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 X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C7A1CC54FD0 for ; Wed, 25 Mar 2020 10:35:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A79952077D for ; Wed, 25 Mar 2020 10:35:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727621AbgCYKfp (ORCPT ); Wed, 25 Mar 2020 06:35:45 -0400 Received: from protonic.xs4all.nl ([83.163.252.89]:39992 "EHLO protonic.nl" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727407AbgCYKfo (ORCPT ); Wed, 25 Mar 2020 06:35:44 -0400 X-Greylist: delayed 409 seconds by postgrey-1.27 at vger.kernel.org; Wed, 25 Mar 2020 06:35:43 EDT Received: from erd988 (erd988.prtnl [192.168.224.30]) by sparta.prtnl (Postfix) with ESMTP id A803844A024D; Wed, 25 Mar 2020 11:28:52 +0100 (CET) Date: Wed, 25 Mar 2020 11:28:51 +0100 From: David Jander To: Russell King - ARM Linux admin Cc: Oleksij Rempel , David Miller , andrew@lunn.ch, f.fainelli@gmail.com, hkallweit1@gmail.com, mark.rutland@arm.com, robh+dt@kernel.org, kernel@pengutronix.de, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, marex@denx.de, devicetree@vger.kernel.org, olteanv@gmail.com Subject: Re: user space interface for configuring T1 PHY management mode (master/slave) Message-ID: <20200325112851.43b3e6bc@erd988> In-Reply-To: <20200325101111.GZ25745@shell.armlinux.org.uk> References: <20200325083449.GA8404@pengutronix.de> <20200325101111.GZ25745@shell.armlinux.org.uk> Organization: Protonic Holland X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, 25 Mar 2020 10:11:12 +0000 Russell King - ARM Linux admin wrote: > On Wed, Mar 25, 2020 at 09:34:49AM +0100, Oleksij Rempel wrote: > > Hi all, > > > > I'm working on mainlining of NXP1102 PHY (BroadR Reach/802.3bw) support. > > > > Basic functionality is working and support with mainline kernel. Now it is > > time to extend it. According to the specification, each PHY can be master > > or slave. > > > > The HW can be pre configured via bootstrap pins or fuses to have a default > > configuration. But in some cases we still need to be able to configure the > > PHY in a different mode: > > -------------------------------------------------------------------------------- > > http://www.ieee802.org/3/1TPCESG/public/BroadR_Reach_Automotive_Spec_V3.0.pdf > > > > 6.1 MASTER-SLAVE configuration resolution > > > > All BroadR-Reach PHYs will default to configure as SLAVE upon power up or > > reset until a management system (for example, processor/microcontroller) > > configures it to be MASTER. MASTER-SLAVE assignment for each link > > configuration is necessary for establishing the timing control of each PHY. > > > > 6.2 PHY-Initialization > > > > Both PHYs sharing a link segment are capable of being MASTER or SLAVE. In > > IEEE 802.3-2012, MASTER-SLAVE resolution is attained during the > > Auto-Negotiation process (see IEEE 802.3-2012 Clause 28). However, the > > latency for this process is not acceptable for automotive application. A > > forced assignment scheme is employed depending on the physical deployment > > of the PHY within the car. This process is conducted at the power-up or > > reset condition. The station management system manually configures the > > BroadR-Reach PHY to be MASTER (before the link acquisition process starts) > > while the link partner defaults to SLAVE (un-managed). > > -------------------------------------------------------------------------------- > > > > Should phylink be involved in this configuration? What's the proper user > > space interface to use for this kind of configuration? ethtool or ip > > comes into mind. Further having a Device Tree property to configure a > > default mode to overwrite the boot strap pins would be nice to have. > > Well, the first question would be whether this is something that > userspace needs to alter, or whether static configuration at boot > time is what is necessary. > > Given what is in the description, it seems that the concern is with > the latency it takes for the link to come up. I would suggest that > the lowest latency would be achieved when using static configuration > rather than waiting for the kernel to fully boot and userspace to > start before configuring the PHY. Yes, that would be the fastest, and in many cases the preferred way. But the lack of auto negotiation is not a choice. It is imposed by the spec. Because of this, and since the PHY's are configurable in software, there is some need for configuration in user-space. Of course latency would not be an issue in such a case, otherwise a fixed strapped configuration was chosen. Best regards, -- David Jander Protonic Holland.