RE: [EXT] Re: [PATCH v1] arm64: dts: fsl: ls1028a-rdb: Add dts file to choose swp5 as dsa master

On Mon, Aug 16, 2021 at 06:03:52AM +0000, Hongbo Wang wrote:

quoted

quoted

I was going to suggest as an alternative to define a device tree
overlay file with the changes in the CPU port assignment, instead of
defining a wholly new DTS for the LS1028A reference design board.
But I am pretty sure that it is not possible to specify a
/delete-property/ inside a device tree overlay file, so that won't actually

work.

quoted

hi Vladimir,

  if don't specify "/delete-property/" in this dts file, the
corresponding dtb will not work well, so I add it to delete 'ethernet' property

from mscc_felix_port4 explicitly.

Judging by the reply, I am not actually sure you've understood what has been
said.

I said:

There is an option to create a device tree overlay:

https://www.kernel.org/doc/html/latest/devicetree/overlay-notes.html

We use these for the riser cards on the LS1028A-QDS boards.

https://source.codeaurora.org/external/qoriq/qoriq-components/linux/tree/ar
ch/arm64/boot/dts/freescale/fsl-ls1028a-qds-13bb.dts?h=LSDK-20.12-V5.4

They are included as usual in a U-Boot ITB file:

/ {
	images {
		/* Base DTB */
		ls1028aqds-dtb {
			description = "ls1028aqds-dtb";
			data =
/incbin/("arch/arm64/boot/dts/freescale/fsl-ls1028a-qds.dtb");
			type = "flat_dt";
			arch = "arm64";
			os = "linux";
			compression = "none";
			load = <0x90000000>;
			hash@1 {
				algo = "crc32";
			};
		};
		/* Overlay */
		fdt@ls1028aqds-13bb {
			description = "ls1028aqds-13bb";
			data =
/incbin/("arch/arm64/boot/dts/freescale/fsl-ls1028a-qds-13bb.dtb");
			type = "flat_dt";
			arch = "arm64";
			load = <0x90010000>;
		};
	};
};

In U-Boot, you apply the overlay as following:

tftp $kernel_addr_r boot.itb && bootm
$kernel_addr_r#ls1028aqds#ls1028aqds-13bb

It would have been nice to have a similar device tree overlay that changes the
DSA master from eno2 to eno3, and for that overlay to be able to be applied
(or not) from U-Boot.

But it's _not_ possible, because you cannot put the /delete-property/ (that you
need to have) in the .dtbo file. Or if you put it, it will not delete the property
from the base dtb.

That's all I said.

thanks for the detailed explanation,
I have got your point.

thanks,
hongbo