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 8E926500942; Fri, 9 Jan 2026 21:32:34 +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=1767994356; cv=none; b=Mtj92UvDE1usf3jrsDQIVwWdisRAJL7dRTauCVQCbZyEzDEuJ2EH98jFXdQWFVibOQjHKsBmc+OUyQ4JPOrXG9Bjc8DBWYpd8olE1vuCJk8WplrkjkURI0wYCd0PJbJmILpG2fc4A9YK7dAAY7AzKHr3L3SYBzse0tikVhkezxY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767994356; c=relaxed/simple; bh=fat2CoC7ZD57Pu0XLNkO1+A5yeIHqj50mpWtl2XZLtI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=IFA6pBuHygOpTEvnn5dOo7SNHVXvjfLk0DrOKwbIzHFQfzjfWerdUgYNzGYpAKkauOKbzZtVsBcvUaRs9zp8pMTz2heSynXvylsZJVBdnFy7esaqNvHnsIdKQ7QYMxXTRolvm7XrL2UbufkMt9u9l147QNYwQzIq9w+TmTVyqiQ= 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=Da9RZUY0; 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="Da9RZUY0" 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=/nDQg9bpXjHmVcghjS2F7GZEWZqr2lL6ZJYKc/GvqCA=; b=Da9RZUY0CnXx47/5MElY2eW2+8 fLTGpcDUgoxlZ5CiTDYeUwsc98LU3MUIu7PtL54otK/eEPnnTEmP/Fh6yq2Ln1qpuT5u7UKyx3GYK F9vfpHm5J45d6ymZGNdI5wnAo7xcha7rHyRfpjOWjYQQCTBqcEmejV7P9SnH+ZcS4wDLNwr/lAB5N abVpU3UkNqPnDM4Nq3woPGY78DzlTMxmbaZlulk3fLzZXlFvfhy+IKfx2Ym+M2Bn6GeK2xwB061st PUeibgU5OoqszN/Q7TBnGoPhsrDrz2gqeWIVDOcWhJhMOblJ+J5xoUTO92CRWQgJdM/Urmc0xkKST ZOUDm5ug==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:56288) 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 1veK5m-000000004M5-3hoR; Fri, 09 Jan 2026 21:32:23 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.98.2) (envelope-from ) id 1veK5i-000000003e9-0k86; Fri, 09 Jan 2026 21:32:18 +0000 Date: Fri, 9 Jan 2026 21:32:18 +0000 From: "Russell King (Oracle)" To: Daniel Golle Cc: Andrew Lunn , Heiner Kallweit , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Vladimir Oltean , Michael Klein , Aleksander Jan Bajkowski , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 2/5] net: phy: realtek: simplify C22 reg access via MDIO_MMD_VEND2 Message-ID: References: <938aff8b65ea84eccdf1a2705684298ec33cc5b0.1767926665.git.daniel@makrotopia.org> 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=us-ascii Content-Disposition: inline In-Reply-To: <938aff8b65ea84eccdf1a2705684298ec33cc5b0.1767926665.git.daniel@makrotopia.org> Sender: Russell King (Oracle) On Fri, Jan 09, 2026 at 03:03:22AM +0000, Daniel Golle wrote: > RealTek 2.5GE PHYs have all standard Clause-22 registers mapped also > inside MDIO_MMD_VEND2 at offset 0xa400. This is used mainly in case the > PHY is inside a copper SFP module which uses the RollBall MDIO-over-I2C > method which *only* supports Clause-45. It isn't just Rollball. There are SoCs out there which have separate MDIO buses, one bus signals at 3.3V and can generate only clause 22 frames. The other operates at 1.2V and can only generate clause 45 frames. While hardware may elect to generate and recognise either frame types at either voltage, this goes some way to explain why there are implementations that only support one or the other on a particular pair of MDC/MDIO wires. Armada 8040 has this setup - there is one MDIO bus that only supports clause 22 frames, and there is a separate MDIO bus that only supports clause 45 frames. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!