From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Cochran Subject: Configuring synchronous ethernet with ethtool? Date: Tue, 17 Mar 2015 17:11:28 +0100 Message-ID: <20150317161128.GA8793@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: netdev@vger.kernel.org Return-path: Received: from mail-we0-f178.google.com ([74.125.82.178]:34255 "EHLO mail-we0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753451AbbCQQLd (ORCPT ); Tue, 17 Mar 2015 12:11:33 -0400 Received: by wegp1 with SMTP id p1so11482113weg.1 for ; Tue, 17 Mar 2015 09:11:32 -0700 (PDT) Received: from localhost.localdomain (88-117-31-137.adsl.highway.telekom.at. [88.117.31.137]) by mx.google.com with ESMTPSA id ax10sm20547980wjc.26.2015.03.17.09.11.30 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Tue, 17 Mar 2015 09:11:31 -0700 (PDT) Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Dear list, I need to configure Synchronous Ethernet (SyncE) on a per-port basis for a current project. So, I have been thinking about how best to implement SyncE. My first idea is to make this into a new ethtool operation, but I would like to get some feedback about the direction. Apart from ITU-T G.8261, 8262, and 8264, which are not too helpful, I could hardly find any documentation at all about how SyncE is supposed to work. My current understanding is limited to: * 100 Mbit - Each link partner generates its own transmit clocks. - There is at least one 100 Mbit PHY that allows using the recovered clock from the link partner for the PHY's own transmit clock. (SyncE slave mode) * 1000 Mbit - With 1000 Mbit, only one of the link partners generates a clock. The decision of which link partner becomes the clock master is a normal part of the Gigabit protocol. - One switch I have worked with has per-port bits that allow setting MASTER/SLAVE and MANUAL/PREFERRED. I am not sure what the "preferred" modes does. So, my current idea is to have an ethtool option to set the SyncE mode to one of: - master (1000 Mbit only) - slave - none I am not sure whether the manual/preferred thing makes any sense. Maybe someone has insight into this? Thoughts? Thanks, Richard