[PATCH v2 0/2] arm64: dts: rockchip: fix Ethernet PHY on Theobroma PX30 devices

[PATCH v2 0/2] arm64: dts: rockchip: fix Ethernet PHY on Theobroma PX30 devices

[Quentin Schulz]

This removes the reliance on the bootloader setting up the Ethernet PHY
for the Linux kernel to be able to use Ethernet.

This is due to the HW default of the PHY reset line being active and the
MDIO auto-detection mechanism not controlling a PHY's reset line such
that we need to hardcode the PHY ID in the compatible property for it to
be usable by the kernel, regardless of what the bootloader is doing.

We only ever had one PHY (DP83825) for both devices, so it's fine to
hardcode this way.

As discussed in v1[1][2], even though they suffer from the same
limitation, only the patch for Ringneck is targeted for stable releases.

Ethernet is currently broken if the bootloader is built without Ethernet
support for those two boards. Cobra is a product for which the software
stack can only be replaced or updated by Cherry. Ringneck is a SoM
supported since kernel 6.1, the user is likely going to write their own
bootloader support based on the motherboard they attach the SoM to. They
may disable Ethernet support in the bootloader if they don't need to
(e.g. to reduce the attack surface or have an easier time certifying a
 device when arguing with an audit company).

Ethernet-less bootloader was supported until commit e463625af7f9
("arm64: dts: rockchip: move reset to dedicated eth-phy node on
ringneck") for Ringneck. Because I do not control what our users have
made with Ringneck, and that it used to work before commit e463625af7f9,
the patch fixing the issue on Ringneck is a candidate for backporting to
stable.

Cobra never supported it due to its support in the kernel being added 
with this (unknown at the time) limitation. Moreover, Cherry controls
the whole software stack so this is already patched downstream whenever
required. Therefore, the patch fixing the issue on Cobra is not marked
as a candidate for backporting to stable (but if it ends up being
backported, it's fine as well).

[1] https://lore.kernel.org/linux-rockchip/38452338-6e65-47ad-a696-b90c02ac42f0@lunn.ch/
[2] https://lore.kernel.org/linux-rockchip/b2f12140-ee3d-45bc-864e-d51317c83b8d@cherry.de/

Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
---
Changes in v2:
- removed Cc stable on Cobra's patch,
- Link to v1: https://patch.msgid.link/20260202-px30-eth-phy-v1-0-ef365be64922@cherry.de

---
Quentin Schulz (2):
      arm64: dts: rockchip: fix Ethernet PHY not found on PX30 Cobra
      arm64: dts: rockchip: fix Ethernet PHY not found on PX30 Ringneck

 arch/arm64/boot/dts/rockchip/px30-cobra.dtsi    | 2 +-
 arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
base-commit: c1f49dea2b8f335813d3b348fd39117fb8efb428
change-id: 20260130-px30-eth-phy-676fa181e116

Best regards,
--  
Quentin Schulz <quentin.schulz@cherry.de>

[PATCH v2 1/2] arm64: dts: rockchip: fix Ethernet PHY not found on PX30 Cobra

[Quentin Schulz]

From: Quentin Schulz <quentin.schulz@cherry.de>

When not passing the PHY ID with an ethernet-phy-idX.Y compatible
property, the MDIO bus will attempt to auto-detect the PHY by reading
its registers and then probing the appropriate driver. For this to work,
the PHY needs to be in a working state.

Unfortunately, the net subsystem doesn't control the PHY reset GPIO when
attempting to auto-detect the PHY. This means the PHY needs to be in a
working state when entering the Linux kernel. This historically has been
the case for this device, but only because the bootloader was taking
care of initializing the Ethernet controller even when not using it.
We're attempting to support the removal of the network stack in the
bootloader, which means the Linux kernel will be entered with the PHY
still in reset and now Ethernet doesn't work anymore.

The devices in the field only ever had a TI DP83825, so let's simply
bypass the auto-detection mechanism entirely by passing the appropriate
PHY IDs via the compatible.

Fixes: bb510ddc9d3e ("arm64: dts: rockchip: add px30-cobra base dtsi and board variants")
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
---
 arch/arm64/boot/dts/rockchip/px30-cobra.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/rockchip/px30-cobra.dtsi b/arch/arm64/boot/dts/rockchip/px30-cobra.dtsi
index b7e669d8ba4d1..add917af5de78 100644
--- a/arch/arm64/boot/dts/rockchip/px30-cobra.dtsi
+++ b/arch/arm64/boot/dts/rockchip/px30-cobra.dtsi
@@ -397,7 +397,7 @@ &io_domains {
 
 &mdio {
 	dp83825: ethernet-phy@0 {
-		compatible = "ethernet-phy-ieee802.3-c22";
+		compatible = "ethernet-phy-id2000.a140";
 		reg = <0x0>;
 		pinctrl-names = "default";
 		pinctrl-0 = <&phy_rst>;

-- 
2.53.0

[PATCH v2 2/2] arm64: dts: rockchip: fix Ethernet PHY not found on PX30 Ringneck

[Quentin Schulz]

From: Quentin Schulz <quentin.schulz@cherry.de>

When not passing the PHY ID with an ethernet-phy-idX.Y compatible
property, the MDIO bus will attempt to auto-detect the PHY by reading
its registers and then probing the appropriate driver. For this to work,
the PHY needs to be in a working state.

Unfortunately, the net subsystem doesn't control the PHY reset GPIO when
attempting to auto-detect the PHY. This means the PHY needs to be in a
working state when entering the Linux kernel. This historically has been
the case for this device, but only because the bootloader was taking
care of initializing the Ethernet controller even when not using it.
We're attempting to support the removal of the network stack in the
bootloader, which means the Linux kernel will be entered with the PHY
still in reset and now Ethernet doesn't work anymore.

The devices in the field only ever had a TI DP83825, so let's simply
bypass the auto-detection mechanism entirely by passing the appropriate
PHY IDs via the compatible.

Note that this is only an issue since commit e463625af7f9 ("arm64: dts:
rockchip: move reset to dedicated eth-phy node on ringneck") as before
that commit the reset was done by the MAC controller before starting the
MDIO auto-detection mechanism, via the snps,reset-* properties.

Cc: stable@vger.kernel.org
Fixes: e463625af7f9 ("arm64: dts: rockchip: move reset to dedicated eth-phy node on ringneck")
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
---
 arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi b/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi
index 4203b335a2633..973b4c5880e24 100644
--- a/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi
+++ b/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi
@@ -344,7 +344,7 @@ &io_domains {
 
 &mdio {
 	dp83825: ethernet-phy@0 {
-		compatible = "ethernet-phy-ieee802.3-c22";
+		compatible = "ethernet-phy-id2000.a140";
 		reg = <0x0>;
 		pinctrl-names = "default";
 		pinctrl-0 = <&phy_rst>;

-- 
2.53.0