uboot入口
arch/arm/lib/crt0.S
#include <config.h>
#include <asm-offsets.h>
#include <linux/linkage.h>
/*
* This file handles the target-independent stages of the U-Boot
* start-up where a C runtime environment is needed. Its entry point
* is _main and is branched into from the target's start.S file.
*
* _main execution sequence is:
*
* 1. Set up initial environment for calling board_init_f().
* This environment only provides a stack and a place to store
* the GD ('global data') structure, both located in some readily
* available RAM (SRAM, locked cache...). In this context, VARIABLE
* global data, initialized or not (BSS), are UNAVAILABLE; only
* CONSTANT initialized data are available.
*
* 2. Call board_init_f(). This function prepares the hardware for
* execution from system RAM (DRAM, DDR...) As system RAM may not
* be available yet, , board_init_f() must use the current GD to
* store any data which must be passed on to later stages. These
* data include the relocation destination, the future stack, and
* the future GD location.
*
* (the following applies only to non-SPL builds)
*
* 3. Set up intermediate environment where the stack and GD are the
* ones allocated by board_init_f() in system RAM, but BSS and
* initialized non-const data are still not available.
*
* 4. Call relocate_code(). This function relocates U-Boot from its
* current location into the relocation destination computed by
* board_init_f().
*
* 5. Set up final environment for calling board_init_r(). This
* environment has BSS (initialized to 0), initialized non-const
* data (initialized to their intended value), and stack in system
* RAM. GD has retained values set by board_init_f(). Some CPUs
* have some work left to do at this point regarding memory, so
* call c_runtime_cpu_setup.
*
* 6. Branch to board_init_r().
*/
/*
* entry point of crt0 sequence
*/
ENTRY(_main)
/*
* Set up initial C runtime environment and call board_init_f(0).
*/
#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
ldr sp, =(CONFIG_SPL_STACK)
#else
ldr sp, =(CONFIG_SYS_INIT_SP_ADDR)
#endif
bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
mov r2, sp
sub sp, sp, #GD_SIZE /* allocate one GD above SP */
bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
mov r9, sp /* GD is above SP */
mov r1, sp
mov r0, #0
clr_gd:
cmp r1, r2 /* while not at end of GD */
strlo r0, [r1] /* clear 32-bit GD word */
addlo r1, r1, #4 /* move to next */
blo clr_gd
#if defined(CONFIG_SYS_MALLOC_F_LEN)
sub sp, sp, #CONFIG_SYS_MALLOC_F_LEN
str sp, [r9, #GD_MALLOC_BASE]
#endif
/* mov r0, #0 not needed due to above code */
bl board_init_f
#if ! defined(CONFIG_SPL_BUILD)
/*
* Set up intermediate environment (new sp and gd) and call
* relocate_code(addr_moni). Trick here is that we'll return
* 'here' but relocated.
*/
ldr sp, [r9, #GD_START_ADDR_SP] /* sp = gd->start_addr_sp */
bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
ldr r9, [r9, #GD_BD] /* r9 = gd->bd */
sub r9, r9, #GD_SIZE /* new GD is below bd */
adr lr, here
ldr r0, [r9, #GD_RELOC_OFF] /* r0 = gd->reloc_off */
add lr, lr, r0
ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */
b relocate_code
here:
/*
* now relocate vectors
*/
bl relocate_vectors
/* Set up final (full) environment */
bl c_runtime_cpu_setup /* we still call old routine here */
