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[46.193.119.166]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43b919e7111sm6381199f8f.37.2026.03.26.02.10.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Mar 2026 02:10:49 -0700 (PDT) From: Fidelio Lawson X-Google-Original-From: Fidelio Lawson Date: Thu, 26 Mar 2026 10:10:21 +0100 Subject: [PATCH 1/3] dt-bindings: dsa: microchip: add KSZ low-loss cable errata properties Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260326-ksz87xx_errata_low_loss_connections-v1-1-79a698f43626@exotec.com> References: <20260326-ksz87xx_errata_low_loss_connections-v1-0-79a698f43626@exotec.com> In-Reply-To: <20260326-ksz87xx_errata_low_loss_connections-v1-0-79a698f43626@exotec.com> To: Woojung Huh , UNGLinuxDriver@microchip.com, Andrew Lunn , Vladimir Oltean , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Marek Vasut , Maxime Chevallier Cc: Woojung Huh , netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Fidelio Lawson X-Mailer: b4 0.15.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1774516248; l=2567; i=fidelio.lawson@exotec.com; s=20260326; h=from:subject:message-id; bh=c7lQdgxqQoIzJtukGcni61BhLUSZ/QFFuAEFNiGJ1gU=; b=gj7AGcTZYGRoM7Sy8eZ6g+SR04PncDwMsa3hX82B5caMFrk8jBIIfC/yGLfiXNoWrTzH/QhTl 4xqPPoU+hVDCLFug8cRooDd/V7CsmsZBsmKPrftyKqTH8hY5vJ/yU9q X-Developer-Key: i=fidelio.lawson@exotec.com; a=ed25519; pk=866eH9Bmmpjc+ctgkr5T1uXxBefZzob3tEEuiVWZ6BI= Microchip KSZ87xx switches are affected by the "Module 3: Equalizer fix for short cables" erratum described in DS80000687C. The embedded PHY receivers are tuned for long, high-loss cables, which may cause signal distortion when operated with short or low-loss cabling such as CAT5e or CAT6. In these cases, the PHY may fail to establish a link due to internal over-amplification. Two workarounds are provided by Microchip, each configuring a different indirect register value to adjust the PHY equalizer settings. This patch introduces two new device tree properties to enable and select the appropriate workaround: - microchip,low-loss-errata-enable: boolean enabling the feature - microchip,low-loss-errata: selects workaround 1 or 2 (default: 1) These properties allow board designers to opt into the errata fix according to the targeted cable characteristics of their platform. Signed-off-by: Fidelio Lawson --- .../devicetree/bindings/net/dsa/microchip,ksz.yaml | 18 ++++++++++++++= ++++ 1 file changed, 18 insertions(+) diff --git a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml b= /Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml index 8d4a3a9a33fc..ddfbc36aace6 100644 --- a/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml +++ b/Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml @@ -85,6 +85,24 @@ properties: enum: [2000, 4000, 8000, 12000, 16000, 20000, 24000, 28000] default: 8000 =20 + microchip,low-loss-errata-enable: + description: + The receiver of the embedded PHYs is tuned by default to support lon= g cable length applications. This was developed + using low quality, high loss cables. Because of this, the equalizer = in the PHY may amplify high amplitude receiver signals + to the point that the signal is distorted internally, preventing a l= ink from being established. + A more balanced receiver setting has been found that still functions= at the long cable lengths and also supports + low loss applications. + If present, enables the selected errata workaround. If absent, the + workaround is disabled regardless of microchip,cat56-errata value. + type: boolean + + microchip,low-loss-errata: + description: + Selects Microchip KSZ87xx CAT5e/CAT6 short-cable errata workaround. + 1 =3D Workaround 1, 2 =3D Workaround 2. If omitted, workaround 1 is = applied. + enum: [1, 2] + default: 1 + interrupts: maxItems: 1 =20 --=20 2.53.0