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 EA21DC433F5 for ; Mon, 21 Mar 2022 11:46:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346831AbiCULrl (ORCPT ); Mon, 21 Mar 2022 07:47:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56766 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241385AbiCULrj (ORCPT ); Mon, 21 Mar 2022 07:47:39 -0400 Received: from ssl.serverraum.org (ssl.serverraum.org [IPv6:2a01:4f8:151:8464::1:2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2202A113D08; Mon, 21 Mar 2022 04:46:14 -0700 (PDT) Received: from ssl.serverraum.org (web.serverraum.org [172.16.0.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id 50BC922175; Mon, 21 Mar 2022 12:46:12 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1647863172; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MSx72V2HVU0T6x8Ncw4K7usjjkuwRvg2WkOZN5WtPJ0=; b=CEBozyWuRUie8ZKxpYfIvNQHo0IhGpO9L+9zh48kIO4VJAztR87wLxiTpDDadvTIZXz+Gr 5YYTfnJ/5ErPRtGO40ZsYJu6Syufl48HluQFtQ48ylI9KT6M4a+PCpy92syuSpsDY1+7Ut 0U9KUaEQy0gxPZXGw2fgazL6kDpebn0= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 21 Mar 2022 12:46:12 +0100 From: Michael Walle To: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Clause 45 and Clause 22 PHYs on one MDIO bus In-Reply-To: <240354b0a54b37e8b5764773711b8aa3@walle.cc> References: <240354b0a54b37e8b5764773711b8aa3@walle.cc> User-Agent: Roundcube Webmail/1.4.13 Message-ID: X-Sender: michael@walle.cc Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 2022-03-21 12:21, schrieb Michael Walle: > Hi, > > I have a board with a c22 phy (microchip lan8814) and a c45 phy > (intel/maxlinear gyp215) on one bus. If I understand it correctly, both > accesses should be able to coexist on one bus. But the microchip > lan8814 > actually has a bug and gets confused by c45 accesses. For example it > will > respond in the middle of another transaction with its own data if it > decodes it as a read. That is something we can see on a logic analyzer. > But we also see random register writes on the lan8814 (which you don't > see > on the logic analyzer obviously). Fortunately, the GPY215 supports > indirect > MMD access by the standard c22 registers. Thus as a workaround for the > problem, we could have a c22 only mdio bus. > > The SoC I'm using is the LAN9668, which uses the mdio-mscc-mdio driver. > First problem there, it doesn't support C45 (yet) but also doesn't > check > for MII_ADDR_C45 and happily reads/writes bogus registers. > > I've looked at the mdio subsystem in linux, there is probe_capabilities > (MDIOBUS_C45 and friends) but the mxl-gpy.c is using c45 accesses > nevertheless. I'm not sure if this is a bug or not. > > I was thinking of a fallback mechanism for the c45 read access like > in read_mmd. And even if the mdio controller is c45 capable, a PHY > might opt out. In my case, the lan8814. Actually, it looks like mdiobus_c45_read() is really c45 only and only used for PHYs which just support c45 and not c45-over-c22 (?). I was mistaken by the heavy use of the function in phy_device.c. All the methods in phy-c45.c use phy_*_mmd() functions. Thus it might only be the mxl-gpy doing something fishy in its probe function. (And I'm unsure about get_phy_c45_ids()). Nevertheless, I'd still need the opt-out of any c45 access. Otherwise, if someone will ever implement c45 support for the mdio-mscc-mdio driver, I'll run in the erratic behavior. -michael