#endif
#if !defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_FRAMEWORK)
# ifdef CONFIG_SPL_BUILD
/* Use a DRAM stack for the rest of SPL, if requested */
bl spl_relocate_stack_gd
cmp r0, #0
movne sp, r0
# endif
ldr r0, =__bss_start /* this is auto-relocated! */
#ifdef CONFIG_USE_ARCH_MEMSET
ldr r3, =__bss_end /* this is auto-relocated! */
mov r1, #0x00000000 /* prepare zero to clear BSS */
subs r2, r3, r0 /* r2 = memset len */
bl memset
#else
ldr r1, =__bss_end /* this is auto-relocated! */
mov r2, #0x00000000 /* prepare zero to clear BSS */
clbss_l:cmp r0, r1 /* while not at end of BSS */
strlo r2, [r0] /* clear 32-bit BSS word */
addlo r0, r0, #4 /* move to next */
blo clbss_l
#endif
#if ! defined(CONFIG_SPL_BUILD)
bl coloured_LED_init
bl red_led_on
#endif
/* call board_init_r(gd_t *id, ulong dest_addr) */
mov r0, r9 /* gd_t */
ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */
/* call board_init_r */
ldr pc, =<span style="color:#FF0000;">board_init_r</span> /* this is auto-relocated! */
/* we should not return here. */
#endif
board/freescale/mx6sabresd下的mx6sabresd.c
void board_init_f(ulong dummy)
{
/* setup AIPS and disable watchdog */
arch_cpu_init();
ccgr_init();
gpr_init();
/* iomux and setup of i2c */
board_early_init_f();
/* setup GP timer */
timer_init();
/* UART clocks enabled and gd valid - init serial console */
preloader_console_init();
/* DDR initialization */
spl_dram_init();
/* Clear the BSS. */
memset(__bss_start, 0, __bss_end - __bss_start);
/* load/boot image from boot device */
<span style="color:#FF0000;">board_init_r(NULL, 0);</span>
}
函数board_init_r(NULL, 0)最终调用了arch/arm/lib/board.c
void board_init_r(gd_t *id, ulong dest_addr)
{
ulong malloc_start;
#if !defined(CONFIG_SYS_NO_FLASH)
ulong flash_size;
#endif
gd->flags |= GD_FLG_RELOC; /* tell others: relocation done */
bootstage_mark_name(BOOTSTAGE_ID_START_UBOOT_R, "board_init_r");
monitor_flash_len = (ulong)&__rel_dyn_end - (ulong)_start;
/* Enable caches */
enable_caches();
debug("monitor flash len: %08lX\n", monitor_flash_len);
board_init(); /* Setup chipselects */
/*
* TODO: printing of the clock inforamtion of the board is now
* implemented as part of bdinfo command. Currently only support for
* davinci SOC's is added. Remove this check once all the board
* implement this.
*/
#ifdef CONFIG_CLOCKS
set_cpu_clk_info(); /* Setup clock information */
#endif
serial_initialize();
debug("Now running in RAM - U-Boot at: %08lx\n", dest_addr);
#ifdef CONFIG_LOGBUFFER
logbuff_init_ptrs();
#endif
#ifdef CONFIG_POST
post_output_backlog();
#endif
/* The Malloc area is immediately below the monitor copy in DRAM */
malloc_start = dest_addr - TOTAL_MALLOC_LEN;
mem_malloc_init (malloc_start, TOTAL_MALLOC_LEN);
#ifdef CONFIG_ARCH_EARLY_INIT_R
arch_early_init_r();
#endif
power_init_board();
#if !defined(CONFIG_SYS_NO_FLASH)
puts("Flash: ");
flash_size = flash_init();
if (flash_size > 0) {
# ifdef CONFIG_SYS_FLASH_CHECKSUM
print_size(flash_size, "");
/*
* Compute and print flash CRC if flashchecksum is set to 'y'
*
* NOTE: Maybe we should add some WATCHDOG_RESET()? XXX
*/
if (getenv_yesno("flashchecksum") == 1) {
printf(" CRC: %08X", crc32(0,
(const unsigned char *) CONFIG_SYS_FLASH_BASE,
flash_size));
}
putc('\n');
