2014-04-29 00:24:04 +04:00
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# Allwinner A10
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* http://linux-sunxi.org
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# Hardware Information
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The A10 is a system-on chip. There are many devices based on it, for example
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the CubieBoard and the Rikomagic mk802 (versions I and II).
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* ARMv7 Architecture (Cortex-A8)
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* Mali 400MP GPU
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* CedarX VPU
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* SD Card Storage
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* 1GB RAM (DDR)
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* 4GB NAND Flash
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* Video Outputs
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* HDMI Video Output
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* Ethernet
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* USB
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# Setting up the Haiku SD card
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Not so fun layout here. The A10 boot ROM reads raw blocks from the SD card
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(MBR style), so the bootloader can't just be dropped in a FAT32 partition.
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* 8KB partition table
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* 24KB SPL loader
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* 512KB u-boot
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* 128KB u-boot environment variables
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* 352KB unused
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* partition 1 -- FAT32 or ext2 (anything u-boot can read is fine)
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* partition 2 -- BeFS, Haiku filesystem, type 'eb'
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Note this layout can be a bit different depending on the u-boot version used,
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some versions will store the environment in uEnv.txt in the FAT32 partition
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instead. Since everything is loaded from the SD Card, we are free to customize
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the u-boot or even remove it and get haiku_loader booting directly.
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## Boot Partition
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### Required Files
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* haiku_loader: Haiku Loader
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* haiku-floppyboot.tgz: Compressed image with Haiku kernel
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# Booting
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1. SOC load SPL
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2. SPL loads u-boot
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2. u-boot loads and run the kernel
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SPL is a small binary (24K) loaded from a fixed location on the SD card. It
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does minimal hardware initializations, then loads u-boot, also from the SD
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card. From there on things go as usual.
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In the long term, we can make haiku_loader be an SPL executable on this
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platform, if it fits the 24K size limit, or have a custom stage1 that loads it.
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For now, u-boot can be an useful debugging tool.
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## Script.bin
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In order to work on different devices (RAM timings, PIO configs, ...), the
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Linux kernels for Allwinner chips use a "script.bin" file. This is loaded to
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RAM at a fixed address by u-boot, then the Kernel parses it and uses it to
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configure the hardware (similar to FDT).
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We should probably NOT use this, and convert the script.bin file to an FDT
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instead. The format is known and there are tools to convert the binary file
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to an editable text version and back (bin2fex and fex2bin).
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This FEX stuff isn't merged in mainline Linux, and lives on as Allwinner
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patches. The mainline Linux kernel has some A10 support, rewritten to use
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FDT. We may use the FDT files from there for the most common boards.
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# Emulation support
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qemu 1.0 has a Cubieoard target which emulates this chip.
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2014-04-29 23:45:23 +04:00
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# Useful links
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Arch Linux instructions on creating a bootable SD card (partition layout, etc)
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http://archlinuxarm.org/platforms/armv7/allwinner/cubieboard#qt-platform_tabs-ui-tabs2
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Linux SunXi: mainline Linux support for the Allwinner chips. Lots of docs on the hardware.
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http://linux-sunxi.org/
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