sunxi学习： [0]全杂志SoC启动过程分析参考： linux-sunxi.org
启动过程： bootromsplu-boot (kernelroot file system ) )。
一、BROM阶段的有志SoC有非常具体的启动流程。 首先，运行小片上的bootrom(brom )，然后检查按钮的FEL模式，再开始检查各种存储选项的有效引导签名是否在正确的位置。
接通电源后，SoC从BROM的某个地址0xffff0000开始获取命令。 BROM分为两个部分。 第一部分(0xffff0000 )为FEL模式，第二部分位于eGON.BRM )0xffff4000中。
FEL:FEL是Allwinner设备的BootROM中包含的子例程。 用于使用USB的设备的初始编程和恢复。 所以，全志平台一般做不到砖，就是因为有这个FEL。
一般来说，BROM首先检查SD卡(SD/MMC )的启动可用性，然后检查Nand Flash是否能够启动，然后检查SPI Nor Flash的启动可用性，如果都不能启动，则进入FEL模式。 程序启动介质初始化成功后，从bootloader的Boot0固定位置读取到SRAM，跳转到SRAM执行。
将u-boot写入SD卡SD Card Layout :
startsizeusage08KBUnused，availableforpartitiontableetc.824 kbinitialsplloader 32512 kbu-boot 544128 kb environment 672352 kb reseset
sudoddif=u-boot-sunxi-with-spl.binof=$ { card } bs=1024 seek=8吉，U-boot SPL阶段spl(secondaryprogramloader )
初始化ARM处理器初始化串行控制台配置时钟和基本分频初始化SDRAM配置引脚复用功能引导设备初始化(上面选择的引导设备) )加载完整的u-boot/kernel程序，并使用传递控制权的FEL/USBBoot
sudo./sunxi-felubootu-boot-sunxi-with-spl.binu-boots pl 2017.03-RC2-GC 7a 25 B3-dirty (mar 112017-173360000000-17 )
u-boot 2017.03-RC2-GC 7a 25 b3- dirty (mar 112017-173360093360430800 ) allwinnertechnologycpu 3360 allwinnerh3) sun8i 16660 mi bmmc : sunx isd/MMC : MMC : nocardpresentmmc _ init :-123，time 1*** Warning - MMC init failed， usingdefaultenvironmentin : serial out : serial err : serial net : phy interface0eth 0:以太网@ 1c 30000 starting USB . canning bus0for devices .1USB device (s ) foundscanningusbforstoragedevices .0storage device (s ) foundscanningusbforstoragestorages - alias for ' help ' base-printorsetaddressoffsetbdinfo-printboardinfostructureboot-boot default，i.e .run ' bootcmd run ' bootcmd ' bootefi-bootsanefipayloadfrommemorybootelf-bootfromanelfimageinmemorybootm-bootapplicationimagefrommmememorom/tftpprotocolbootvx-bootvxworksfromanelfimagebootz-bootlinuxzimageimagefrommemorycmp-memory
compareconinfo - print console devices and informationcp - memory copycrc32 - checksum calculationdhcp - boot image via network using DHCP/TFTP protocoldm - Driver model low level accessecho - echo args to consoleeditenv - edit environment variableenv - environment handling commandsexit - exit scriptext2load- load binary file from a Ext2 filesystemext2ls - list files in a directory (default /)ext4load- load binary file from a Ext4 filesystemext4ls - list files in a directory (default /)ext4size- determine a file's sizefalse - do nothing, unsuccessfullyfatinfo - print information about filesystemfatload - load binary file from a dos filesystemfatls - list files in a directory (default /)fatsize - determine a file's sizefatwrite- write file into a dos filesystemfdt - flattened device tree utility commandsfstype - Look up a filesystem typego - start application at address 'addr'gpio - query and control gpio pinshelp - print command description/usageiminfo - print header information for application imageimxtract- extract a part of a multi-imageitest - return true/false on integer compareload - load binary file from a filesystemloadb - load binary file over serial line (kermit mode)loads - load S-Record file over serial lineloadx - load binary file over serial line (xmodem mode)loady - load binary file over serial line (ymodem mode)loop - infinite loop on address rangels - list files in a directory (default /)md - memory displaymdio - MDIO utility commandsmii - MII utility commandsmm - memory modify (auto-incrementing address)mmc - MMC sub systemmmcinfo - display MMC infomw - memory write (fill)nfs - boot image via network using NFS protocolnm - memory modify (constant address)part - disk partition related commandsping - send ICMP ECHO_REQUEST to network hostprintenv- print environment variablespxe - commands to get and boot from pxe filesreset - Perform RESET of the CPUrun - run commands in an environment variablesave - save file to a filesystemsaveenv - save environment variables to persistent storagesetenv - set environment variablessetexpr - set environment variable as the result of eval expressionshowvar - print local hushshell variablessize - determine a file's sizesleep - delay execution for some timesource - run script from memorysysboot - command to get and boot from syslinux filestest - minimal test like /bin/shtftpboot- boot image via network using TFTP protocoltrue - do nothing, successfullyusb - USB sub-systemusbboot - boot from USB deviceversion - print monitor, compiler and linker versionu-boot@sun8i $ 我的个人主页：http://www.techping.cn/我的个人站点博客：http://www.techping.cn/blog/wordpress/我的CSDN博客：http://blog.csdn.net/techping我的简书：http://www.jianshu.com/users/b2a36e431d5e/timeline我的GitHub：https://github.com/techping欢迎相互follow～