U-BOOT之五:gd_t和bd_t数据结构简介

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      在start_armboot()函数中,gd_tbd_tu-boot中两个重要的数据结构,在初始化操作很多都要靠这两个数据结构来保存或传递。分别定义在./include/asm-arm/global_data.h./include/asm-arm/u-boot.h

      1gd_t: global data数据结构定义,位于文件include/asm-arm/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

/*
*The following data structure is placed in some memory wich is
*available very early after boot (like DPRAM on MPC8xx/MPC82xx, or
*some locked parts of the data cache) to allow for a minimum set of
*global variables during system initialization (until we have set
*up the memory controller so that we can use RAM).
*
* Keep it*SMALL* and remember to set CFG_GBL_DATA_SIZE > sizeof(gd_t)
*CFG_GBL_DATA_SIZE
config文件中定义,start.S中会根据这个值分配栈空间给global_data
*/

ypedef struct global_data {
bd_t
*bd;                                  //struct board_info
指针,保存板子信息
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;
   //
串口初始化标志
unsigned long env_addr;          //Address of Environment struct
,环境参数地址
unsigned long env_valid;          //
环境参数CRC检验有效标志
unsigned long fb_base;             //frame buffer
的基址
#ifdefCONFIG_VFD
unsigned char vfd_type;
           /*display type */
#endif
#if 0
unsigned long cpu_clk;
            /* CPU clock in Hz! */
unsignedlong bus_clk;
unsigned long ram_size;            
/*RAM size */
unsigned long reset_status;
      /*reset status register at boot */
#endif
void **jt;
                                   /*jump table */
} gd_t;


/*
*Global Data Flags
*/

#defineGD_FLG_RELOC0x00001       /*Code was relocated to RAM */
#define GD_FLG_DEVINIT 0x00002     /*Devices have been initialized */
#define
GD_FLG_SILENT0x00004      /*Silent mode */
#define GD_FLG_POSTFAIL 0x00008
  /*Critical POST test failed */

#define GD_FLG_POSTSTOP 0x00010  /*POST seqeunce aborted */

#define GD_FLG_LOGINIT 0x00020    /*Log Buffer has been initialized */

#defineGD_FLG_DISABLE_CONSOLE 0x00040 /*Disable console (in & out) */
#defineDECLARE_GLOBAL_DATA_PTR register volatile gd_t *gd asm ("r8")


2.bd_t:board info数据结构定义,位于文件include/asm-arm/u-boot.h。保存板子参数。


typedefstruct bd_info {
int
bi_baudrate;                    //
串口波特率
unsigned long
bi_ip_addr;    //IP
地址
struct environment_s
*bi_env;
ulong
bi_arch_number;        //
板子ID
ulong
bi_boot_params;         //
启动参数
struct
                                  //DRAM BANKS
配置,起始地址与长度
{
ulong
start;
ulong
size;
}bi_dram[CONFIG_NR_DRAM_BANKS];
} bd_t;