Exynos4412 Uboot 移植（六）—— 相关知识补充

Uboot版本：u-boot-2013.01

一、gd结构体的定义与使用

gd_t 和 bd_t 是u-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。

gd_t 定义在/u-boot-2013.01/arch/arm/include/asm/global_data.h

bd_t 定义在 ./include/asm-arm/u-boot.h

1、gd_t : global data数据结构定义

位于文件/u-boot-2013.01/arch/arm/include/asm/global_data.h 中。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

从这个宏的定义可以看出，gd是一个保存在ARM的r8寄存器中的gd_t结构体的指针。指定占用寄存器R8。

typedef struct global_data {

bd_t *bd;//struct board_info指针，保存开发板信息

unsigned long flags;//指示标志，如设备已经初始化标志等

unsigned int baudrate;//串口波特率

unsigned long have_console; //串口初始化标志

#ifdef CONFIG_PRE_CONSOLE_BUFFER

unsigned long precon_buf_idx; /* Pre-Console buffer index */

#endif

unsigned long env_addr; /* Address  of Environment struct */

unsigned long env_valid; /* Checksum of Environment valid? */

unsigned long fb_base; /* base address of frame buffer */

#ifdef CONFIG_FSL_ESDHC

unsigned long sdhc_clk;

#endif

#ifdef CONFIG_AT91FAMILY

/* "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

/* "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

#ifdef CONFIG_IXP425

unsigned long timestamp;

#endif

unsigned long relocaddr; /* Start address of U-Boot in RAM */

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_ICACHE_OFF) && defined(CONFIG_SYS_DCACHE_OFF))

unsigned long tlb_addr;

unsigned long tlb_size;

#endif

const void *fdt_blob; /* Our device tree, NULL if none */

void **jt; /* jump table */

char env_buf[32]; /* buffer for getenv() before reloc. */

#if defined(CONFIG_POST) || defined(CONFIG_LOGBUFFER)

unsigned long post_log_word; /* Record POST activities */

unsigned long post_log_res; /* success of POST test */

unsigned long post_init_f_time; /* When post_init_f started */

#endif

} gd_t;

2.、bd_t :board info数据结构定义

位于文件u-boot-2013.01/arch/arm/include/asm/u-boot.h。保存板子参数。

typedef struct bd_info {

unsigned int bi_baudrate; /* 串口波特率 */

    ulong         bi_arch_number; /* 开发板机器ID */

    ulong         bi_boot_params; /* 启动参数 */

unsigned long bi_arm_freq; /* arm frequency */

unsigned long bi_dsp_freq; /* dsp core frequency */

unsigned long bi_ddr_freq; /* ddr frequency */

    struct /* RAM configuration */

    {

ulong start;

ulong size;

    } bi_dram[CONFIG_NR_DRAM_BANKS];

} bd_t;