# else /* !CONFIG_SYS_FLASH_CHECKSUM */
print_size(flash_size, "\n");
# endif /* CONFIG_SYS_FLASH_CHECKSUM */
} else {
puts(failed);
hang();
}
#endif
#if defined(CONFIG_CMD_NAND)
puts("NAND: ");
nand_init(); /* go init the NAND */
#endif
#if defined(CONFIG_CMD_ONENAND)
onenand_init();
#endif
#ifdef CONFIG_GENERIC_MMC
puts("MMC: ");
mmc_initialize(gd->bd);
#endif
#ifdef CONFIG_CMD_SCSI
puts("SCSI: ");
scsi_init();
#endif
#ifdef CONFIG_HAS_DATAFLASH
AT91F_DataflashInit();
dataflash_print_info();
#endif
/* initialize environment */
if (should_load_env())
env_relocate();
else
set_default_env(NULL);
#if defined(CONFIG_CMD_PCI) || defined(CONFIG_PCI)
arm_pci_init();
#endif
<span style="color:#FF0000;">stdio_init(); /* get the devices list going. */</span>
jumptable_init();
#if defined(CONFIG_API)
/* Initialize API */
api_init();
#endif
console_init_r(); /* fully init console as a device */
#ifdef CONFIG_DISPLAY_BOARDINFO_LATE
# ifdef CONFIG_OF_CONTROL
/* Put this here so it appears on the LCD, now it is ready */
display_fdt_model(gd->fdt_blob);
# else
checkboard();
# endif
#endif
#if defined(CONFIG_ARCH_MISC_INIT)
/* miscellaneous arch dependent initialisations */
arch_misc_init();
#endif
#if defined(CONFIG_MISC_INIT_R)
/* miscellaneous platform dependent initialisations */
misc_init_r();
#endif
/* set up exceptions */
interrupt_init();
/* enable exceptions */
enable_interrupts();
/* Initialize from environment */
load_addr = getenv_ulong("loadaddr", 16, load_addr);
#ifdef CONFIG_BOARD_LATE_INIT
board_late_init();
#endif
#ifdef CONFIG_FSL_FASTBOOT
fastboot_setup();
#endif
#ifdef CONFIG_BITBANGMII
bb_miiphy_init();
#endif
#if defined(CONFIG_CMD_NET)
puts("Net: ");
eth_initialize(gd->bd);
#if defined(CONFIG_RESET_PHY_R)
debug("Reset Ethernet PHY\n");
reset_phy();
#endif
#endif
#ifdef CONFIG_POST
post_run(NULL, POST_RAM | post_bootmode_get(0));
#endif
#if defined(CONFIG_PRAM) || defined(CONFIG_LOGBUFFER)
/*
* Export available size of memory for Linux,
* taking into account the protected RAM at top of memory
*/
{
ulong pram = 0;
uchar memsz[32];
#ifdef CONFIG_PRAM
pram = getenv_ulong("pram", 10, CONFIG_PRAM);
#endif
#ifdef CONFIG_LOGBUFFER
#ifndef CONFIG_ALT_LB_ADDR
/* Also take the logbuffer into account (pram is in kB) */
pram += (LOGBUFF_LEN + LOGBUFF_OVERHEAD) / 1024;
#endif
#endif
sprintf((char *)memsz, "%ldk", (gd->ram_size / 1024) - pram);
setenv("mem", (char *)memsz);
}
#endif
#ifdef CONFIG_FSL_FASTBOOT
check_fastboot();
#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 */
}
这里重点研究一下stdio_init()函数，在函数在common/stdio.c中实现
int stdio_init(void)
{
stdio_init_tables();
<span style="color:#FF0000;">stdio_add_devices();</span>
return 0;
}
int stdio_add_devices(void)
{
#ifdef CONFIG_SYS_I2C
i2c_init_all();
#else
#if defined(CONFIG_HARD_I2C)
i2c_init (CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);
#endif
#endif
#ifdef CONFIG_LCD
drv_lcd_init ();
#endif
#if defined(CONFIG_VIDEO) || defined(CONFIG_CFB_CONSOLE)
<span style="color:#FF0000;">drv_video_init ();</span>
#endif
#ifdef CONFIG_KEYBOARD
drv_keyboard_init ();
#endif
#ifdef CONFIG_LOGBUFFER
drv_logbuff_init ();
#endif
drv_system_init ();
serial_stdio_init ();
#ifdef CONFIG_USB_TTY
drv_usbtty_init ();
#endif
#ifdef CONFIG_NETCONSOLE
drv_nc_init ();
#endif
