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nand read.jffs2 0x30007FC0 kernel;
从NAND读出内核：从哪读，从kernel分区
放到哪去 -0x30007FC0
nand read.jffs2 0x30007FC0 0x00200000 0x00060000
device nand0 <nandflash0>, # parts = 4
#: name size offset mask_flags 0: bootloader 0x00040000 0x00000000 0
1: params 0x00020000 0x00040000 0
2: kernel 0x00200000 0x00060000 0
3: root 0x0fda0000 0x00260000 0
active partition: nand0,0 - (bootloader) 0x00040000 @ 0x00000000
defaults: mtdids : nand0=nandflash0
mtdparts: mtdparts=nandflash0:256k@0(bootloader),128k(params),2m(kernel),-(root)
.jffs2 方便不用块对齐
bootm 0x30007FC0
flash内的内核，uimage 头部（64k） + 内核 0x30007FC0 是为了使内核的加载地址刚好为0x30008000 节省时间不必再把内核移动到加载地址
（1）根据头部移动内核到加载地址
（2）启动内核do_bootm_linux
1、u_boot告诉内核一些参数，设置启动阐述
2、跳到入口地址启动内核
setup_start_tag (bd);
setup_memory_tags (bd_t *bd)
setup_commandline_tag (bd_t *bd, char *commandline)
setup_end_tag (bd_t *bd)
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 tag_header {
u32 size;
u32 tag;
};
static void setup_start_tag (bd_t *bd)
{ params = (struct tag *) bd->bi_boot_params; · //开始开始存放地址
params->hdr.tag = ATAG_CORE; //0x54410001
params->hdr.size = tag_size (tag_core); //tag + size + core >>2 单位为4个字节
params->u.core.flags = 0;
params->u.core.pagesize = 0;
params->u.core.rootdev = 0;
params = tag_next (params); //指向下一个tag
}
static void setup_memory_tags (bd_t *bd)
{
int i;
for (i = 0; i < CONFIG_NR_DRAM_BANKS; i++)
{ //CONFIG_NR_DRAM_BANKS 1
params->hdr.tag = ATAG_MEM; //0x54410002
params->hdr.size = tag_size (tag_mem32); //
params->u.mem.start = bd->bi_dram[i].start; //0x30000000
params->u.mem.size = bd->bi_dram[i].size; //大小为初始化自定值 0x04000000
params = tag_next (params);
}
}
static void setup_commandline_tag (bd_t *bd, char *commandline)
{
char *p; //char *commandline = getenv ("bootargs");
if (!commandline) //bootargs=noinitrd root=/dev/mtdblock3 init=/linuxrc console=ttySAC0使用串口0
return;
/* eat leading white space */
for (p = commandline; *p == ‘ ‘; p++);
/* skip non-existent command lines so the kernel will still
* use its default command line. */
if (*p == ‘\0‘) return;
params->hdr.tag = ATAG_CMDLINE; //0x54410009
params->hdr.size = (sizeof (struct tag_header) + strlen (p) + 1 + 4) >> 2;
strcpy (params->u.cmdline.cmdline, p);
params = tag_next (params); }
static void setup_end_tag (bd_t *bd)
{
params->hdr.tag = ATAG_NONE;
params->hdr.size = 0;
}
u_boot: 启动内核
1、从flash里读
2、启动
a、设置启动参数
b、跳跳到入口地址
theKernel (0, bd->bi_arch_number, bd->bi_boot_params);
bd->bi_boot_params 参数地址
bd->bi_arch_number 机器id
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原文地址：http://www.cnblogs.com/CZM-/p/5076092.html
