From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755444AbeCSMwd (ORCPT ); Mon, 19 Mar 2018 08:52:33 -0400 Received: from mail.bootlin.com ([62.4.15.54]:57984 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754892AbeCSMw3 (ORCPT ); Mon, 19 Mar 2018 08:52:29 -0400 Date: Mon, 19 Mar 2018 13:52:27 +0100 From: Antoine Tenart To: Russell King - ARM Linux Cc: Antoine Tenart , davem@davemloft.net, kishon@ti.com, gregory.clement@bootlin.com, andrew@lunn.ch, jason@lakedaemon.net, sebastian.hesselbarth@gmail.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, thomas.petazzoni@bootlin.com, maxime.chevallier@bootlin.com, miquel.raynal@bootlin.com, nadavh@marvell.com, stefanc@marvell.com, ymarkman@marvell.com, mw@semihalf.com, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH net-next 02/10] net: phy: phylink: allow 10GKR interface to use in-band negotiation Message-ID: <20180319125227.GI4519@kwain> References: <20180316103351.16616-1-antoine.tenart@bootlin.com> <20180316103351.16616-3-antoine.tenart@bootlin.com> <20180316155307.GQ9418@n2100.armlinux.org.uk> <20180319085252.GF4519@kwain> <20180319111205.GB2743@n2100.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180319111205.GB2743@n2100.armlinux.org.uk> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Russell, On Mon, Mar 19, 2018 at 11:12:05AM +0000, Russell King - ARM Linux wrote: > On Mon, Mar 19, 2018 at 09:52:52AM +0100, Antoine Tenart wrote: > > > > Anyway, the reason to use in-band negotiation was also to avoid using > > fixed-link. It would work but always report the link is up, which for > > the user isn't a great experience as we have a way to detect this. > > > > What would you suggest to achieve this in a reasonable way? > > The intention of this test in phylink_of_phy_connect() is to avoid > failing when there is no requirement for a PHY to be present (such as > a fixed link, or an 802.3z link.) However, with 10G PHYs such as the > 3310, we need the PHY so we can read the speed from it, and so know > whether to downgrade the MAC to SGMII mode, or having downgraded the > MAC, upgrade it back to 10G mode when the PHY switches to 10G. > > I'm guessing that you're wanting this for the DB boards, but I don't > see why. Do they not have PHYs? You guessed right, that's exactly my use case. The DB boards (7k and 8k) have 10G interfaces without PHYs. I could describe them as fixed-link (it works), but it would be better not to require a PHY in phylink_of_phy_connect() for such interfaces. That's why I used in-band AN, which is wrong, but we still probably need to add a check to allow such setups. I'm all ears for suggestions as I do not have the full picture of all the supported modes and their requirements. Thanks! Antoine -- Antoine Ténart, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com