#ifdef CONFIG_JTAG_CONSOLE
drv_jtag_console_init ();
#endif
#ifdef CONFIG_CBMEM_CONSOLE
cbmemc_init();
#endif
return 0;
}
int drv_video_init(void)
{
int skip_dev_init;
struct stdio_dev console_dev;
/* Check if video initialization should be skipped */
<span style="color:#FF0000;">if (board_video_skip())</span>
return 0;
/* Init video chip - returns with framebuffer cleared */
<span style="color:#FF0000;">skip_dev_init = (video_init() == -1);</span>
if (board_cfb_skip())
return 0;
#if !defined(CONFIG_VGA_AS_SINGLE_DEVICE)
debug("KBD: Keyboard init ...\n");
skip_dev_init |= (VIDEO_KBD_INIT_FCT == -1);
#endif
if (skip_dev_init)
return 0;
/* Init vga device */
memset(&console_dev, 0, sizeof(console_dev));
strcpy(console_dev.name, "vga");
console_dev.ext = DEV_EXT_VIDEO; /* Video extensions */
console_dev.flags = DEV_FLAGS_OUTPUT | DEV_FLAGS_SYSTEM;
console_dev.putc = video_putc; /* 'putc' function */
console_dev.puts = video_puts; /* 'puts' function */
#if !defined(CONFIG_VGA_AS_SINGLE_DEVICE)
/* Also init console device */
console_dev.flags |= DEV_FLAGS_INPUT;
console_dev.tstc = VIDEO_TSTC_FCT; /* 'tstc' function */
console_dev.getc = VIDEO_GETC_FCT; /* 'getc' function */
#endif /* CONFIG_VGA_AS_SINGLE_DEVICE */
if (stdio_register(&console_dev) != 0)
return 0;
/* Return success */
return 1;
}
board_video_skip获取要初始化的屏幕参数arch/arm/imx-common/video.c
int board_video_skip(void)
{
int i;
int ret;
char const *panel = getenv("panel");
if (!panel) {
for (i = 0; i < display_count; i++) {
struct display_info_t const *dev = displays+i;
if (dev->detect && dev->detect(dev)) {
panel = dev->mode.name;
printf("auto-detected panel %s\n", panel);
break;
}
}
if (!panel) {
panel = displays[0].mode.name;
printf("No panel detected: default to %s\n", panel);
i = 2;
}
} else {
for (i = 0; i < display_count; i++) {
if (!strcmp(panel, displays[i].mode.name))
break;
}
}
if (i < display_count) {
ret = <span style="color:#FF0000;">ipuv3_fb_init</span>(&displays[i].mode, 0,
displays[i].pixfmt);
if (!ret) {
if (displays[i].enable)
displays[i].enable(displays + i);
printf("Display: %s (%ux%u)\n",
displays[i].mode.name,
displays[i].mode.xres,
displays[i].mode.yres);
} else
printf("LCD %s cannot be configured: %d\n",
displays[i].mode.name, ret);
} else {
printf("unsupported panel %s\n", panel);
return -EINVAL;
}
return 0;
最终调用video_init初始化屏幕并显示logo
void video_inti(void)
{
------
video_hw_init //屏幕初始化(根据上面获取到的参数)
video_logo();//刷logo(位于tools/logos/xxx.bmp,该bmp位图被编译成数组，最终被刷出来)
------
}
在刷logo的过程中会调用flush_cache刷新一下缓冲区，否则图像会变得离散。
if (cfb_do_flush_cache)
flush_cache(VIDEO_FB_ADRS, VIDEO_SIZE)；
VIDEO_FB_ADRS显示基地址
VIDEO_SIZE显示的大小
在uboot中有很多debug函数，打开debug函数可以看到uboot中函数的调用过程。
dedug函数(include/common.h)的定义为
#ifdef DEBUG
#define _DEBUG 1
#else
#define _DEBUG 0
#endif
#ifndef pr_fmt
#define pr_fmt(fmt) fmt
#endif
/*
* Output a debug text when condition "cond" is met. The "cond" should be
* computed by a preprocessor in the best case, allowing for the best
* optimization.
*/
#define debug_cond(cond, fmt, args...) do { if (cond) printf(pr_fmt(fmt), ##args); } while (0)
#define debug(fmt, args...) debug_cond(_DEBUG, fmt, ##args)
只需在前面添加#define DEBUG即可打开该函数。
另外,查找函数调用关系时，如果有多个地方被定义，不确定具体的定义位置时，只需到该目录下，ls -al *.o，即可确认真正被调用的函数。因为该函数被编译了，就会
生成.o文件。
时间： 2024-11-09 00:45:29