From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752457AbeEQPCN (ORCPT ); Thu, 17 May 2018 11:02:13 -0400 Received: from pandora.armlinux.org.uk ([78.32.30.218]:60334 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751468AbeEQPCL (ORCPT ); Thu, 17 May 2018 11:02:11 -0400 Date: Thu, 17 May 2018 16:01:55 +0100 From: Russell King - ARM Linux To: Andrew Lunn Cc: Antoine Tenart , davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, thomas.petazzoni@bootlin.com, maxime.chevallier@bootlin.com, gregory.clement@bootlin.com, miquel.raynal@bootlin.com, nadavh@marvell.com, stefanc@marvell.com, ymarkman@marvell.com, mw@semihalf.com Subject: Re: [PATCH net-next 1/2] net: phy: sfp: make the i2c-bus property really optional Message-ID: <20180517150155.GB17671@n2100.armlinux.org.uk> References: <20180517082907.14420-1-antoine.tenart@bootlin.com> <20180517082907.14420-2-antoine.tenart@bootlin.com> <20180517124127.GG8547@lunn.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180517124127.GG8547@lunn.ch> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 17, 2018 at 02:41:28PM +0200, Andrew Lunn wrote: > On Thu, May 17, 2018 at 10:29:06AM +0200, Antoine Tenart wrote: > > The SFF,SFP documentation is clear about making all the DT properties, > > with the exception of the compatible, optional. In practice this is not > > the case and without an i2c-bus property provided the SFP code will > > throw NULL pointer exceptions. > > > > This patch is an attempt to fix this. > > Hi Antoine, Russell > > How usable is an SFF/SFP module without access to the i2c EEPROM? I > guess this comes down to link speed. Can it be manually configured? While we can support forcing the speed/duplex through ethtool, there is no obvious facility via ethtool to set the protocol currently (eg, SGMII vs 1000base-X). There is, however, the possibility to use the advertise mask to determine which mode we should be using, but that's awkward to deal with via ethtool as ethtool wants a hex mask, which really isn't user friendly. The protocol matters - for example, a copper SFP module will typically want to use SGMII, and if it encounters 1000base-X on the other side, the PHY won't pass data because it will believe that the link to the MAC is down. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up According to speedtest.net: 8.21Mbps down 510kbps up