From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Boyd Subject: Re: [PATCH v2 1/4] devicetree: bindings: Properly document micrel ks8851 SPI chips Date: Wed, 28 May 2014 12:44:35 -0700 Message-ID: <53863CA3.7040000@codeaurora.org> 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> <20140528171219.GD5099@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: =?ISO-8859-1?Q?Uwe_Kleine-K=F6nig?= , "David S . Miller" , Nishanth Menon , Mark Rutland , Pawel Moll , Ian Campbell , linux-arm-msm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Kumar Gala , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Rob Herring , netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org To: Mark Brown Return-path: In-Reply-To: <20140528171219.GD5099-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org On 05/28/14 10:12, Mark Brown wrote: > On Wed, May 28, 2014 at 05:16:46PM +0200, Uwe Kleine-K=F6nig wrote: >> On Tue, May 27, 2014 at 02:40:15PM -0700, Stephen Boyd wrote: >>> On 05/24/14 05:48, Mark Brown wrote: >>>> 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 hard= ware >> 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 th= e >> the software needs to care for.=20 > If the supply must always be physically present the bindings should b= e > specified as it being mandatory and the code written in that fashion;= as > an extension Linux will put a dummy in but this is attempting to hand= le > incorrect DTs. This means we have functional error handling in cases > where there is something to worry about and simplifies the code using > the regulator. Ok, you're saying the opposite of Rob. Should it be required or optiona= l in the DT binding? > > regulator_get_optional() should *only* be used if the supply may be > omitted from the physical design and should generally always be > accompanied by code which does something substantially different such= as > using an internal regulator or changing the source for a reference > voltage instead. > > Ok. Dave M has already picked up all these patches so I'll send a patch to replace regulator_get_optional() with regulator_get() and fix up the error handling unless I hear otherwise. --=20 Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html