Start of u-boot_ Armboot analysis (II)

• This article mainly analyzes init_sequence Initialization function in

board_init

int board_init(void)
{
    
	DECLARE_GLOBAL_DATA_PTR;
#ifdef CONFIG_DRIVER_SMC911X
	smc9115_pre_init();
#endif

#ifdef CONFIG_DRIVER_DM9000
	dm9000_pre_init();
#endif

	gd->bd->bi_arch_number = MACH_TYPE;
	gd->bd->bi_boot_params = (PHYS_SDRAM_1+0x100);

	return 0;
}

• It only defines CONFIG_DRIVER_DM9000, Therefore, the main work focuses on dm9000 On the network card device
• dm9000_pre_init The function is mainly for the network card GPIO And port configuration
• gd->bd->bi_arch_number Machine code , Is the unique identifier for configuring the development board . The main function of machine code is to uboot and Linux Comparison and adaptation between kernels .uboot This machine code will be passed to the kernel as part of the parameter when the kernel is started , Only when they are the same can they be started normally
• gd->bd->bi_boot_params Express uboot to Linux The memory address of the parameter passed during kernel startup , The address defined here is 0x30000100

interrupt_init

int interrupt_init(void)
{
    

	S5PC11X_TIMERS *const timers = S5PC11X_GetBase_TIMERS();

	/* use PWM Timer 4 because it has no output */
	/* prescaler for Timer 4 is 16 */
	timers->TCFG0 = 0x0f00;
	if (timer_load_val == 0) {
    
		/* * for 10 ms clock period @ PCLK with 4 bit divider = 1/2 * (default) and prescaler = 16. Should be 10390 * @33.25MHz and @ 66 MHz */
		timer_load_val = get_PCLK() / (16 * 100);
	}
	/* load value for 10 ms timeout */
	lastdec = timers->TCNTB4 = timer_load_val;
	/* auto load, manual update of Timer 4 */
	timers->TCON = (timers->TCON & ~0x00700000) | TCON_4_AUTO | TCON_4_UPDATE;
	/* auto load, start Timer 4 */
	timers->TCON = (timers->TCON & ~0x00700000) | TCON_4_AUTO | COUNT_4_ON;
	timestamp = 0;

	return (0);
}

• Function to initialize timer

env_init

• Initialize environment variables
• This function can be found in many places , Respectively in env_xxx.c In file . Checked , This development board uses env_init Function in env_movi.c in
• This function is only for the in memory env Initialization and determination are made (gd->env_valid), Currently, there is no environment variable from SD Card to DDR Repositioning in , Therefore, the current environment variable cannot be used
• start_armboot Function is executing env_relocate After that, the environment variables are changed from SD In the card DDR Repositioning in . Only when environment variables are needed after relocation can you start from DDR To get in , Before relocation, you can only use environment variables from SD Read from the card

init_baudrate

static int init_baudrate (void)
{
    
	char tmp[64];	/* long enough for environment variables */
	int i = getenv_r ("baudrate", tmp, sizeof (tmp));
	gd->bd->bi_baudrate = gd->baudrate = (i > 0)
			? (int) simple_strtoul (tmp, NULL, 10)
			: CONFIG_BAUDRATE;

	return (0);
}

• This function sets the baud rate of the serial port
• First, get the... In the environment variable baudrate value , If it works , Then use this value as an environment variable to record in gd->bd->bi_baudrate and gd->baudrate in , Otherwise use CONFIG_BAUDRATE Defined value

console_init_f

• Perform the first stage initialization of the console
• Just right gd->have_console The assignment is 1

dram_init

int dram_init(void)
{
    
	DECLARE_GLOBAL_DATA_PTR;

	gd->bd->bi_dram[0].start = PHYS_SDRAM_1;
	gd->bd->bi_dram[0].size = PHYS_SDRAM_1_SIZE;

#if defined(PHYS_SDRAM_2)
	gd->bd->bi_dram[1].start = PHYS_SDRAM_2;
	gd->bd->bi_dram[1].size = PHYS_SDRAM_2_SIZE;
#endif

#if defined(PHYS_SDRAM_3)
	gd->bd->bi_dram[2].start = PHYS_SDRAM_3;
	gd->bd->bi_dram[2].size = PHYS_SDRAM_3_SIZE;
#endif

	return 0;
}

• Yes DDR Initialize the software
• Tell the software DDR Starting address and length of

display_dram_config

• Print ram Configuration information
• stay uboot Using the command line of bdinfo You can print it out gd->bd All hardware related global variable values recorded in , You can get DDR Configuration information