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[83.233.221.53]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c2ae735737csm218957666b.11.2026.09.26.01.21.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 26 Sep 2026 01:21:39 -0700 (PDT) From: Yongzhao Chen To: Andrew Lunn Cc: netdev@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Florian Fainelli , Vladimir Oltean , Christian Marangi , Heiner Kallweit , Russell King , linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, Ziyang Huang Subject: Re: [RFC PATCH net-next v3 4/5] net: dsa: qca8k: flag QCA8337 internal CPU PHYs for SmartSpeed Date: Sat, 26 Sep 2026 10:21:29 +0200 Message-ID: <20260926082129.1632-1-yongzhao.derek@gmail.com> X-Mailer: git-send-email 2.45.2.windows.1 In-Reply-To: <69b36e16-eece-4739-9208-96bd8e60943f@lunn.ch> References: <20260923215858.1653-1-yongzhao.derek@gmail.com> <20260923215858.1653-5-yongzhao.derek@gmail.com> <09d669ff-7aad-4414-880a-21c2e7bf2cd7@lunn.ch> <20260924234814.1734-1-yongzhao.derek@gmail.com> <20260925210153.8717-1-yongzhao.derek@gmail.com> <69b36e16-eece-4739-9208-96bd8e60943f@lunn.ch> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Andrew, > How are the two ports coupled? > > Are there magnetics? Capacitor coupling? I don't have a schematic and have not inspected the board closely myself. What I have are third-party photos of the Redmi AX5400 board (board marking M74). A teardown with the shields removed: https://www.acwifi.net/19451.html Full board: https://www.acwifi.net/wp-content/uploads/2022/03/DSC_4718.jpg Close-up: https://www.acwifi.net/wp-content/uploads/2022/03/DSC_4725.jpg And a repair forum photo of the same board with the shields on: https://remont-aud.net/forum/103-124057-1 Photo: https://remont-aud.net/_fr/1240/2027121.jpg In the full board photo the QCA8337 is under the small shield at the top left and the IPQ5018 is under the diagonal shield in the middle. They are a few centimetres apart, judging from the photo, and I cannot see magnetics or common-mode chokes between them. Just outside the chamfered corner of the QCA8337 shield, between the two chips, the silkscreen shows eight capacitor positions in pairs, C548 to C555. In the forum photo, parallel traces appear to run from this group towards the IPQ5018 shield. That looks like AC coupling on the four pairs, but from the photos I cannot tell whether they are populated, what their values are, or whether they are capacitors at all rather than 0 ohm links. I also cannot identify any bias or termination parts, so I cannot say whether it matches the arrangement in the Micrel note. The OpenWrt DTS for this board sets qcom,dac-preset-short-cable on the IPQ5018 GE PHY. The qca,ar803x.yaml binding describes it as adjusting amplitude, bias current and error correction for a PHY connected to another PHY over a short distance. There is no equivalent setting on the QCA8337 side. Thanks, Yongzhao Chen