2021-08-24 17:45:36 +02:00
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Allwinner A10 hardware notes
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############################
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- http://linux-sunxi.org
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Hardware Information
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====================
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The A10 is a system-on chip. There are many devices based on it, for
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example 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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============================
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Not so fun layout here. The A10 boot ROM reads raw blocks from the SD
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card (MBR style), so the bootloader can’t just be dropped in a FAT32
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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
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used, some versions will store the environment in uEnv.txt in the FAT32
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partition instead. Since everything is loaded from the SD Card, we are
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free to customize the u-boot or even remove it and get haiku_loader
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booting directly.
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Boot Partition
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--------------
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Required Files
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~~~~~~~~~~~~~~
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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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=======
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1. SOC load SPL
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2. SPL loads u-boot
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3. 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.
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It does minimal hardware initializations, then loads u-boot, also from
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the SD 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
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loads it. For now, u-boot can be an useful debugging tool.
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Script.bin
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----------
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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
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loaded to RAM at a fixed address by u-boot, then the Kernel parses it
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and uses it to configure the hardware (similar to FDT).
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We should probably NOT use this, and convert the script.bin file to an
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FDT instead. The format is known and there are tools to convert the
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binary file 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
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use FDT. We may use the FDT files from there for the most common boards.
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Emulation support
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=================
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qemu 1.0 has a Cubieoard target which emulates this chip.
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Useful links
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============
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Arch Linux instructions on creating a bootable SD card (partition
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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
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2022-03-14 21:41:23 +01:00
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docs on the hardware. https://linux-sunxi.org/
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