From mboxrd@z Thu Jan 1 00:00:00 1970 From: andrew@lunn.ch (Andrew Lunn) Date: Fri, 8 Sep 2017 16:17:36 +0200 Subject: [PATCH v5 10/10] net: stmmac: dwmac-sun8i: Handle integrated/external MDIOs In-Reply-To: <20170908140832.GB3037@Red> 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> Message-ID: <20170908141736.GF25219@lunn.ch> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org > > 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 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Lunn Subject: Re: [PATCH v5 10/10] net: stmmac: dwmac-sun8i: Handle integrated/external MDIOs Date: Fri, 8 Sep 2017 16:17:36 +0200 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 Return-path: Content-Disposition: inline In-Reply-To: <20170908140832.GB3037@Red> Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: devicetree@vger.kernel.org > > 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