linux-kernel - [PATCH net-next v6 08/12] dt-bindings: net: dsa: lantiq,gswip: add support for MII delay properties

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Message-ID: <3c8dc0bab72de05ce5b5a7960b6596009287fa8e.1761938079.git.daniel@makrotopia.org>
Date: Fri, 31 Oct 2025 19:22:09 +0000
From: Daniel Golle <daniel@...rotopia.org>
To: Hauke Mehrtens <hauke@...ke-m.de>, 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>, Simon Horman <horms@...nel.org>,
	Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Andreas Schirm <andreas.schirm@...mens.com>,
	Lukas Stockmann <lukas.stockmann@...mens.com>,
	Alexander Sverdlin <alexander.sverdlin@...mens.com>,
	Peter Christen <peter.christen@...mens.com>,
	Avinash Jayaraman <ajayaraman@...linear.com>,
	Bing tao Xu <bxu@...linear.com>, Liang Xu <lxu@...linear.com>,
	Juraj Povazanec <jpovazanec@...linear.com>,
	"Fanni (Fang-Yi) Chan" <fchan@...linear.com>,
	"Benny (Ying-Tsan) Weng" <yweng@...linear.com>,
	"Livia M. Rosu" <lrosu@...linear.com>,
	John Crispin <john@...ozen.org>
Subject: [PATCH net-next v6 08/12] dt-bindings: net: dsa: lantiq,gswip: add
 support for MII delay properties

Add support for standard tx-internal-delay-ps and rx-internal-delay-ps
properties on port nodes to allow fine-tuning of RGMII clock delays.

The GSWIP switch hardware supports delay values in 500 picosecond
increments from 0 to 3500 picoseconds, with a post-reset default of 2000
picoseconds for both TX and RX delays. The driver currently sets the
delay to 0 in case the PHY is setup to carry out the delay by the
corresponding interface modes ("rgmii-id", "rgmii-rxid", "rgmii-txid").

This corresponds to the driver changes that allow adjusting MII delays
using Device Tree properties instead of relying solely on the PHY
interface mode.

Signed-off-by: Daniel Golle <daniel@...rotopia.org>
---
v6:
 * switch order of patches

v4:
 * remove misleading defaults

v3:
 * redefine ports node so properties are defined actually apply
 * RGMII port with 2ps delay is 'rgmii-id' mode

 .../bindings/net/dsa/lantiq,gswip.yaml         | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/net/dsa/lantiq,gswip.yaml b/Documentation/devicetree/bindings/net/dsa/lantiq,gswip.yaml
index b494f414a3e1..cf01b07f7f44 100644
--- a/Documentation/devicetree/bindings/net/dsa/lantiq,gswip.yaml
+++ b/Documentation/devicetree/bindings/net/dsa/lantiq,gswip.yaml
@@ -22,6 +22,20 @@ patternProperties:
             description:
               Configure the RMII reference clock to be a clock output
               rather than an input. Only applicable for RMII mode.
+          tx-internal-delay-ps:
+            enum: [0, 500, 1000, 1500, 2000, 2500, 3000, 3500]
+            description:
+              RGMII TX Clock Delay defined in pico seconds.
+              The delay lines adjust the MII clock vs. data timing.
+              If this property is not present the delay is determined by
+              the interface mode.
+          rx-internal-delay-ps:
+            enum: [0, 500, 1000, 1500, 2000, 2500, 3000, 3500]
+            description:
+              RGMII RX Clock Delay defined in pico seconds.
+              The delay lines adjust the MII clock vs. data timing.
+              If this property is not present the delay is determined by
+              the interface mode.
 
 maintainers:
   - Hauke Mehrtens <hauke@...ke-m.de>
@@ -127,8 +141,10 @@ examples:
                     port@0 {
                             reg = <0>;
                             label = "lan3";
-                            phy-mode = "rgmii";
+                            phy-mode = "rgmii-id";
                             phy-handle = <&phy0>;
+                            tx-internal-delay-ps = <2000>;
+                            rx-internal-delay-ps = <2000>;
                     };
 
                     port@1 {
-- 
2.51.2