[PATCH net-next v4 1/2] dt-bindings: net: ethernet-phy: add needs-host-firmware

[Aleksei Sviridkin <f@lex.la>]

A PHY can be one that the host has to load firmware into before it can
be driven at all. A controller that connects to such a PHY at setup,
before its driver has loaded, gets the generic driver or no PHY at all,
and one that connects only once gets no working PHY on that port for the
rest of the uptime, even though the PHY works seconds later.

The flag declares that. A consumer that sees it keeps the port and
connects the PHY once its driver binds. It describes the PHY, so it
sits on the PHY node and needs no prefix naming one.

firmware-name is not used for this: it names the file to load, and the
EN8811H driver keeps its two blob names in code, so it would only be
read as a presence flag.

The need is not derived from the compatible because the knowledge that
an ID needs host firmware lives in the PHY driver, and that driver is a
module not yet loaded when the MAC connects, so it has to come from the
device tree.

Found on a Keenetic KN-1012, where the EN8811H behind lan4 has its
driver on the root filesystem and the switch sets its ports up before
that is mounted, so lan4 stayed dead for the uptime.

Assisted-by: LLM
Signed-off-by: Aleksei Sviridkin <f@lex.la>
---
 Documentation/devicetree/bindings/net/ethernet-phy.yaml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/ethernet-phy.yaml b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
index c3ebb3af8b52..73827662ddce 100644
--- a/Documentation/devicetree/bindings/net/ethernet-phy.yaml
+++ b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
@@ -215,6 +215,12 @@ properties:
       used. The absence of this property indicates the muxers
       should be configured so that the external PHY is used.
 
+  needs-host-firmware:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      This PHY runs firmware that the host must load before it can be
+      driven, and is not usable until then.
+
   resets:
     maxItems: 1
 
-- 
2.53.0