u-boot下的两个重要数据：bd_t和gd_t

[u-boot: v2013.04]

[Author: Bo Shen <voice.shen@gmail.com>]

众所周知，u-boot中有两个重要数据结构，一个是bd_t，另外一个是gd_t。下面分别介绍这两个数据结构。

1. bd_t

此数据结构保存board相关的信息。

定义：<arch/arm/include/asm/u-boot.h>

其具体结构如下：

typedef struct bd_info {
	unsigned int	bi_baudrate;	/* serial console baudrate */
        ulong	        bi_arch_number;	/* unique id for this board */
        ulong	        bi_boot_params;	/* where this board expects params */
	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;

2. gd_t

定义：<include/asm-generic/global_data.h>

其具体结构如下：

typedef struct global_data {
	bd_t *bd;
	unsigned long flags;
	unsigned int baudrate;
	unsigned long cpu_clk;	/* CPU clock in Hz!		*/
	unsigned long bus_clk;
	/* We cannot bracket this with CONFIG_PCI due to mpc5xxx */
	unsigned long pci_clk;
	unsigned long mem_clk;
#if defined(CONFIG_LCD) || defined(CONFIG_VIDEO)
	unsigned long fb_base;	/* Base address of framebuffer mem */
#endif
#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
#ifdef CONFIG_BOARD_TYPES
	unsigned long board_type;
#endif
	unsigned long have_console;	/* serial_init() was called */
#ifdef CONFIG_PRE_CONSOLE_BUFFER
	unsigned long precon_buf_idx;	/* Pre-Console buffer index */
#endif
#ifdef CONFIG_MODEM_SUPPORT
	unsigned long do_mdm_init;
	unsigned long be_quiet;
#endif
	unsigned long env_addr;	/* Address  of Environment struct */
	unsigned long env_valid;	/* Checksum of Environment valid? */

	/* TODO: is this the same as relocaddr, or something else? */
	unsigned long dest_addr;	/* Post-relocation address of U-Boot */
	unsigned long dest_addr_sp;
	unsigned long ram_top;	/* Top address of RAM used by U-Boot */

	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;
	struct global_data *new_gd;	/* relocated global data */
	const void *fdt_blob;	/* Our device tree, NULL if none */
	void *new_fdt;		/* Relocated FDT */
	unsigned long fdt_size;	/* Space reserved for relocated FDT */
	void **jt;		/* jump table */
	char env_buf[32];	/* buffer for getenv() before reloc. */
	struct arch_global_data arch;	/* architecture-specific data */
} gd_t;

这其中还包含了一个arch_global_data，对于ARM,这个结构体定义在：<arch/arm/include/asm/global_data.h>