39 lines
1.6 KiB
Markdown
39 lines
1.6 KiB
Markdown
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U-Boot as a payload to OpenSBI
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==============================
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[U-Boot](https://www.denx.de/wiki/U-Boot) is an open-source primary boot loader.
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It can be used as first and/or second stage boot loader in an embedded
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environment. In the context of OpenSBI, U-boot can be specified as a payload to
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OpenSBI firmware, becoming the boot stage following OpenSBI firmware
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execution.
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The current stable upstream code of U-boot does not yet include all patches
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necessary to fully support OpenSBI. To use U-Boot as an OpenSBI payload, the
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following out-of-tree patch series must be applied to the upstream U-Boot source
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code.
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HiFive Unleashed support for U-Boot
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https://lists.denx.de/pipermail/u-boot/2019-February/358058.html
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This patch series enables a single CPU to execute U-Boot. As a result, the next
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stage boot code such as Linux kernel can also only execute a single CPU. U-Boot
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SMP support for RISC-V can be enabled with the following additional patches.
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https://lists.denx.de/pipermail/u-boot/2019-February/358393.html
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Building and Generating U-Boot images
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=====================================
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Please refer to U-Boot build documentation for detailed instructions on how to build U-Boot images.
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Once U-Boot images are built, Linux kernel image need to be converted to a format
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that U-Boot understands.
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```
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<uboot-dir>/tools/mkimage -A riscv -O linux -T kernel -C none -a 0x80200000 -e 0x80200000 -n Linux -d \
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<linux_build_directory>arch/riscv/boot/Image \
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<linux_build_directory>/arch/riscv/boot/uImage
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```
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Copy the uImage to your tftpboot server path if network boot is required.
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