From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Herring Subject: Re: [PATCH v2 1/4] devicetree: bindings: Properly document micrel ks8851 SPI chips Date: Wed, 28 May 2014 11:38:48 -0500 Message-ID: References: <1400875040-13269-1-git-send-email-sboyd@codeaurora.org> <1400875040-13269-2-git-send-email-sboyd@codeaurora.org> <20140524124858.GR22111@sirena.org.uk> <5385063F.30407@codeaurora.org> <20140528151646.GU20155@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20140528151646.GU20155@pengutronix.de> Sender: linux-kernel-owner@vger.kernel.org To: =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= Cc: Stephen Boyd , Mark Brown , "David S . Miller" , Nishanth Menon , Mark Rutland , Pawel Moll , Ian Campbell , linux-arm-msm , Kumar Gala , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , Rob Herring , netdev , "linux-arm-kernel@lists.infradead.org" List-Id: devicetree@vger.kernel.org On Wed, May 28, 2014 at 10:16 AM, Uwe Kleine-K=C3=B6nig wrote: > Hello Stephen, > > On Tue, May 27, 2014 at 02:40:15PM -0700, Stephen Boyd wrote: >> On 05/24/14 05:48, Mark Brown wrote: >> > On Fri, May 23, 2014 at 12:57:17PM -0700, Stephen Boyd wrote: >> > >> >> Optional properties: >> >> -- vdd-supply: supply for Ethernet mac >> >> +- vdd-supply: analog 3.3V supply for Ethernet mac >> >> +- vdd-io-supply: digital 1.8V IO supply for Ethernet mac >> > So, according to the datasheet I managed to find this device has a >> > supply VDD_IO (so normally written vdd-io-supply here), some other >> > supplies which are tied to VDD_IO (so can probably be omitted) and= a >> > supply VDD_A3.3 none of which are optional. There is an internal >> > regulator which can be used to drop a higher voltage VDD_IO down f= or >> > some of the supplies tied to it but that's essentially a noop from >> > software as far as I can tell. None of these supplies are obvious= ly >> > optional, though I've not read the datasheet in detail so I may ha= ve >> > missed something here. > There is a difference between the supply being optional for the hardw= are > to work and the need to specify it in the device tree, isn't it? My > expectation is that when it's not specified there is just nothing the > the software needs to care for. Yes, agreed. Of course you could have cases where a supply at the h/w level is optional like if a supply can be powered externally or via an internal regulator. Those cases will have to be made clear in the binding, but a heading "Optional properties" in a binding doc means properties which are optional to specify in DT. Rob