This is a demo of a universal SD card image, which should be bootable on almost any Allwinner A10/A10s/A20 device. With an installer of u-boot v2015.07 as the initial simple payload. By using a HDMI monitor for output and a USB keyboard or FEL button for input, it offers a menu based user interface. Which allows to select and install a suitable board-specific u-boot build.
The installer uses a minimal soc-independent placeholder bootloader to boot, plus some supplementary files in the '/boot/setup' directory on the first ext2 partition. As soon as the real full-fledged u-boot v2015.07 bootloader takes over, it expects to find the '/boot/boot.scr' file and a linux kernel in the '/boot' directory. After that, the '/boot/setup' directory becomes unnecessary.
This demo SD card image only takes care of the bootloader. The kernel and rootfs are not provided here and need to be additionally included to get a usable linux system. The providers of SD card images with Linux distributions for Allwinner boards may potentially try to use this SD card image as a starting point. Now it is a full-fledged Debian Linux installer. The installation of it requires a working Internet connection.
Usage instructions
- If you have a Banana Pro board, then stop here and don't use this SD card image on it! There is a risk of damaging hardware on this particular board because of the way how USB OTG ID pin is routed in Banana Pro.
- Just write the SD card image to some SD card ("xzcat 20141215-sunxi-bootsetup-prototype-v6.img.xz > /dev/sdX" and then "sync").
- Insert the SD card in your Allwinner device.
- Connect a monitor or TV via a HDMI cable or alternatively get access to the UART serial console.
- Power on the device.
- Follow the instructions on screen.
Revision history
v2: Updated the SD card image to address a simple typo in /boot/setup/boot-a10s.cmd and make it really bootable on A10s.
v3: Updated the SD card image to reduce the failsafe DRAM clock frequency from 360MHz to 312MHz for a safety headroom even on boards with poor DRAM reliability.
v4: The failsafe DRAM clock frequency is back to 360MHz because Cubietruck board can't handle low clock frequencies. But the 'emr1 = 4' change is kept. Also added the Debian installer as another payload to make this demo a little bit more useful.
v5: The Debian installer now runs on the UART serial console instead of HDMI (which is a more reasonable choice, because the current version of Debian can't support HDMI anyway and is only suitable for headless servers). The version of u-boot is upgraded from v2015.01-rc3 to v2015.01 release.
v6: A newer snapshot of the Debian installer (07 Sep 2015), which now has simplefb support and works fine with HDMI monitors. The version of u-boot is also upgraded to v2015.07. Note: this particular snapshot of Debian bundles the kernel, which may fail to reboot after the end of installation: http://lists.infradead.org/pipermail/linux-arm-kernel/2015-August/365911.html (so you will have to reset the board if it gets stuck).
Reconstructing this SD card image by building all of its parts from sources (this is optional)
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Use buildroot from https://github.com/ssvb/buildroot/commits/20141215-sunxi-bootsetup-prototype to build the initramfs file "/boot/setup/rootfs.cpio.uboot":
git clone -b 20141215-sunxi-bootsetup-prototype https://github.com/ssvb/buildroot.git cd buildroot make sunxi_bootsetup_defconfig make -
Use https://github.com/ssvb/linux-sunxi/commits/20141215-sunxi-bootsetup-prototype to build the linux kernel ("/boot/setup/uImage-3.18-bootsetup") and dtb files ("/boot/setup/sun4i-a10-bootsetup.dtb", "/boot/setup/sun5i-a10s-bootsetup.dtb", "/boot/setup/sun7i-a20-bootsetup.dtb"):
git clone -b 20141215-sunxi-bootsetup-prototype https://github.com/ssvb/linux-sunxi.git cd linux-sunxi make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- sunxi_bootsetup_defconfig make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- LOADADDR=0x40008000 -j2 uImage dtbs -
Use upstream u-boot v2015.07 sources to build the u-boot binaries for all the supported Allwinner boards and populate the "/boot/setup/u-boot-binaries" directory.
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Use https://github.com/ssvb/u-boot-sunxi/commits/20141215-sunxi-bootsetup-prototype to build the bootloader for the SD card:
git clone -b 20141215-sunxi-bootsetup-prototype https://github.com/ssvb/u-boot-sunxi.git cd u-boot-sunxi make CROSS_COMPILE=arm-linux-gnueabihf- sunxi-generic-a10-a13-a20_defconfig make CROSS_COMPILE=arm-linux-gnueabihf- -j2 sudo dd if=u-boot-sunxi-with-spl.bin of=/dev/sdX bs=1024 seek=8 sync -
For the details about hooking the standard Debian installer and keeping it up to date, see http://linux-sunxi.org/Mainline_Debian_HowTo#Using_a_ready-made_installation_SD_card_image_instead_of_bootstrapping