最近给Exynos 4412开发板移植了uboot，具体过程就不表了，可以参考： http://blog.csdn.net/abcamus/article/details/51326881
代码都已经上传到github： https://github.com/abcamus/bootloader-for-Exynos-4412.git
有什么问题欢迎联系博主。
几个注意点：
1. arch/arm/include/asm/arch-exynos/power.h中的结构体定义
和手册上的有点出入，属于版本兼容问题，根据手册改改，我是一个个对的，花了几个小时时间，还担心哪里出错，汗！。示例如下：
struct exynos4x12_power {
unsigned int om_stat;
unsigned char res1[0xc];
unsigned int rtc_clko_sel; // 0x10
unsigned int gnss_rtc_out_ctrl; // 0x14
unsigned char res2[0x1e8]; // 0x18
unsigned int central_seq_config; // 0x200
unsigned int res3;
unsigned int central_seq_option; // 0x208
unsigned char res4[0x1f4]; // 0x20c
...
};2. 时钟的寄存器映射
和power.h同目录下的clock.h
struct exynos4x12_clock {
unsigned char res1[0x4200];
unsigned int src_leftbus; // 0x4200
unsigned char res2[0x1fc]; // 0x4204
unsigned int mux_stat_leftbus; // 0x4400
unsigned char res3[0xfc]; // 0x4404
unsigned int div_leftbus; // 0x4500
unsigned char res4[0xfc];
unsigned int div_stat_leftbus; // 0x4600
unsigned char res5[0x1fc];
...
};3. 几个宏
arch/arm/include/asm/arch-exynos/cpu.h
因为tag追踪不到这些地方，所以记录在这里，方便查询。
#define SAMSUNG_BASE(device, base) \
static inline unsigned int __attribute__((no_instrument_function)) \
samsung_get_base_##device(void) \
{ \
if (cpu_is_exynos4()) { \
if (proid_is_exynos4412()) \
return EXYNOS4X12_##base; \
return EXYNOS4_##base; \
} else if (cpu_is_exynos5()) { \
if (proid_is_exynos5420() || proid_is_exynos5800()) \
return EXYNOS5420_##base; \
return EXYNOS5_##base; \
} \
return 0; \
}
SAMSUNG_BASE(adc, ADC_BASE)
SAMSUNG_BASE(clock, CLOCK_BASE)
SAMSUNG_BASE(ace_sfr, ACE_SFR_BASE)
SAMSUNG_BASE(dp, DP_BASE)
SAMSUNG_BASE(sysreg, SYSREG_BASE)
SAMSUNG_BASE(fimd, FIMD_BASE)
SAMSUNG_BASE(i2c, I2C_BASE)
SAMSUNG_BASE(i2s, I2S_BASE)
SAMSUNG_BASE(mipi_dsim, MIPI_DSIM_BASE)
SAMSUNG_BASE(gpio_part1, GPIO_PART1_BASE)
SAMSUNG_BASE(gpio_part2, GPIO_PART2_BASE)
SAMSUNG_BASE(gpio_part3, GPIO_PART3_BASE)
SAMSUNG_BASE(gpio_part4, GPIO_PART4_BASE)
SAMSUNG_BASE(pro_id, PRO_ID)
SAMSUNG_BASE(mmc, MMC_BASE)
SAMSUNG_BASE(modem, MODEM_BASE)
SAMSUNG_BASE(sromc, SROMC_BASE)
SAMSUNG_BASE(swreset, SWRESET)
SAMSUNG_BASE(timer, PWMTIMER_BASE)
SAMSUNG_BASE(uart, UART_BASE)
SAMSUNG_BASE(usb_phy, USBPHY_BASE)
SAMSUNG_BASE(usb3_phy, USB3PHY_BASE)
SAMSUNG_BASE(usb_ehci, USB_HOST_EHCI_BASE)
SAMSUNG_BASE(usb_xhci, USB_HOST_XHCI_BASE)
