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_1 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 7F70BC433E0 for ; Tue, 9 Jun 2020 12:11:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6863C2078D for ; Tue, 9 Jun 2020 12:11:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729245AbgFIMLf (ORCPT ); Tue, 9 Jun 2020 08:11:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45516 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729094AbgFIMLf (ORCPT ); Tue, 9 Jun 2020 08:11:35 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20164C05BD1E for ; Tue, 9 Jun 2020 05:11:35 -0700 (PDT) Received: from ptx.hi.pengutronix.de ([2001:67c:670:100:1d::c0]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1jid6K-0007sT-3d; Tue, 09 Jun 2020 14:11:32 +0200 Received: from sha by ptx.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1jid6J-0005En-9w; Tue, 09 Jun 2020 14:11:31 +0200 Date: Tue, 9 Jun 2020 14:11:31 +0200 From: Sascha Hauer To: Russell King - ARM Linux admin Cc: netdev@vger.kernel.org, devicetree@vger.kernel.org, kernel@pengutronix.de, linux-kernel@vger.kernel.org, Thomas Petazzoni , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] net: ethernet: mvneta: add support for 2.5G DRSGMII mode Message-ID: <20200609121131.GJ11869@pengutronix.de> References: <20200608074716.9975-1-s.hauer@pengutronix.de> <20200608160801.GO1551@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200608160801.GO1551@shell.armlinux.org.uk> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 09:53:29 up 110 days, 15:23, 126 users, load average: 0.02, 0.10, 0.13 User-Agent: Mutt/1.10.1 (2018-07-13) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: sha@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: devicetree@vger.kernel.org Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Mon, Jun 08, 2020 at 05:08:01PM +0100, Russell King - ARM Linux admin wrote: > On Mon, Jun 08, 2020 at 09:47:16AM +0200, Sascha Hauer wrote: > > The Marvell MVNETA Ethernet controller supports a 2.5 Gbps SGMII mode > > called DRSGMII. > > > > This patch adds a corresponding phy-mode string 'drsgmii' and parses it > > from DT. The MVNETA then configures the SERDES protocol value > > accordingly. > > > > It was successfully tested on a MV78460 connected to a FPGA. > > Digging around, this is Armada XP? Which SoCs is this mode supported? > There's no mention of DRSGMII in the A38x nor A37xx documentation which > are later than Armada XP. It's an Armada XP MV78460 in my case. I have no idea what other SoCs this mode is supported on. > > What exactly is "drsgmii"? It can't be "double-rate" SGMII because that > would give you 2Gbps max instead of the 1Gbps, but this gives 2.5Gbps, > so I'm really not sure using "drsgmii" is a good idea. It may be what > Marvell call it, but we really need to know if there's some vendor > neutral way to refer to it. The abbreviation really is for "Double Rated SGMII". It seems it has 2.5 times the clock rate than ordinary SGMII. Another term I found is HSGMII (High serial gigabit media-independent interface) which also has 2.5Gbps. Anyway, I just learned from the paragraph you added to Documentation/networking/phy.rst that 1000BASEX differs from SGMII in the format of the control word. As we have a fixed link to a FPGA the control word seems to be unused, at least the Port MAC Control Register0 PortType setting bit doesn't change anything. So I can equally well use the existing 2500BASEX mode. Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |