Re: [PATCH 2/2] arm64: dts: renesas: Drop ethernet-phy-ieee802.3-c22 from PHY compatible string on all RZ boards

["Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>]

On 2024-07-05 23:49:56 +0200, Marek Vasut wrote:
> On 7/3/24 11:36 AM, Niklas Söderlund wrote:
> > On 2024-07-03 10:24:26 +0200, Geert Uytterhoeven wrote:
> > > Niklas: commit 54bf0c27380b95a2 ("arm64: dts: renesas: r8a779g0: Use
> > > MDIO node for all AVB devices") did keep the reset-gpios property in
> > > the PHY node. I guess it should be moved one level up?
> > 
> > It's possible to have a rest-gpios property both in the mdio node and
> > the phy node. The former resets the whole bus while the later a single
> > PHY, at least that's my understanding.
> 
> My understanding of reset GPIO in the MDIO node is that it is used in case
> there might be multiple PHYs with shared reset GPIO on the same MDIO bus.
> Like on the NXP iMX28 .

There is a use-case for a single PHY on the MDIO bus too, at least in 
Linux as I understand it. If the boot process leave the PHY in a bad 
state which prevents it from being probed. A GPIO reset in the MDIO node 
is used when the MDIO bus is registered thus resetting all (in this 
use-case the one) PHYs which later allows them to be probed. A GPIO 
reset on the PHY node is only used after a PHY have been probed, at 
least that is my understanding.

This is the use-case for adding a MDIO node to the AVB driver and 
WhiteHawk.

-- 
Kind Regards,
Niklas Söderlund