SAMSUNG_BASE(usb_otg, USBOTG_BASE)
SAMSUNG_BASE(watchdog, WATCHDOG_BASE)
SAMSUNG_BASE(power, POWER_BASE)
SAMSUNG_BASE(spi, SPI_BASE)
SAMSUNG_BASE(spi_isp, SPI_ISP_BASE)
SAMSUNG_BASE(tzpc, TZPC_BASE)
SAMSUNG_BASE(dmc_ctrl, DMC_CTRL_BASE)
SAMSUNG_BASE(dmc_phy, DMC_PHY_BASE)
SAMSUNG_BASE(dmc_tzasc, DMC_TZASC_BASE)
SAMSUNG_BASE(audio_ass, AUDIOSS_BASE)4. board_init_f
arch/arm/cpu/armv7/exynos/spl_boot.c
在do_lowlevel_init中，arch_cpu_init会读取cpu id保存到全局变量中，samsung_get_base_*系列宏会从保存的全局变量判断是那个cpu型号，从而确定模块基地址，如果arch_cpu_init出错，在原来的架构下肯定是不能正常工作的。
其实非常简单，就是初始化cpu和clock，然后拷贝uboot镜像到dram中，接着运行dram中的uboot，主要就是在调试这一段代码。
void board_init_f(unsigned long bootflag)
{
__aligned(8) gd_t local_gd;
__attribute__((noreturn)) void (*uboot)(void);
setup_global_data(&local_gd);
if (do_lowlevel_init())
power_exit_wakeup();
copy_uboot_to_ram();
/* Jump to U-Boot image */
uboot = (void *)CONFIG_SYS_TEXT_BASE;
(*uboot)();
/* Never returns Here */
}5. 点灯调试
最好在函数led_on入口把r0,r1压栈，返回前出栈，否则其他代码运行可能会受影响。
led_on:
ldr r0, =0x11000100
mov r1, #1
str r1, [r0]
ldr r0, =0x11000060
mov r1, #0
str r1, [r0]
ldr r0, =0x11000104
mov r1, #1
str r1, [r0]
ldr r0, =0x11000064
mov r0, #0
str r0, [r0]
bx lr在需要调试的地方，插入led_on()或者bl led_on。譬如要判断变量a是否等于2,可以这么写
if (a == 2)
led_on();6. 几个镜像说明
在$(srctree)/spl/下，$(board)-spl.bin其实是芯片手册中的BL1，按照芯片手册的说法，iROM负责读入BL1到SRAM，然后BL1初始化系统时钟和DRAM控制器，然后就可以加载操作系统了。没错，我们编译出来的这个镜像实实在在地做了这些事情。
但是另一份文档（Android_Exynos4412_iROM_Secure_Booting_Guide_Ver.1.00.00，标题赫然写着4212,所以个人觉得参考价值不大，直接参考芯片手册）的说法，iROM先加载BL1,然后BL1加载BL2,BL2加载OS或者FW。此时BL1和BL2都会做初始化时钟的工作，BL2其实是多余的，直接从BL1加载。这让我困惑了一段时间，而且网络上有提供三星的BL1（大小为8KB）的，估计这个BL1是先加载BL2到SRAM，而不是直接加载OS，故而有此变化。芯片手册是如下这么说的：
- iROM is placed in internal 64 KB ROM. It initializes basic system functions such as clock and stack.
- iROM loads BL1 image from a specific booting device to internal 256 KB SRAM. The booting device is
selected by Operating Mode (OM) pins. According to the secure boot key values, iROM may do an integrity
check on BL1 image. - BL1 initializes system clock, and DRAM controller. After initializing DRAM controller, it loads OS image from
the booting device to DRAM. According to the secure boot key values, BL1 can do an integrity check on the
OS image. - After the booting completes, BL1 jumps to the operating system.
