Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755579AbdIHORs (ORCPT ); Fri, 8 Sep 2017 10:17:48 -0400 Received: from vps0.lunn.ch ([178.209.37.122]:33076 "EHLO vps0.lunn.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753243AbdIHORq (ORCPT ); Fri, 8 Sep 2017 10:17:46 -0400 Date: Fri, 8 Sep 2017 16:17:36 +0200 From: Andrew Lunn To: Corentin Labbe Cc: robh+dt@kernel.org, mark.rutland@arm.com, maxime.ripard@free-electrons.com, wens@csie.org, linux@armlinux.org.uk, catalin.marinas@arm.com, will.deacon@arm.com, peppe.cavallaro@st.com, alexandre.torgue@st.com, f.fainelli@gmail.com, netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 10/10] net: stmmac: dwmac-sun8i: Handle integrated/external MDIOs Message-ID: <20170908141736.GF25219@lunn.ch> References: <20170908071156.5115-1-clabbe.montjoie@gmail.com> <20170908071156.5115-11-clabbe.montjoie@gmail.com> <20170908130520.GA11248@lunn.ch> <20170908132632.GA3037@Red> <20170908140020.GC25219@lunn.ch> <20170908140832.GB3037@Red> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170908140832.GB3037@Red> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 461 Lines: 12 > > Do you know why the reset times out/fails? > > > > Because there are nothing connected to it. That should not be an issue. A read should just return 0xffff. And it should return 0xffff fast. The timing of the MDIO protocol is fixed. A read or a write takes a fixed number of cycles, independent of if there is a device there or not. The bus data line has a pullup, so if you try to access a missing device, you automatically read 0xffff. Andrew