rpi4: How to use armv7 dts on aarch64?

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rpi4: How to use armv7 dts on aarch64?

Postby mmirate » Tue May 18, 2021 6:43 pm

I have some hardware which, on armv7 with the patchy kernel, works with a dts that is compiled and placed in /boot/overlays.

How should I alter the dts, and procedures for compiling/installing the dtb, to get the hardware working on linux-aarch64?
Last edited by mmirate on Wed May 19, 2021 12:00 pm, edited 1 time in total.
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Re: How to use rpi4 armv7 dts on aarch64?

Postby graysky » Tue May 18, 2021 7:00 pm

Not sure how you are providing the custom files. Is there a reason you can't just build them for aarch64 and supply them the same way?
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Re: How to use rpi4 armv7 dts on aarch64?

Postby mmirate » Tue May 18, 2021 11:44 pm

The custom file is a device-tree specification, similar to https://github.com/watterott/RPi-Display/blob/master/software/rpi-display-overlay.dts. On a Raspbian system ... after one finishes puking at Raspbian's kernel patches and Debian-based userland ... one is then supposed to incant "dtc -@ -I dts -O dtb -o rpi-display.dtbo rpi-display.dts", place the resulting file "rpi-display.dtbo" in /boot/overlays, and add a corresponding "dtoverlay=..." line to /boot/config.txt.

On a fresh install of the aarch64 image, even after a "pacman -Syu", that directory does not exist; when I create it, place the file there, modify /boot/config.txt and reboot, the overlay appears to have no effect. And when I try https://archlinuxarm.org/forum/viewtopic.php?f=23&t=14544&sid=763f4a7e57c0ec163e0725962687efe5#p64371, the system fails to boot because u-boot doesn't recognize the "bootz" command.
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Re: rpi4: How to use armv7 dts on aarch64?

Postby mmirate » Sun May 23, 2021 9:57 pm

So apparently "bootz" is inapplicable on arm64 because for (insert reasons here) linux can't do its self-extracting magic-tricks on arm64 like it can on armv7 et al.

Which, so far, knock on wood, narrows my question: given a "bootz" incantation, how do I determine an equivalent "booti" incantation?
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Re: rpi4: How to use armv7 dts on aarch64?

Postby mmirate » Mon May 24, 2021 1:07 am

And, to narrow things even further: how do I make the initramfs image agreeable to "booti"?
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Re: rpi4: How to use armv7 dts on aarch64?

Postby mmirate » Mon May 31, 2021 1:24 am

Okay, so I finally got it to where using u-boot's fdt subsystem would boot the system. I even got a hopeful-looking output from the custom hardware.

But, at the same time, it also somehow booted without i2c support, which caused it to be unable to communicate with the custom battery system, which caused the battery system to powercycle it, and after reapplying power, it hung at the splash screen (i.e. https://elinux.org/R-Pi_Troubleshooting#Coloured_splash_screen), and I don't have another ALARM-based Pi with which to redo the kernel image.

Now what?
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Re: rpi4: How to use armv7 dts on aarch64?

Postby mmirate » Mon May 31, 2021 1:39 pm

Well? Is this a forum or just an echo-chamber!?
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