65 lines
2.1 KiB
Markdown
65 lines
2.1 KiB
Markdown
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# coreboot-builder
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This is what I use to build my coreboot images. It is heavily based on the
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scripts and configurations used by [skulls](https://github.com/merge/skulls).
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But simplified to support only my very specific hardware and preferences. This
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makes it leaner to use and easier for me to understand it, so it's easier to
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customize (for example, if I want to change the boot order).
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Currently I have only one config for my Thinkpad X230; `capibara`, and I use a
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the "free" config (with the VGA BIOS SeaVGABIOS instead of the Intel one).
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## Build process
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I use a Makefile to orchestrate cloning the coreboot code, checking out the
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right commit, compiling the image, flashing it, etc.
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The coreboot SDK is run from a docker image because I couldn't manage to
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compile everything otherwise.
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## Splash screen
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For an X230 the splash screen image needs to be a JPEG using:
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* with "progressive" turned off
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* "4:2:0 (chroma quartered)" Subsampling
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* 1024px wide and 768px tall
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But the X230 screen happens to be 16:9 (1366px wide, 768px tall). When the
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SaBIOSVABIOS is used, the image is just shown centered in the screen, with
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black blocks on each side. When the Intel VGA is used, the image is stretched
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to fill the whole 1366 x 768 screen. So make sure to plan accordingly to make
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the image look right.
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Also, the SeaBIOS VGA seems to show weird colors when booting. I don't know
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how to fix that, so I just keep the image pure black and white to make it look
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decent.
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## Updates
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I try to follow skull's releases and update the coreboot commit, sdk version
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and config as they do it.
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Last release happened on 2022/05/03.
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## Flashing
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Before flashing, the system needs to boot with the kernel parameter
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`iomem=relaxed`.
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* Reboot the computer
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* When the GRUB screen appears, press `e` to edit the startup command
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* Append `iomem=relaxed` to the kernel command
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* Press `ctrl-x` or `F2` to boot the system with the modification
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* Then flash the new image with:
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```sh
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flash: build/coreboot_top_prepared_12mb.rom layout.txt
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flashrom \
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--force \
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--noverify-all\
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-p internal \
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--layout layout.txt \
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--image bios \
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-w build/coreboot_top_prepared_12mb.rom
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```
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