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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 84929C433DB for ; Thu, 25 Feb 2021 13:15:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3222464EBD for ; Thu, 25 Feb 2021 13:15:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231771AbhBYNPB (ORCPT ); Thu, 25 Feb 2021 08:15:01 -0500 Received: from vps0.lunn.ch ([185.16.172.187]:57390 "EHLO vps0.lunn.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230019AbhBYNPA (ORCPT ); Thu, 25 Feb 2021 08:15:00 -0500 Received: from andrew by vps0.lunn.ch with local (Exim 4.94) (envelope-from ) id 1lFGTA-008PLw-E7; Thu, 25 Feb 2021 14:14:16 +0100 Date: Thu, 25 Feb 2021 14:14:16 +0100 From: Andrew Lunn To: Joakim Zhang Cc: Florian Fainelli , netdev , dl-linux-imx Subject: Re: [PATCH V1 net-next 0/3] net: stmmac: implement clocks Message-ID: References: <20210223104818.1933-1-qiangqing.zhang@nxp.com> <20210223084503.34ae93f7@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <20210223175441.2a1b86f1@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org > Hi Andrew, > > Thanks for you explanation, I still don't quite understand what the use case it is, could you give me more details, thanks a lot! > AFAIK now, there are two connections methods, we can abstract the layer: > MAC <-> MAC, there is no PHY attached. It seems to know as Fixed link, right? Yes, this is the most common way of connecting a switch. > MAC+PHY <-> PHY+MAC Switches can be connected like this, but not often. Why pay for two PHYs which you do not need? > From your expression, you should use an external Ethernet switch, if > yes, why Ethernet switch needs to use MDIO bus to access another > MAC's(STMMAC) PHY? The switch is on the same board as the MAC. Take a look at: https://netdevconf.info/2.1/papers/distributed-switch-architecture.pdf It explains the DSA architecture. Andrew