netdev - [PATCH v6 3/4] riscv: dts: starfive: visionfive-v1: Setup ethernet phy

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Message-ID: <20231220211743.2490518-4-cristian.ciocaltea@collabora.com>
Date: Wed, 20 Dec 2023 23:17:41 +0200
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Emil Renner Berthing <kernel@...il.dk>,
	Conor Dooley <conor@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Richard Cochran <richardcochran@...il.com>,
	Andrew Lunn <andrew@...n.ch>,
	Jacob Keller <jacob.e.keller@...el.com>
Cc: linux-riscv@...ts.infradead.org,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	kernel@...labora.com,
	Emil Renner Berthing <emil.renner.berthing@...onical.com>
Subject: [PATCH v6 3/4] riscv: dts: starfive: visionfive-v1: Setup ethernet phy

The StarFive VisionFive V1 SBC uses a Motorcomm YT8521 PHY supporting
RGMII-ID, but requires manual adjustment of the RX internal delay to
work properly.

The default RX delay provided by the driver is 1.95 ns, which proves to
be too high. Applying a 50% reduction seems to mitigate the issue.

Also note this adjustment is not necessary on BeagleV Starlight SBC,
which uses a Microchip PHY.  Hence, there is no indication of a
misbehaviour on the GMAC side, but most likely the issue stems from
the Motorcomm PHY.

While at it, drop the redundant gpio include, which is already provided
by jh7100-common.dtsi.

Co-developed-by: Emil Renner Berthing <emil.renner.berthing@...onical.com>
Signed-off-by: Emil Renner Berthing <emil.renner.berthing@...onical.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>
Reviewed-by: Andrew Lunn <andrew@...n.ch>
---
 .../jh7100-starfive-visionfive-v1.dts         | 22 ++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts b/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
index e82af72f1aaf..692c696e1ab4 100644
--- a/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
+++ b/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
@@ -6,7 +6,6 @@
 
 /dts-v1/;
 #include "jh7100-common.dtsi"
-#include <dt-bindings/gpio/gpio.h>
 
 / {
 	model = "StarFive VisionFive V1";
@@ -18,3 +17,24 @@ gpio-restart {
 		priority = <224>;
 	};
 };
+
+&gmac {
+	phy-handle = <&phy>;
+};
+
+/*
+ * The board uses a Motorcomm YT8521 PHY supporting RGMII-ID, but requires
+ * manual adjustment of the RX internal delay to work properly.  The default
+ * RX delay provided by the driver (1.95ns) is too high, but applying a 50%
+ * reduction seems to mitigate the issue.
+ *
+ * It is worth noting the adjustment is not necessary on BeagleV Starlight SBC,
+ * which uses a Microchip PHY.  Hence, most likely the Motorcomm PHY is the one
+ * responsible for the misbehaviour, not the GMAC.
+ */
+&mdio {
+	phy: ethernet-phy@0 {
+		reg = <0>;
+		rx-internal-delay-ps = <900>;
+	};
+};
-- 
2.43.0