gd_t , bd_t 结构分析

在分析板级初始化函数board_init_f 和 board_init_r 之前，先来看一下在uboot中颇为重要的 gd_t, bd_t 结构

bd_t 所对应的定义bd_info 在 arch/arm/include/asm/u-boot.h 下，主要用来保存板子参数

 typedef struct bd_info {
     int            bi_baudrate;    /* serial console baudrate 波特率串口控制台*/
     unsigned long    bi_ip_addr;    /* IP Address */
     ulong            bi_arch_number;    /* unique id for this board 板子唯一的ID */
     ulong            bi_boot_params;    /* where this board expects params  启动参数*/
     struct                /* RAM configuration  ARM的开始位置和大小*/
     {
     ulong start;
     ulong size;
     }            bi_dram[CONFIG_NR_DRAM_BANKS];
 } bd_t;

bd_info

• ulong bi_arch_number; /* unique id for this board 开发板ID*/

　　　　该变量标识每一种开发板相关的ID，该值将传递给内核，如果这个参数与内核配置的不相同，那么内核启动解压缩完成后将出现“Error:a”错误，开发板ID可以在内核arch/arm/tools/mach-types中查看

• ulong bi_boot_params; /* where this board expects params u-boot*/

　　　　传递给内核的参数的保存地址

gd_t 对应的global_data 在 arch/arm/include/asm/global_data.h，其成员主要是一些全局的系统初始化参数。当使用gd_t时需用宏定义进行声明：DECLARE_GLOBAL_DATA_PTR，指定占用寄存器R8。

  * Keep it *SMALL* and remember to set GENERATED_GBL_DATA_SIZE > sizeof(gd_t)
  */

 typedef    struct    global_data {
     bd_t        *bd;                //与板子相关的结构
     unsigned long    flags;      //指示标志，如设备已经初始化标志等
     unsigned long    baudrate;  //串口波特率
     unsigned long    have_console;    /* serial_init() was called 串口初始化标志*/
     unsigned long    env_addr;    /* Address  of Environment struct  环境变量参数地址*/
     unsigned long    env_valid;    /* Checksum of Environment valid?  检验环境变量参数是否有效 */
     unsigned long    fb_base;    /* base address of frame buffer
  frame buffer 基址*/
 #ifdef CONFIG_VFD
     unsigned char    vfd_type;    /* display type 显示类型的logo 的VFD*/
 #endif
 #ifdef CONFIG_FSL_ESDHC    //宏未在板子相关头文件中定义
     unsigned long    sdhc_clk;
 #endif
 #ifdef CONFIG_AT91FAMILY    //宏未在板子相关头文件中定义
     /* "static data" needed by at91's clock.c */
     unsigned long    cpu_clk_rate_hz;
     unsigned long    main_clk_rate_hz;
     unsigned long    mck_rate_hz;
     unsigned long    plla_rate_hz;
     unsigned long    pllb_rate_hz;
     unsigned long    at91_pllb_usb_init;
 #endif
 #ifdef CONFIG_ARM    // 宏未定义
     /* "static data" needed by most of timer.c on ARM platforms */
     unsigned long    timer_rate_hz;
     unsigned long    tbl;
     unsigned long    tbu;
     unsigned long long    timer_reset_value;
     unsigned long    lastinc;
 #endif
     unsigned long    relocaddr;    /* Start address of U-Boot in RAM   u-boot搬移到内存后的起始地址*/
     phys_size_t    ram_size;    /* RAM size */
     unsigned long    mon_len;    /* monitor len */
     unsigned long    irq_sp;        /* irq stack pointer */
     unsigned long    start_addr_sp;    /* start_addr_stackpointer */
     unsigned long    reloc_off;
 #if !(defined(CONFIG_SYS_NO_ICACHE) && defined(CONFIG_SYS_NO_DCACHE))    //宏未定义
     unsigned long    tlb_addr;
 #endif
     void        **jt;        /* jump table */
     char        env_buf[];    /* buffer for getenv() before reloc.   reloc之前getenv（）的缓冲区*/
 } gd_t;

 #define DECLARE_GLOBAL_DATA_PTR     register volatile gd_t *gd asm ("r8")

global_data