From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Sun, 22 Nov 2009 08:20:47 +1100 From: David Gibson To: Vinayak Kale Subject: Re: DTS for PowerPC 440 based board Message-ID: <20091121212047.GA29715@yookeroo> References: <5eb65910911211046q433072f1nd2a6eb955593a37a@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <5eb65910911211046q433072f1nd2a6eb955593a37a@mail.gmail.com> Cc: linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sun, Nov 22, 2009 at 12:16:59AM +0530, Vinayak Kale wrote: > Hi, > I am porting 2.6.31 for a PowerPC 440 core based board. I have couple of > queries. I would really appreciate if someone could answer since i couldn't > find info from other places. > > 1) Is it mandatory to create a DTS file? Roughly speaking, yes. You have to supply a device tree to the kernel somehow, so if the firmware doesn't supply one itself, you will need to create a DTS. > 2) If uboot passes BDInfo struct to kernel instead of DT blob, then in this > case does kernel creates FDT at run time? Not exactly. In this case the bootwrapper will be built with an FDT (compiled from a dts) built in. It will however tweak the FDT with information from the BDInfo before booting the kernel proper. > 3) I believe in case of DTS, the kernel picks up the h/w info from DTS blob > so we need not hardcode any register addresses etc inside kernel other than > in dts file. What happens in case of uboot passing just BDInfo struct. How > do we specify the register addresses etc? There's always a device tree which specifies register addresses. If the firmware only supplies a BDInfo, then the kernel wrapper must have a device tree built in. In practice that will always be built from a dts, though it doesn't have to be in theory. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson