From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 7 Sep 2007 11:15:53 +1000 From: David Gibson To: Scott Wood Subject: Re: [PATCH v7 3/3] [POWERPC] MPC832x_RDB: update dts to use SPI1in QE, register mmc_spi stub Message-ID: <20070907011553.GO26079@localhost.localdomain> References: <46D73166.6080103@freescale.com> <989B956029373F45A0B8AF02970818900147BD4D@zch01exm26.fsl.freescale.net> <46DC126C.9060603@freescale.com> <20070903151319.GA24840@localhost.localdomain> <20070904104750.GA32451@localhost.localdomain> <20070904182028.GC18280@ld0162-tx32.am.freescale.net> <20070905114023.GA4072@localhost.localdomain> <20070905132106.GB24637@ld0162-tx32.am.freescale.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20070905132106.GB24637@ld0162-tx32.am.freescale.net> Cc: linuxppc-dev@ozlabs.org, Timur Tabi List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Sep 05, 2007 at 08:21:06AM -0500, Scott Wood wrote: > On Wed, Sep 05, 2007 at 03:40:23PM +0400, Anton Vorontsov wrote: > > On Tue, Sep 04, 2007 at 01:20:28PM -0500, Scott Wood wrote: > > > The kernel is of course welcome to do so -- and this may be a valid > > > reason to attach pin information to specific device nodes, if it actually > > > saves a non-negligible amount of power -- but it's not a reason to force > > > the kernel to have to care by not setting things up in the firmware. > > > > Well, I might agree here. But to me it seems unnatural that I have to > > upgrade bootloader to use SPI -- I can already boot the kernel. > > Sure -- the firmware should have been done right the first time. > > Unfortunately, it very often doesn't, and thus fixups in the kernel's > platform code are warranted, but the firmware is still the preferred > place to do it. Appealing though it is, I think the whole "firmware is the preferred place to do it" approach is a lost cause (for nearly every value of "it"). Firmwares are, more often than not, crap, and that's unlikely to change. For a lot of things, having the kernel or bootwrapper cope as a special case with a handful of crap firmwares which don't set things up properly isn't actually any easier than having it set them up itself, always. Which is why I err strongly in favour of having the kernel set things up rather than rely on firmware setup, unless there's a very strong reason why we *have* to respect the firmware's setup. (Incidentally, this reasoning is why although the approach is very neat-looking, I'm actually quite uncomfortable with firmwares directly supplying flattened device trees to the kernel, rather than having the tree in the bootwrapper.) -- 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