Re: [PATCH 00/12] arm: xea: Provide support for different XEA board HW versions

[Lukasz Majewski <lukma@denx.de>]

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Hi Fabio,

> Hi Lukasz,
> 
> On Mon, Mar 25, 2024 at 5:48 AM Lukasz Majewski <lukma@denx.de> wrote:
> 
> > The case here is that I'm modifying the *-u-boot.dts{i} files only.
> > In  
> 
> The diff below shows that you are creating imx28-xea-1.dts and
> imx28-xea-2.dts for U-Boot consumption and renaming the upstream
> imx28-xea.dts to imx28-xea.dts.
> 
> create mode 100644 arch/arm/dts/imx28-xea-1.dts
> create mode 100644 arch/arm/dts/imx28-xea-2-u-boot.dtsi
> create mode 100644 arch/arm/dts/imx28-xea-2.dts
> rename arch/arm/dts/{imx28-xea.dts => imx28-xea.dtsi} (100%)
> 
> > other words, u-boot will not support features described in Linux
> > DTS.  
> 
> That's OK and this happens frequently.
> 
> For example, upstream devicetree may describes audio codec,
> but U-Boot does not support audio playback.
> 
> Devicetree should be OS agnostic.
> 
> In U-Boot, we want to re-use the upstream Linux devicetree files
> 'as-is'.
> 
> Adding -u-boot.dtsi files is OK though.
> 
> Can you convert the imx28-xea board to OF_UPSTREAM available in the
> U-Boot next branch?
> 
> > Hence, the rename of files (which would be in sync with Linux at
> > some point) looks like not related to Linux DTS (as even after
> > re-sync with upstream Linux those changes will not be in Linux
> > DTS).  
> 
> I did not understand this part, do you mean that Linux will also do
> the imx28-xea.dts => imx28-xea.dtsi rename and will also have the new
> imx28-xea-1.dts and imx28-xea-2.dts?
> 

Just a small update - the Linux kernel's imx28-xea.dts [1] doesn't have
switch/phy properties as the earlier attempts to add L2 switch support
for Linux mainline were not accepted by the network stack community.

Hence, the decision to omit those properties (and there is no decision
if another attempt for L2 switch support upstreaming will be done in the
near future).

In u-boot the -u-boot.dts[i] files were used to add functionality not
(yet) supported in Linux kernel.

To sum up - I cannot create imx28-xea-1.dts and imx28-xea-2.dts in Linux
as properties which are different in those two revisions are not present
in the current Linux dts description. I cannot say when all XEA
functionality will be added to Linux.

Links:

[1] -
https://elixir.bootlin.com/linux/v6.9-rc1/source/arch/arm/boot/dts/nxp/mxs/imx28-xea.dts

> Regards,
> 
> Fabio Estevam




Best regards,

Lukasz Majewski

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