From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5C902CF8853 for ; Fri, 4 Oct 2024 17:25:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id: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-Owner; bh=r7K5K/qZvjgIES+9JYIIHa7wXSVw+xS1RUWhZQdScQs=; b=x/Vwq+Msd+jZlF/kkwivTwZXqk eiq2VkhEyADIOt0kxq2BBFPjaBuz2qCyZfhUMSUwVPDbfMo/wzWlIP61+2LdbBalIngQI80d3EkKn hEkmJfFlAtuIPThtpQQ6qz5gB3UJ2VUc29UmfeVMDAaBP6KZ8nFXYf29oBz8E6MLjA+qF33OBVhFu wtcDlDWEYuvaDFljxrqwfxqeVfE5hDa8LzdOJrLpeCPT2EecIPfbhK2o9K/U9noNAUFQ9HUNeg0ms v7TM+LkxaZHPgUxdOD7oxG7kj+/1LEiEmlQseqJ6mSc7hOjwA7CmLFbnM+QEeR3wO6Gj/Co2ULBDw 5pOegtkQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1swm3A-0000000DVge-47Ys; Fri, 04 Oct 2024 17:25:09 +0000 Received: from pandora.armlinux.org.uk ([2001:4d48:ad52:32c8:5054:ff:fe00:142]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1swlhZ-0000000DNJ3-3qB7 for linux-arm-kernel@lists.infradead.org; Fri, 04 Oct 2024 17:02:51 +0000 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=r7K5K/qZvjgIES+9JYIIHa7wXSVw+xS1RUWhZQdScQs=; b=daUGP8qdLRq371XdEShyVcnIgH Pf2bscR0Nb6nXVatopZRGBuDWqlPpqwDO9/Nb4kviP+OqEPYGIKYz/FgXrOqJ2s3y8dq4LYpK1qHc mNzujeLtirLaws3pks6IL9xlZ10Vq3OsN2LQD7ZQu9yn5cZNJsWlnZvzVdxQHJRxcNnGLvC+m37xQ g/E++jKdUytUTl8V7mH+rNcioumMiLaJDnLO/PYYiFnCe7njDPffwk3wOl6W+ds+OsxkAuHW0JUjV 1GMZIyfw1oj4Ouw6Mrj7MpTIMJegnXLnbE0lII6gCqBoJ9p3jnFXIeWZlrM6Yss/F9V8wSzdHmqd8 FuS/39jA==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:51482) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1swlhK-0002K5-25; Fri, 04 Oct 2024 18:02:36 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.96) (envelope-from ) id 1swlhB-0001KJ-33; Fri, 04 Oct 2024 18:02:26 +0100 Date: Fri, 4 Oct 2024 18:02:25 +0100 From: "Russell King (Oracle)" To: Maxime Chevallier Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, thomas.petazzoni@bootlin.com, Andrew Lunn , Jakub Kicinski , Eric Dumazet , Paolo Abeni , linux-arm-kernel@lists.infradead.org, Christophe Leroy , Herve Codina , Florian Fainelli , Heiner Kallweit , Vladimir Oltean , Marek =?iso-8859-1?Q?Beh=FAn?= , =?iso-8859-1?Q?K=F6ry?= Maincent , Oleksij Rempel Subject: Re: [PATCH net-next v2 0/9] Allow isolating PHY devices Message-ID: References: <20241004161601.2932901-1-maxime.chevallier@bootlin.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241004161601.2932901-1-maxime.chevallier@bootlin.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241004_100249_979703_31D1AB9B X-CRM114-Status: GOOD ( 28.85 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org I'm going to ask a very basic question concerning this. Isolation was present in PHYs early on when speeds were low, and thus electrical reflections weren't too much of a problem, and thus star topologies didn't have too much of an effect. A star topology is multi-drop. Even if the PCB tracks go from MAC to PHY1 and then onto PHY2, if PHY2 is isolated, there are two paths that the signal will take, one to MAC and the other to PHY2. If there's no impediance match at PHY2 (e.g. because it's in high-impedance mode) then that transmission line is unterminated, and thus will reflect back towards the MAC. As speeds get faster, then reflections from unterminated ends become more of an issue. I suspect the reason why e.g. 88x3310, 88E1111 etc do not support isolate mode is because of this - especially when being used in serdes mode, the topology is essentially point-to-point and any side branches can end up causing data corruption. So my questions would be, is adding support for isolation mode in PHYs given todays network speeds something that is realistic, and do we have actual hardware out there where there is more than one PHY in the bus. If there is, it may be useful to include details of that (such as PHY interface type) in the patch series description. On Fri, Oct 04, 2024 at 06:15:50PM +0200, Maxime Chevallier wrote: > Hello, > > This is the V2 of a series to add isolation support for PHY devices. > > As a remainder, this mode allows a PHY to set its MII lines in > high-impedance mode to avoid interferences on this bus. > > So far, I've identified that : > > - Marvell 88e1512 isolation works fine > - LXT973 claims to support isolation, but it's actually broken > - Marvell 88x3310 doesn't support isolation, by design > - Marvell 88e1111 claims to support isolation in GMII, RGMII, TBI > (untested) but doesn't in SGMII (tested). > > Changes in V2 : > > - Removed the loopback mode that was included in the first iteration > - Added phy_shutdown, to make sure we de-isolate the PHY when rebooting > - Changes the "PHY_NO_ISOLATE" flag to a phy driver ops. Testing showed > that some PHYs may or may not support isolation based on the > interface that's being used. > - Added isolation support reporting for the Marvell 88e1111 PHY. > > V1 : https://lore.kernel.org/netdev/20240911212713.2178943-1-maxime.chevallier@bootlin.com/ > > Maxime Chevallier (9): > net: phy: allow isolating PHY devices > net: phy: Introduce phy_shutdown for device quiescence. > net: phy: Allow PHY drivers to report isolation support > net: phy: lxt: Mark LXT973 PHYs as having a broken isolate mode > net: phy: marvell10g: 88x3310 and 88x3340 don't support isolate mode > net: phy: marvell: mv88e1111 doesn't support isolate in SGMII mode > net: phy: introduce ethtool_phy_ops to get and set phy configuration > net: ethtool: phy: allow reporting and setting the phy isolate status > netlink: specs: introduce phy-set command along with configurable > attributes > > Documentation/netlink/specs/ethtool.yaml | 15 +++ > Documentation/networking/ethtool-netlink.rst | 1 + > drivers/net/phy/lxt.c | 2 + > drivers/net/phy/marvell.c | 9 ++ > drivers/net/phy/marvell10g.c | 2 + > drivers/net/phy/phy.c | 44 ++++++++ > drivers/net/phy/phy_device.c | 101 +++++++++++++++++-- > include/linux/ethtool.h | 8 ++ > include/linux/phy.h | 42 ++++++++ > include/uapi/linux/ethtool_netlink.h | 2 + > net/ethtool/netlink.c | 8 ++ > net/ethtool/netlink.h | 1 + > net/ethtool/phy.c | 68 +++++++++++++ > 13 files changed, 297 insertions(+), 6 deletions(-) > > -- > 2.46.1 > > -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!