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From:   Vladimir Oltean <vladimir.oltean@nxp.com>
To:     Hongbo Wang <hongbo.wang@nxp.com>
CC:     Andrew Lunn <andrew@lunn.ch>, Hongjun Chen <hongjun.chen@nxp.com>,
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Subject: Re: [EXT] Re: [PATCH v1] arm64: dts: fsl: ls1028a-rdb: Add dts file
 to choose swp5 as dsa master
Thread-Topic: [EXT] Re: [PATCH v1] arm64: dts: fsl: ls1028a-rdb: Add dts file
 to choose swp5 as dsa master
Thread-Index: AQHXj+75z1qD/BGTVEaJLO5FNXuRQ6txaSUAgAANIYCAAAMJgIAEL8wAgADEv4A=
Date:   Mon, 16 Aug 2021 17:48:03 +0000
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On Mon, Aug 16, 2021 at 06:03:52AM +0000, Hongbo Wang wrote:
> > I was going to suggest as an alternative to define a device tree overla=
y file with
> > the changes in the CPU port assignment, instead of defining a wholly ne=
w 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 fi=
le, so that
> > won't actually work.
>
> hi Vladimir,
>
>   if don't specify "/delete-property/" in this dts file, the correspondin=
g dtb will not work well,
> so I add it to delete 'ethernet' property from mscc_felix_port4 explicitl=
y.

Judging by the reply, I am not actually sure you've understood what has bee=
n 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=3DLSDK-20.12-V5.4

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

/ {
	images {
		/* Base DTB */
		ls1028aqds-dtb {
			description =3D "ls1028aqds-dtb";
			data =3D /incbin/("arch/arm64/boot/dts/freescale/fsl-ls1028a-qds.dtb");
			type =3D "flat_dt";
			arch =3D "arm64";
			os =3D "linux";
			compression =3D "none";
			load =3D <0x90000000>;
			hash@1 {
				algo =3D "crc32";
			};
		};
		/* Overlay */
		fdt@ls1028aqds-13bb {
			description =3D "ls1028aqds-13bb";
			data =3D /incbin/("arch/arm64/boot/dts/freescale/fsl-ls1028a-qds-13bb.dt=
b");
			type =3D "flat_dt";
			arch =3D "arm64";
			load =3D <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.=