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S5PV210啟動流程介紹一

手冊上關于iROM/iRAM及Bootloader描述如下：

·The iROM code is placed in internal 64KB ROM. It initializes basic system functions such as clock, stack, and heap.

·The iROM loads the first boot loader image from a specific booting device to internal 96KB SRAM. The booting device is selected by Operating Mode (OM) pins. According to the secure boot key values, the iROM code may do an integrity check on the first boot loader image.

·The first boot loader loads the second boot loader then may check the integrity of the second boot loader according the secure boot key values.

·The second boot loader initializes system clock, UART, and DRAM controller. After initializing DRAM controller, it loads OS image from the booting device to DRAM. According to the secure boot key values, the second boot loader can do an integrity check on the OS image.

·After the booting completes, the second boot loader jumps to the operating system.

按照芯片手冊上的啟動分析圖及上面的描述，總結啟動流程為：

S5PV210上電將iROM(interal ROM)處執行固化的啟動代碼，它對系統時鐘進行初始化，對啟動設備進行判斷，并從啟動設備中復制BL1(大16KB)到iRAM(0xd002_0000處，其中0xd002_0010之前的16個字節存儲的的有BL1的校驗信息和BL1尺寸)中，并對BL1進行校驗，檢驗OK轉入BL1進行執行；BL1執行完成后，開始執行BL2，BL2加載內核，把OS在SDRAM中運行起來。

BL0,BL1,BL2:

(1)BL0：是指S5PV210的iROM中固化的啟動代碼
        作用：初始化系統時鐘，設置看門狗，初始化堆和棧，加載BL1

(2)BL1：是批在iRAM自動從外擴存儲器(nand/sd/usb)中拷貝的uboot.bin二進制文件的頭大16K代碼
        作用：初始化RAM,關閉Cache，設置棧，加載BL2

(3)BL2：是指在代碼重定向后在內存中執行的uboot的完整代碼
        作用：初始化其它外設，加載OS內核

(4)三者之間的關系：(Interal ROM固化代碼)BL0將BL1(bootloader的前16KB--BL1)加載到iRAM；BL1然后在iRAM中運行將BL2(剩下的bootloader)加載到SDRAM；BL2加載內核，把OS在SDRAM中運行起來，終OS是運行在SDRAM(內存)中的。