux parameters and linux command line */
    setup_linux_param(boot_mem_base + LINUX_PARAM_OFFSET);

    /* Get machine type */
    mach_type = MACH_TYPE_S3C2440;
    //    printk("MACH_TYPE = %d\n", mach_type);

    /* Go Go Go */
    uart_printf("NOW, Booting Linux......\n");
    call_linux(0, mach_type, to);

    return 0;
}

boot_zImage函数，

   a. 首先将内核从nand flash的0x00200000复制到0x30008000，复制大小为0x00200000

   b. 检查文件头是否正确

   c. 在u-boot与内核约定的参数起始地址0x30000100处，设置linux的启动参数

   d. 最后启动内核 

不过这个程序还存在问题：启动时会卡在nand_read_page处大约20秒左右，下一步看问题出在什么地方？

三、

   3.1 这样一个最最最最基本的bootloader就完成了，

  root@ubuntu:~/myboot_loader# ll  u-boot.bin 

  -rwxr-xr-x 1 root root 6796 2012-05-31 00:44 u-boot.bin*

   大小是6796，大约是6.7K.

   3.2 这个bootloader可以进一步精简，把vsprintf去掉之后

root@ubuntu:~/myboot_loader_noprint# ll u-boot.bin 

-rwxr-xr-x 1 root root 2868 2012-05-31 00:48 u-boot.bin*

   大小只有2868个字节。当然如果是小于4K，程序就可以直接在sram中进行，那么先把bootloader复制到内存这一步也可以省略，相信代码可以更小。

 myboot_loader.rar  (将后缀名改为tar.gz, 卡在nand_read_page中大约20秒)

  myboot_loader_noprint.rar   (将后缀名改为tar.gz，卡在nand_read_page中大约20秒，并且有时会直接卡死)