linux-kernel - [PATCH net-next 1/2] dt-bindings: net: dsa: microchip: Add strap description

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Message-Id: <20250910-ksz-strap-pins-v1-1-6308bb2e139e@bootlin.com>
Date: Wed, 10 Sep 2025 16:55:24 +0200
From: Bastien Curutchet <bastien.curutchet@...tlin.com>
To: Woojung Huh <woojung.huh@...rochip.com>, UNGLinuxDriver@...rochip.com, 
 Andrew Lunn <andrew@...n.ch>, Vladimir Oltean <olteanv@...il.com>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Marek Vasut <marex@...x.de>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Miquèl Raynal <miquel.raynal@...tlin.com>, 
 Pascal Eberhard <pascal.eberhard@...com>, 
 Woojung Huh <Woojung.Huh@...rochip.com>, netdev@...r.kernel.org, 
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
 "Bastien Curutchet (Schneider Electric)" <bastien.curutchet@...tlin.com>
Subject: [PATCH net-next 1/2] dt-bindings: net: dsa: microchip: Add strap
 description

At reset, some KSZ switches use strap-based configuration. If the
required pull-ups/pull-downs are missing (by mistake or by design to
save power) the pins may float and the configuration can go wrong.

Add a strap description that can be used by the driver to drive the
strap pins during reset. It consists of a 'reset' pinmux configuration
and a set of strap GPIOs.
Since the pins used and the nature of the configuration differ from one
KSZ switch to another, GPIO names aren't used.

Signed-off-by: Bastien Curutchet (Schneider Electric) <bastien.curutchet@...tlin.com>
---
 Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml b/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
index eb4607460db7f32a4dffd416e44b61c2674f731e..f40a5e3cd0e4d39c809a1fb6697bc3bc64f35fec 100644
--- a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
+++ b/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml
@@ -37,6 +37,13 @@ properties:
       - microchip,ksz8567
       - microchip,lan9646

+  pinctrl-names:
+    items:
+      - const: default
+      - const: reset
+        description:
+          Used during reset for strap configuration.
+
   reset-gpios:
     description:
       Should be a gpio specifier for a reset line.
@@ -80,6 +87,11 @@ properties:
     enum: [2000, 4000, 8000, 12000, 16000, 20000, 24000, 28000]
     default: 8000

+  strap-gpios:
+    description:
+      Strap pins to drive during reset. For KSZ8463, the first GPIO drives the
+      RXDO line, the second one drives the RXD1 line.
+
   interrupts:
     maxItems: 1

-- 
2.51.0