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sunxi:[0]全志SoC启动过程分析

sunxi学习:[0]全志SoC启动过程分析

参考:linux-sunxi.org


启动流程:Boot ROM→SPL→U-boot(→Kernel→RootFileSystem)

一、BROM阶段

全志SoC有一个非常具体的启动过程。首先,它执行一个微小的片上 Boot ROM(BROM),然后检查按钮的FEL模式,然后开始检查各种存储选项的有效的引导签名在正确的位置。

上电后,SoC开始从BROM所在的地址0xffff0000获取指令。BROM分为两部分:第一部分(0xffff0000)是FEL模式,第二部分是eGON.BRM(位于0xffff4000)。

FEL:FEL是包含在Allwinner设备上的BootROM中的低级子例程。它用于使用USB的设备的初始编程和恢复。所以,全志平台一般不会砖,就是有这个FEL。

一般来说,BROM首先检查SD卡(SD/MMC)启动可用性,其次再检查Nand Flash是否可以启动,然后再检查SPI Nor Flash的启动可用性,如果都无法启动则进入 FEL 模式。当程序初始化启动介质成功后,就从固定位置读入bootloader的Boot0到SRAM,然后跳到SRAM执行。

将u-boot烧录进SD卡

SD Card Layout:
start size usage
0 8KB Unused, available for partition table etc.
8 24KB Initial SPL loader
32 512KB U-Boot
544 128KB environment
672 352KB reserved
1024 - Free for partitions

根据SD Card Layout表,使用dd将u-boot烧录进SD卡:

sudo dd if=u-boot-sunxi-with-spl.bin of=${card} bs=1024 seek=8
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* * *

## 二、U-boot SPL阶段

SPL(Secondary Program Loader)程序流程如下:
  • 初始化ARM处理器
  • 初始化串口控制台
  • 配置时钟和最基础的分频
  • 初始化SDRAM
  • 配置引脚多路复用功能
  • 启动设备初始化(即上面选择的启动设备)
  • 加载完整的u-boot/kernel程序并转交控制权 使用FEL/USBBoot启动spl
    `sudo ./sunxi-fel uboot u-boot-sunxi-with-spl.bin
        `
    `U-Boot SPL 2017.03-rc2-gc7a25b3-dirty (Mar 11 2017 - 17:09:43)
        DRAM: 256 MiB
        Trying to boot from FEL
        `

    三、U-boot

    由SPL引导进入的U-boot:

    `U-Boot 2017.03-rc2-gc7a25b3-dirty (Mar 11 2017 - 17:09:43 +0800) Allwinner Technology

    CPU: Allwinner H3 (SUN8I 1680) Model: Xunlong Orange Pi Zero DRAM: 256 MiB MMC: SUNXI SD/MMC: 0 MMC: no card present mmc_init: -123, time 1 *** Warning - MMC init failed, using default environment

    In: serial Out: serial Err: serial Net: phy interface0 eth0: ethernet@1c30000 starting USB… USB0: USB EHCI 1.00 USB1: USB OHCI 1.0 scanning bus 0 for devices… 1 USB Device(s) found scanning usb for storage devices… 0 Storage Device(s) found Hit any key to stop autoboot: 0 u-boot@sun8i $ ? ? - 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’ bootefi - Boots an EFI payload from memory bootelf - Boot from an ELF image in memory bootm - boot application image from memory bootp - boot image via network using BOOTP/TFTP protocol 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 dhcp - boot image via network using DHCP/TFTP protocol dm - Driver model low level access echo - echo args to console editenv - edit environment variable env - environment handling commands 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 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 fstype - Look up a filesystem type go - start application at address ‘addr’ gpio - query and control gpio pins help - print command description/usage iminfo - print header information for application image imxtract- extract a part of a multi-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 mdio - MDIO utility commands mii - MII utility commands mm - memory modify (auto-incrementing address) mmc - MMC sub system mmcinfo - display MMC info mw - memory write (fill) nfs - boot image via network using NFS protocol nm - memory modify (constant address) part - disk partition related commands ping - send ICMP ECHO_REQUEST to network host printenv- print environment variables pxe - commands to get and boot from pxe files 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 sleep - delay execution for some time source - run script from memory sysboot - command to get and boot from syslinux files test - minimal test like /bin/sh tftpboot- boot image via network using TFTP protocol true - do nothing, successfully usb - USB sub-system usbboot - boot from USB device version - print monitor, compiler and linker version u-boot@sun8i $