F/xilinx and J/xilinx uses different keyword in /proc/device-tree/compatible

[Po-Hsu Lin]

While testing J/xilinx, I noticed that the keyword we use to grep from /proc/device-tree/compatible has to be changed into kv26 instead of k26 that we used for F/xilinx

J/xilinx:
$ cat /proc/device-tree/compatible
xlnx,zynqmp-sk-kv260-rev1xlnx,zynqmp-sk-kv260-revBxlnx,zynqmp-sk-kv260xlnx,zynqmp

F/xilinx:
$ cat /proc/device-tree/compatible
xlnx,zynqmp-smk-k26-rev1xlnx,zynqmp-smk-k26-revBxlnx,zynqmp-smk-k26-revAxlnx,zynqmp-smk-k26xlnx,zynqmp

From what I can found on the Internet, KV260 is "a vision application development platform for Kria K26 SOMs (system-on-module)". But it's better to let the kernel maintainer (Portia) to answer that if this difference is expected.

Related change for tests:
https://code.launchpad.net/~canonical-kernel-team/+git/autotest-client-tests/+merge/443543

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External link: https://warthogs.atlassian.net/browse/PEL-439

[Masahiro Yamada (myamada)]

"K26" is the name of the SOM (System-on-Module).

"KV260" is the name of the SOM + Base board.

I am guessing the Base board overlay was applied on Jammy, but not on Focal.

I think Jammy is correct.

Better to check U-Boot applied the overlay before booting the kernel.

BTW, I checked the focal kernel tree, but did not find "K26". Where did that device tree come from?

[Portia Stephens (portias)]

The device trees comes directly from the Xilinx kernel (https://github.com/Xilinx/linux-xlnx) . It seems like in the focal kernel the overlay for the KV260 SOM did not set a compatible string so the it fell back to the compatible string defined by the baseboard (zynqmp-smk-k26-revA.dts) . When a device tree for rev B of the board was added the compatible string was added to the rev A device tree as well.

The change was added here:
https://github.com/Xilinx/linux-xlnx/commit/70604467dc949d3b77eabaa1288365cb25b2ec23#diff-f19b970e083cc67c8063c7698b0bb6554d69d43190d355adc20945526eda5831

I agree with Masahiro that Jammy is correct. Since the device trees are not in the kernel build and are provided by Xilinx I don't think this is something we can backport to Focal.