u-boot transplant summary (IV) u-boot-2010.09 framework analysis

1. This porting is based on FL2440. The basic hardware of the board is:

(II) The overall framework of U-Boot:

The files marked in red are more important and are the main files to be modified.

(III) This time, u-boot-2010.09 is modified based on the FL2440 board, and the second stage initialization function analysis

1. Testing

Add board configuration in the boards.cfg file

Makefile adds the cross compiler buildroot-2011.11

Test compilation, make ly2440_config read the configuration file

Since Samsung's smdk2410 is very similar to s3c2440, we use smdk2410 as a model to improve the efficiency of code modification

[zhouguangfeng@centos6 u-boot-2010.09]$ cd board
[zhouguangfeng@centos6 board] $mkdir -p lingyun/ly2
[zhouguangfeng@centos6 board]$ cp samsung/smdk2410/* lingyun/ly2440
[zhouguangfeng@centos6 board]$ ls lingyun/ly2440
config.mk  flash.c  lowlevel_init.S  Makefile  smdk2410.c
[zhouguangfeng@centos6 board] $mv Lingyuan/ly2440/smdk2410.c Lingyuan/ly2440/ly2440.c
[zhouguangfeng@centos6 board]$ ls lingyun/ly2440
config.mk  flash.c  lowlevel_init.S  ly2440.c  Makefile
[zhouguangfeng@centos6 board]$ 

The specific changes are not detailed.

2. U-Boot starts, and the first execution is Start.S. There is a summary in the u-boot transplant summary (I) start.S analysis (click link). Here are some functions about the second stage of board initialization: U-Boot uses an array init_sequence to store function pointers of initialization functions that must be executed for most development boards. There are many compilation options in the init_sequence array. After removing the compilation options, the init_sequence array is as follows:

typedef int(init_fnc_t) (void); //declare a function type, return value int, parameter void

init_fnc_t*init_sequence[] = {

board_init, /*Development board related configuration --board/lingyun/ly2440/ly2440.c */

timer_init, /*Clock initialization--arch/arm/cpu/arm920t/s3c24x0/timer.c*/

env_init, /*Initialize environment variables--common/env_flash.c or common/env_nand.c*/

init_baudrate, /*Initialize baud rate -- arch/arm/lib/board.c */

serial_init, /*Serial port initialization--drivers/serial/serial_s3c24x0.c*/

console_init_f, /* Control communication station initialization phase 1 -- common/console.c */

display_banner, /*Print U-Boot version, compilation time -- arch/arm/lib/board.c */

dram_init, /*Configure available RAM--board/lingyun/ly2440/ly2440.c */

display_dram_config, /* Display RAM size -- arch/arm/lib/board.c*/

NULL,

};

The board_init function is defined in board/lingyun/ly2440/ly2440.c. This function sets the values ​​of MPLLCOM, UPLLCON, and some GPIO registers, as well as the U-Boot machine code and kernel startup parameter addresses:

#if defined(CONFIG_S3C2410)

/* arch number of SMDK2410-Board */
gd->bd->bi_arch_number = MACH_TYPE_SMDK2410;
#endif

#if defined(CONFIG_S3C2440)

/* arch number of S3C2440-Board ,MINI2440 machine code*/
gd->bd->bi_arch_number = MACH_TYPE_MINI2440 ;
#endif

/* Kernel startup parameter address */

gd->bd->bi_boot_params=0x30000100;

FL2440 uses two 32MB SDRAMs to form a 64MB memory, connected to BANK6 of the memory controller, with an address space of 0x3000 0000~0x3400 0000. In include/configs/ly2440.h, PHYS_SDRAM_1 and PHYS_SDRAM_1_SIZE are defined as 0x30000000 and 0x04000000 (64M) respectively.

The dram_init function is defined in board/lingyun/ly2440/ly2440.c as follows:

int dram_init (void)

{

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

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

return 0;

}

After analyzing the above data structure, let's analyze the start_armboot function:

voidstart_armboot (void)

{

init_fnc_t**init_fnc_ptr;

char *s;

… …

/* Calculate the address of the global data structure gd, defined in include/asm/global_data.h */

gd =(gd_t*)(_armboot_start - CONFIG_SYS_MALLOC_LEN - sizeof(gd_t));

… …

memset((void*)gd, 0, sizeof (gd_t));

gd->bd= (bd_t*)((char*)gd - sizeof(bd_t)); /*bd structure is defined in arch/arm/include/asm/u-boot.h, saves information about the board*/

memset(gd->bd, 0, sizeof (bd_t));

gd->flags|= GD_FLG_RELOC;

monitor_flash_len= _bss_start - _armboot_start;

/* Call the initialization functions in the init_sequence array one by one */

for(init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {

if((*init_fnc_ptr)() != 0) {

hang();

}

}

/*armboot_start is initialized in arch/arm/cpu/arm920t/start.S as _start in the u-boot.lds linker script */

mem_malloc_init(_armboot_start - CONFIG_SYS_MALLOC_LEN,

CONFIG_SYS_MALLOC_LEN);

/* NAND Flash initialization */

#ifdefined(CONFIG_CMD_NAND)

puts("NAND:  ");

nand_init();        /* go init the NAND */

#endif

… …

/*Configure environment variables, relocate */

env_relocate();

… …

/* Get the IP address from the environment variable */

gd->bd->bi_ip_addr= getenv_IPaddr ("ipaddr");

stdio_init(); /* get the devices list going. */

jumptable_init();

… …

console_init_r(); /* fully init console as a device */

… …

/* enableexceptions */

enable_interrupts();

#ifdefCONFIG_USB_DEVICE

usb_init_slave();

#endif

/* Initialize from environment*/

if ((s =getenv ("loadaddr")) != NULL) {

load_addr= simple_strtoul (s, NULL, 16);

}

#ifdefined(CONFIG_CMD_NET)

if ((s =getenv ("bootfile")) != NULL) {

copy_filename(BootFile, s, sizeof (BootFile));

}

#endif

… …

/*Network card initialization */

#ifdefined(CONFIG_CMD_NET)

#ifdefined(CONFIG_NET_MULTI)

puts("Net:   ");

#endif

eth_initialize(gd->bd);

#if defined(CONFIG_RESET_PHY_R)
debug ("Reset Ethernet PHYn");
reset_phy();
#endif

#endif

/*main_loop() can return to retry autoboot, if so just run it again. */

for (;;){

main_loop();

}

/*NOTREACHED - no way out of command loop except booting */

}

The main_loop function is defined in common/main.c. In general, when entering the main_loop function, the CONFIG_BOOTDELAY defined in include/configs/ly2440.h is exceeded.

time without pressing ESC, U-Boot will load the system kernel.