总结下来就是两种方法（现在采用的是第一种方法）：
1. 利用官方提供的BL1,然后uboot编译的时候生成的镜像中产生BL2（负责配置时钟/dmc等，拷贝OS）。这个时候BL2可以通过spl/u-boot-spl.bin生成。
2. 直接生成BL1,就是说把spl/landrover-spl.bin改巴改巴，符合iROM的要求，然后执行这个BL1的时候就完成了相当于第一种方法BL2的功能。
7. spl内存映射
在编译出来的u-boot-spl镜像中，原来指定的代码段地址为
/* IROM Function Pointers Table */
u32 irom_ptr_table[] = {
[MMC_INDEX] = 0x02020030, /* iROM Function Pointer-SDMMC boot */
[EMMC44_INDEX] = 0x02020044, /* iROM Function Pointer-EMMC4.4 boot*/
[EMMC44_END_INDEX] = 0x02020048,/* iROM Function Pointer-EMMC4.4 end boot operation */
[SPI_INDEX] = 0x02020058, /* iROM Function Pointer-SPI boot */
[USB_INDEX] = 0x02020070, /* iROM Function Pointer-USB boot*/
};8. 编译选项
把Makefile中的KBUILD_CFLAGS += -O2改为
KBUILD_CFLAGS += -O0关闭调试信息，方便反汇编的时候看代码
#注释掉
KBUILD_CFLAGS += -g
KBUILD_AFLAGS += -g9 反汇编
$ arm-none-linux-gnueabi-objdump -D u-boot-spl > outfile-D出来de反汇编文件包含所有的sections
10. 使用
参考命令
$ make landrover_defconfig
$ ./build.sh
$ sudo ./mkuboot /dev/sdc11. 输出界面(补充)
OK
U-Boot 2015.04-gdcc0814-dirty (Dec 20 2016 - 15:24:03) for LANDROVER
CPU: Exynos4412@1000MHz
Model: landrover based on Exynos4412
DRAM: 1 GiB
WARNING: Caches not enabled
Pre-reloc malloc() used 0xdc bytes (0 KB)
Now running in RAM - U-Boot at: 7fe6e000
MMC: EXYNOS DWMMC: 0
dwmci_send_cmd: DATA ERROR!
*** Warning - bad CRC, using default environment
Hit any key to stop autoboot: 0
dwmci_send_cmd: DATA ERROR!
SD/MMC found on device 0
** File not found uEnv.txt **
** File not found boot.scr **
** File not found uImage **
Wrong Image Format for bootm command
ERROR: can't get kernel image!
LANDROVER #
LANDROVER #
LANDROVER # ?
? - alias for 'help'
base - print or set address offset
bdinfo - print Board Info structure
boot - boot default, i.e., run 'bootcmd'
bootd - boot default, i.e., run 'bootcmd'
bootelf - Boot from an ELF image in memory
bootm - boot application image from memory
bootvx - Boot vxWorks from an ELF image
bootz - boot Linux zImage image from memory
cmp - memory compare
coninfo - print console devices and information
cp - memory copy
crc32 - checksum calculation
dcache - enable or disable data cache
dfu - Device Firmware Upgrade
dm - Driver model low level access
echo - echo args to console
editenv - edit environment variable
env - environment handling commands
erase - erase FLASH memory
exit - exit script
ext2load- load binary file from a Ext2 filesystem
ext2ls - list files in a directory (default /)
ext4load- load binary file from a Ext4 filesystem
ext4ls - list files in a directory (default /)
ext4size- determine a file's size
ext4write- create a file in the root directory
false - do nothing, unsuccessfully
fatinfo - print information about filesystem
fatload - load binary file from a dos filesystem
fatls - list files in a directory (default /)
fatsize - determine a file's size
fatwrite- write file into a dos filesystem
fdt - flattened device tree utility commands
flinfo - print FLASH memory information
fstype - Look up a filesystem type
go - start application at address 'addr'
gpt - GUID Partition Table
help - print command description/usage
icache - enable or disable instruction cache
iminfo - print header information for application image
itest - return true/false on integer compare
load - load binary file from a filesystem
loadb - load binary file over serial line (kermit mode)
loads - load S-Record file over serial line
loadx - load binary file over serial line (xmodem mode)
loady - load binary file over serial line (ymodem mode)
loop - infinite loop on address range
ls - list files in a directory (default /)
md - memory display
mii - MII utility commands
mm - memory modify (auto-incrementing address)
mmc - MMC sub system
mmcinfo - display MMC info
mw - memory write (fill)
nm - memory modify (constant address)
part - disk partition related commands
printenv- print environment variables
protect - enable or disable FLASH write protection
reset - Perform RESET of the CPU
run - run commands in an environment variable
save - save file to a filesystem
saveenv - save environment variables to persistent storage
setenv - set environment variables
setexpr - set environment variable as the result of eval expression
showvar - print local hushshell variables
size - determine a file's size
source - run script from memory
sysboot - command to get and boot from syslinux files
test - minimal test like /bin/sh
thordown- TIZEN "THOR" downloader
true - do nothing, successfully
ums - Use the UMS [User Mass Storage]
version - print monitor, compiler and linker version
LANDROVER #