Re: [PATCH v7 8/9] ARM: dts: turris-omnia: Add MCU system-controller node

["Marek Behún" <kabel@kernel.org>]

On Fri, 26 Apr 2024 18:01:20 +0200
Gregory CLEMENT <gregory.clement@bootlin.com> wrote:

> Hello Marek,
> 
> > Turris Omnia's MCU provides various features that can be configured over
> > I2C at address 0x2a. Add device-tree node.
> >
> > Fixes: 26ca8b52d6e1 ("ARM: dts: add support for Turris Omnia")  
> 
> Is it really a fix ?
> 
> It seems that the node you add depends on the firmware support that was
> not yet added.
> 
> Gregory

It is a fix in the sense that Omnia always had the MCU, and so
device-tree without the MCU node was incorrect.

Since device-trees should be (if possible) backwards and forwards
compatible, this should not be a problem.

But I am guessing it might be because of what new U-Boot does: if it
finds the MCU node in the device-tree, it will add a reset gpio property
for ethernet PHY, linking it to the MCU node. So if this
patch got backported to older kernel where the MCU driver is not
present, and the board had this new U-Boot, the kernel would not create
the eth2 interface, because it would be waiting for a driver providing
the GPIO.

So hmm, maybe I should drop the Fixes tag.