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a868598a48
Since we lack information about the DRAM initialization for the Allwinner A64 SoC, booting any A64 based board like the Pine64 is a bit involved at the moment. Add a README file to explain the process. Signed-off-by: Andre Przywara <andre.przywara@arm.com> Reviewed-by: Tom Rini <trini@konsulko.com> [trini: Move to board/sunxi/ from doc/] Signed-off-by: Tom Rini <trini@konsulko.com>
99 lines
4.6 KiB
Plaintext
99 lines
4.6 KiB
Plaintext
Pine64 board README
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====================
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The Pine64(+) is a single board computer equipped with an AArch64 capable ARMv8
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compliant Allwinner A64 SoC.
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This chip has ARM Cortex A-53 cores and thus can run both in AArch32
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(compatible to 32-bit ARMv7) and AArch64 modes. Upon reset the SoC starts
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in AArch32 mode and executes 32-bit code from the Boot ROM (BROM).
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This has some implications on U-Boot.
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Quick start
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============
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- Get hold of a boot0.img file (see below for more details).
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- Get the boot0img tool source from the tools directory in [1] and compile
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that on your host.
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- Build U-Boot:
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$ export CROSS_COMPILE=aarch64-linux-gnu-
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$ make pine64_plus_defconfig
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$ make
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- You also need a compiled ARM Trusted Firmware (ATF) binary. Checkout the
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"allwinner" branch from the github repository [2] and build it:
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$ export CROSS_COMPILE=aarch64-linux-gnu-
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$ make PLAT=sun50iw1p1 DEBUG=1 bl31
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The resulting binary is build/sun50iw1p1/debug/bl31.bin.
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Now put an empty (or disposable) micro SD card in your card reader and learn
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its device file name, replacing /dev/sd<x> below with the result (that could
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be /dev/mmcblk<x> as well):
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$ ./boot0img --device /dev/sd<x> -e -u u-boot.bin -B boot0.img \
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-d trampoline64:0x44000 -s bl31.bin -a 0x44008 -p 100
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(either copying the respective files to the working directory or specifying
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the paths directly)
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This will create a new partition table (with a 100 MB FAT boot partition),
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copies boot0.img, ATF and U-Boot to the proper locations on the SD card and
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will fill in the magic Allwinner header to be recognized by boot0.
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Prefix the above call with "sudo" if you don't have write access to the
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uSD card. You can also use "-o output.img" instead of "--device /dev/sd<x>"
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to create an image file and "dd" that to the uSD card.
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Omitting the "-p" option will skip the partition table.
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Now put this uSD card in the board and power it on. You should be greeted by
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the U-Boot prompt.
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Main U-Boot
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============
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The main U-Boot proper is a real 64-bit ARMv8 port and runs entirely in the
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64-bit AArch64 mode. It can load any AArch64 code, EFI applications or arm64
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Linux kernel images (often named "Image") using the booti command.
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Launching 32-bit code and kernels is technically possible, though not without
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drawbacks (or hacks to avoid them) and currently not implemented.
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SPL support
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============
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The main task of the SPL support is to bring up the DRAM controller and make
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DRAM actually accessible. At the moment there is no documentation or source
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code available which would do this.
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There are currently two ways to overcome this situation: using a tainted 32-bit
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SPL (involving some hacks and resulting in a non-redistributable binary, thus
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not described here) or using the Allwinner boot0 blob.
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boot0 method
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-------------
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boot0 is Allwiner's secondary program loader and it can be used as some kind
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of SPL replacement to get U-Boot up and running.
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The binary is a 32 KByte blob and contained on every Pine64 image distributed
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so far. It can be easily extracted from a micro SD card or an image file:
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# dd if=/dev/sd<x> of=boot0.bin bs=8k skip=1 count=4
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where /dev/sd<x> is the device name of the uSD card or the name of the image
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file. Apparently Allwinner allows re-distribution of this proprietary code
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as-is.
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For the time being this boot0 blob is the only redistributable way of making
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U-Boot work on the Pine64. Beside loading the various parts of the (original)
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firmware it also switches the core into AArch64 mode.
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The original boot0 code looks for U-Boot at a certain place on an uSD card
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(at 19096 KB), also it expects a header with magic bytes and a checksum.
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There is a tool called boot0img[1] which takes a boot0.bin image and a compiled
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U-Boot binary (plus other binaries) and will populate that header accordingly.
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To make space for the magic header, the pine64_plus_defconfig will make sure
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there is sufficient space at the beginning of the U-Boot binary.
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boot0img will also take care of putting the different binaries at the right
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places on the uSD card and works around unused, but mandatory parts by using
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trampoline code. See the output of "boot0img -h" for more information.
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boot0img can also patch boot0 to avoid loading U-Boot from 19MB, instead
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fetching it from just behind the boot0 binary (-B option).
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FEL boot
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=========
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FEL is the name of the Allwinner defined USB boot protocol built-in the
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mask ROM of most Allwinner SoCs. It allows to bootstrap a board solely
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by using the USB-OTG interface and a host port on another computer.
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Since FEL boot does not work with boot0, it requires the libdram hack, which
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is not described here.
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[1] https://github.com/apritzel/pine64/
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[2] https://github.com/apritzel/arm-trusted-firmware.git
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