From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from nz-out-0506.google.com (nz-out-0506.google.com [64.233.162.239]) by ozlabs.org (Postfix) with ESMTP id 17D8CDDE36 for ; Thu, 16 Aug 2007 00:04:02 +1000 (EST) Received: by nz-out-0506.google.com with SMTP id l1so771908nzf for ; Wed, 15 Aug 2007 07:04:01 -0700 (PDT) Message-ID: Date: Wed, 15 Aug 2007 08:03:57 -0600 From: "Grant Likely" Sender: glikely@secretlab.ca To: "Stephen Neuendorffer" Subject: Re: Device Tree tool [was RE: [PATCH] Consolidate XILINX_VIRTEXboardsupport] In-Reply-To: <20070814215438.3C7AA1B7006C@mail148-cpk.bigfish.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 References: <20070810153619.0471D190055@mail15-fra.bigfish.com> <20070814215438.3C7AA1B7006C@mail148-cpk.bigfish.com> Cc: microblaze-uclinux@itee.uq.edu.au, linuxppc-embedded@ozlabs.org List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 8/14/07, Stephen Neuendorffer wrote: > > > BTW: I'm currently hacking away to see if I can get a > > microblaze system > > booting > > using a flat device tree... I haven't decided if it's worth it to go > > that > > route in the end yet, but... > > > > Steve > > I've managed to get the first step working: a microblaze system > advertising of_devices in 2.6 using a flat device tree. The next task > is to > reimplement probe() for a driver or two (probably the xilinx_emac driver > first). My plan is to have the driver advertise both through > of_platform_bus, and > through the regular platform bus, and have a config option that either > advertises > the devices through of and links in the device tree, or using the > exising > platform_device mechanism. That's fantastic. Yes, I think that is the right approach to have both platform_bus and of_platform bus bindings in the drivers. > > Grant: Does this make sense (in terms of dealing with drivers) with > your plans for > moving Virtex platforms to arch/powerpc? I'd like to avoid duplicating > work on the > drivers, if possible. Absolutely > > Is there a concensus on how microblaze systems should get booted? > Currently, > I'm linking the device tree directly into the kernel itself, loading the > whole > mess using SystemAce and the start address jumps directly into the > kernel, which > is quite a bit different than the way powerpc works. It's certainly > simpler: > maybe too simple. At the same time, replicating > the complexity of arch/powerpc with separate boot code may or may not be > worth it... > Any thoughts? It is a good starting point, and I think it is important that this remain an option (ie. for boards without a bootloader). However, it is a really good idea to support the notion of passing in a device tree from a bootloader (u-boot). As Michal mentioned, u-boot already has the code to support this, and u-boot is able to update the device tree directly. The key feature here is being able to support multiple FPGA designs from a single kernel image because the device tree gives us some level of abstraction on the hardware design. Cheers, g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. grant.likely@secretlab.ca (403) 399-0195