From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [78.32.30.218]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E3BA727470; Fri, 23 Jan 2026 21:32:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=78.32.30.218 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769203958; cv=none; b=Qd/yOOrCZpvVZDFFFGYGjwnZA2gVvXV4shyb7fyS+EXKc9az1sxeczYhGz7YSokjNByYPTVCBrh98ZCQ9+PPOQZm1AtvMObDpQ2b2vMUynxK0UzlTeRK5Dqr6od4/qJDMPBXP/u1TJPA/wnCHziLRAnC58I47YINLbP/BJg/VQU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769203958; c=relaxed/simple; bh=32WWXeXvRXXXnj/kZlQKkKu4K9vlUwiDPTb+2euqXV0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=piyHC64LsUdUJUOOPj7WOCkaK8kTs9SWBtFxNHqAd/cga2Wj0pkiBEQXUqY1gzVZr7ftEtgVGsaxDqb6Gii0GmHcChcuwE3IGrJhECHxCeG+l/z0w2CoaoQ/PHH0YOM5KGOC4jUuQfcLpix+uUG7QuLW+KCdfdgDkMsr61XWYoY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk; spf=none smtp.mailfrom=armlinux.org.uk; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b=UUVNlVPj; arc=none smtp.client-ip=78.32.30.218 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="UUVNlVPj" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=UId/Vzt9Vm2GMBalR/x7lGAofZBiET9NUSj2/ZXMbKw=; b=UUVNlVPj9g+71IhAhxMULD9ivp frh5NGpDhavuR+455fTIxq4AsTEpiUZgXVk0HasxdIi98K7k3RRP7N+iWhDyCxEh9lh11T4f9Ad/6 PkHZeihli1kFmfs5qwHKvpHOI07TrNEtvK+ZiVmZWYLgSWU/ozx5M72kIR/jNtfHAXwDslutBShFe pDtmZQhMAitq6rtrK1c/pSRmDQKWohJzJiPduRvw6pp65OnOtiwP0qXgUQI70/XxvYTr+/9xdihQz SCxnjkqNlqsasxYT6+YN5G8i7Ydi2h2cdI7ifWwETuuMrq1coSffTwsc3dXpsHr9SK8DcpDFrtq8J hiXRr/4g==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:43970) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1vjOlV-000000002YU-2dTD; Fri, 23 Jan 2026 21:32:25 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.98.2) (envelope-from ) id 1vjOlR-000000002QA-2jQL; Fri, 23 Jan 2026 21:32:21 +0000 Date: Fri, 23 Jan 2026 21:32:21 +0000 From: "Russell King (Oracle)" To: Mohd Ayaan Anwar Cc: Andrew Lunn , Heiner Kallweit , Alexandre Torgue , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Konrad Dybcio , linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-phy@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, Maxime Coquelin , Neil Armstrong , netdev@vger.kernel.org, Paolo Abeni , Vinod Koul Subject: Re: [PATCH net-next v2 00/14] net: stmmac: SerDes, PCS, BASE-X, and inband goodies Message-ID: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Russell King (Oracle) On Fri, Jan 23, 2026 at 07:05:00PM +0530, Mohd Ayaan Anwar wrote: > 4. Switching from 1G to 2.5G - similar issues + a NULL pointer > dereference. I am checking on the reason for it. For the NULL pointer dereference, this is a bit weird, and may help to point towards the issue. > [ 1235.996004] qcom-ethqos 23040000.ethernet eth1: phy link down 2500base-x/Unknown/Unknown/none/off/nolpi > [ 1240.517716] qcom-ethqos 23040000.ethernet eth1: phy link up 2500base-x/2.5Gbps/Full/none/off/nolpi > [ 1240.529470] qcom-ethqos 23040000.ethernet eth1: major config, requested phy/2500base-x > [ 1240.537642] qcom-ethqos 23040000.ethernet eth1: interface 2500base-x inband modes: pcs=00 phy=00 > [ 1240.546702] qcom-ethqos 23040000.ethernet eth1: major config, active phy/outband/2500base-x > [ 1240.555441] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010 > [ 1240.880168] Code: d63f0020 f9400e60 b4000040 f900081f (f9000ad3) This code line disassembles to: 0: d63f0020 blr x1 4: f9400e60 ldr x0, [x19, #24] 8: b4000040 cbz x0, 10 <.text+0x10> c: f900081f str xzr, [x0, #16] 10: f9000ad3 str x19, [x22, #16] which, after comparing with my disassembly, the blr x1 is the call to pcs_disable() inside phylink_pcs_disable() in this code: if (pcs_changed) { phylink_pcs_disable(pl->pcs); if (pl->pcs) pl->pcs->phylink = NULL; pcs->phylink = pl; and the failing store is the one for that last line of C code - in other words, pcs = NULL. This means that mac_select_pcs() returned NULL when being asked "which PCS should be used for 2500base-X" ? This suggests that the SerDes detection of support for 2500BASE-X isn't working, meaning that stmmac_mac_select_pcs() ends up returning NULL, rather than &priv->integrated_pcs->pcs. That would only happen if: /* Only allow 2500Base-X if the SerDes has support. */ ret = dwmac_serdes_validate(priv, PHY_INTERFACE_MODE_2500BASEX); if (ret == 0) __set_bit(PHY_INTERFACE_MODE_2500BASEX, spcs->pcs.supported_interfaces); fails, meaning we don't set that interface mode for the PCS. dwmac_serdes_validate() calls phy_validate() for PHY_MODE_ETHERNET with the PHY interface mode as the sub mode. Patch 3 adds the required methods to phy-qcom-sgmii-eth.c to allow phy_validate() to indicate whether this is supported or not: .validate = qcom_dwmac_sgmii_phy_validate, and its implementation is: int ret = qcom_dwmac_sgmii_phy_speed(mode, submode); return ret < 0 ? ret : 0; where qcom_dwmac_sgmii_phy_speed() is: if (mode != PHY_MODE_ETHERNET) return -EINVAL; if (submode == PHY_INTERFACE_MODE_SGMII || submode == PHY_INTERFACE_MODE_1000BASEX) return SPEED_1000; if (submode == PHY_INTERFACE_MODE_2500BASEX) return SPEED_2500; return -EINVAL; So, this should be returning a positive integer (SPEED_2500), which should cause phy_validate(serdes, PHY_MODE_ETHERNET, PHY_INTERFACE_MODE_2500BASEX, NULL) to return success (zero). That should result in PHY_INTERFACE_MODE_2500BASEX being set in spcs->pcs.supported_interfaces, and thus &priv->integrated_pcs->pcs being returned for PHY_INTERFACE_MODE_2500BASEX. Is the particular hardware you're running this oopsing test on not using a SerDes PHY? If that's the case, how does it switch between 2.5Gbps and 1Gbps data rate on the SerDes? -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!