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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 36787ECAAD8 for ; Fri, 16 Sep 2022 09:56:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230273AbiIPJ4K (ORCPT ); Fri, 16 Sep 2022 05:56:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42694 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230051AbiIPJ4H (ORCPT ); Fri, 16 Sep 2022 05:56:07 -0400 Received: from lelv0143.ext.ti.com (lelv0143.ext.ti.com [198.47.23.248]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9CD4FA74D1; Fri, 16 Sep 2022 02:56:05 -0700 (PDT) Received: from fllv0035.itg.ti.com ([10.64.41.0]) by lelv0143.ext.ti.com (8.15.2/8.15.2) with ESMTP id 28G9tcQ3065273; Fri, 16 Sep 2022 04:55:38 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1663322138; bh=3UE0aBXJzijV4j63hDjBLnZQXGBaoaq9ZOB+7kpHIhc=; h=Date:CC:Subject:To:References:From:In-Reply-To; b=wmhftObzH6kVA2WcpETW3INNxPYY+kGrYEUiuqvQjfBNTq4PBjHwiWRsfMgFB1Z7u 4K5UxT+7kHfHFjuv/WK87GsDmPXkbh9EhVFxoscQbs2AIHY88rX8Ag2WKTYaDzXWm6 HqRKjxYFdJuZh0MkwcAGeEpYRUvIbJhAieKmPW9U= Received: from DFLE111.ent.ti.com (dfle111.ent.ti.com [10.64.6.32]) by fllv0035.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 28G9tcL2002869 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 16 Sep 2022 04:55:38 -0500 Received: from DFLE111.ent.ti.com (10.64.6.32) by DFLE111.ent.ti.com (10.64.6.32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2507.6; Fri, 16 Sep 2022 04:55:38 -0500 Received: from lelv0327.itg.ti.com (10.180.67.183) by DFLE111.ent.ti.com (10.64.6.32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2507.6 via Frontend Transport; Fri, 16 Sep 2022 04:55:38 -0500 Received: from [10.24.69.241] (ileaxei01-snat2.itg.ti.com [10.180.69.6]) by lelv0327.itg.ti.com (8.15.2/8.15.2) with ESMTP id 28G9tWld015902; Fri, 16 Sep 2022 04:55:33 -0500 Message-ID: <5be6de72-ba90-472e-7714-93940260b2ae@ti.com> Date: Fri, 16 Sep 2022 15:25:32 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 CC: , , , , , , , , , , , , , , , , Subject: Re: [PATCH 5/8] net: ethernet: ti: am65-cpsw: Add support for fixed-link configuration Content-Language: en-US To: "Russell King (Oracle)" References: <20220914095053.189851-1-s-vadapalli@ti.com> <20220914095053.189851-6-s-vadapalli@ti.com> <85398274-c0fb-6ef6-29b3-ad8d2465f8e4@ti.com> From: Siddharth Vadapalli In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Russell, On 16/09/22 14:44, Russell King (Oracle) wrote: > On Fri, Sep 16, 2022 at 02:33:23PM +0530, Siddharth Vadapalli wrote: >> Hello Russell, >> >> On 16/09/22 12:50, Russell King (Oracle) wrote: >>> SGMII is designed for the setup in the diagram I provided in my previous >>> email. It is not designed for two MACs to talk direct to each other >>> without any ethernet PHY because of the asymmetric nature of the control >>> word. >>> >>> The PHY sends e.g. a control word of 0x9801 for 1G full duplex. On >>> reception of that, the MAC responds with 0x4001. Finally, the PHY >>> responds with 0xd801 to acknowledge the receipt of the MAC response. >>> >>> If both ends of the link are SGMII, both ends will be waiting for >>> the control word from a PHY which is not present, and the link will >>> not come up. >>> >>> 1000base-X is a symmetric protocol where both ends of the link >>> advertise their capabilities, acknowledge each others abilities and >>> resolve the duplex and pause settings. >>> >>> SGMII is a Cisco proprietary modification of 1000base-X designed for >>> communicating the results of media autonegotiation between an >>> ethernet PHY and ethernet MAC. >> >> I will try to implement and test SGMII mode in the conventional way with >> both the MAC and the PHY present. If I am unable to do so, I will revert >> to the current set of patches for the special case where the MAC >> emulates a PHY, and mention this setup in the commit message of the v2 >> series. I hope this approach would be fine to proceed with. Please let >> me know in case of any suggestions. > > What exact setups are you trying to support with this patch set? > > If you're looking to only add support for SGMII, then all you need > to do is to make sure it works with a PHY. Fixed-link in SGMII only > makes sense if you're directly connected to something like a network > switch, but even then, network switches tend to use 1000base-X in a > fixed-link mode rather than SGMII. I plan to support the standard MAC2PHY based SGMII mode. However, the SGMII ethernet PHY that I have with me has issues which is why I had tried the unconventional fixed-link SGMII mode with the MAC emulating the ethernet PHY. I will try to obtain a functional SGMII ethernet PHY and test the standard SGMII mode. Thank you for patiently answering my questions and helping me understand the SGMII mode better :) Regards, Siddharth.