From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753589AbdDKXXp (ORCPT ); Tue, 11 Apr 2017 19:23:45 -0400 Received: from mail-pg0-f54.google.com ([74.125.83.54]:36792 "EHLO mail-pg0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752547AbdDKXXj (ORCPT ); Tue, 11 Apr 2017 19:23:39 -0400 Subject: Re: [RFC net-next] of: mdio: Honor hints from MDIO bus drivers To: Andrew Lunn References: <20170410214258.9409-1-f.fainelli@gmail.com> <8ef102a4-22e5-def8-b50e-04f84b5849d7@gmail.com> <20170411231424.GA6174@lunn.ch> Cc: netdev@vger.kernel.org, davem@davemloft.net, Rob Herring , Frank Rowand , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" , open list From: Florian Fainelli Message-ID: <6de72d4c-5634-f3d6-5bfd-fcc0acda0b83@gmail.com> Date: Tue, 11 Apr 2017 16:23:25 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20170411231424.GA6174@lunn.ch> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/11/2017 04:14 PM, Andrew Lunn wrote: >> To give some more background and rational for this change. >> >> On a platform where we have a parent MDIO bus, backed by the >> mdio-bcm-unimac.c driver, we also register a slave MII bus (through >> net/dsa/dsa2.c) which is parented to this UniMAC MDIO bus through an >> assignment of of_node. This slave MII bus is created in order to >> intercept reads/writes to problematic addresses (e.g: that clashes with >> another piece of hardware). >> >> This means that the slave DSA MII bus inherits all child nodes from the >> originating master MII bus. This also means that when the slave MII bus >> is probed via of_mdiobus_register(), we probe the same devices twice: >> once through the master, another time through the slave. > > Ah, O.K. This makes more sense. On the hardware i have, we get three > deep in MDIO busses. We have the FEC mdio bus. On top of that we have > a gpio-mux-mdio, and on top of that we have the mv88e6xxx mdio > bus. And i've never seen issues. > > So your real problem here is you have two mdio busses using the same > device tree properties. I would actually say that is just plain > broken. >>From a Device Tree/HW representation perspective, we do have the external BCM53125 switch physically attached to the 7445/7278 SWITCH_MDIO bus (backed by mdio-bcm-unimac) so in that regard the representation is correct. There is also an integrated Gigabit PHY (bcm7xxx) which is attached to that bus. >>From a SW perspective though, we want to talk to the integrated Gigabit PHY using mdio-bcm-unimac but talk to the external BCM53125 switch using the slave MII bus created by the bcm_sf2 driver in order to create an isolation. We need to inherit some of the parent (mdio-bcm-unimac) child DT nodes (such as the BCM53125), but not the GPHY. The easiest solution I found was to use this patch. Using mdiobus_register() instead of of_mdiobus_register() was considered, but then, the child BCM53125 has no more "visbility" into the OF world at all, and it matters, because this switch is also driven via a DSA switch driver and its Ethernet data-path is connected to one port of the bcm_sf2 switch.. Thankfully the HW bug was fixed eventually ;) -- Florian