From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752895AbcFBJOf (ORCPT ); Thu, 2 Jun 2016 05:14:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35030 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751317AbcFBJOd convert rfc822-to-8bit (ORCPT ); Thu, 2 Jun 2016 05:14:33 -0400 Message-ID: <1464858870.24775.65.camel@redhat.com> Subject: Re: [PATCH 09/32] bcm2837-rpi-3-b.dts for 32bit arm From: Gerd Hoffmann To: Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, Mark Rutland , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Pawel Moll , Ian Campbell , Russell King , open list , Eric Anholt , Rob Herring , linux-rpi-kernel@lists.infradead.org, Kumar Gala Date: Thu, 02 Jun 2016 11:14:30 +0200 In-Reply-To: <3336185.FIBLI6ezsy@wuerfel> References: <1464817421-8519-1-git-send-email-kraxel@redhat.com> <5616246.RRQ2rLjLud@wuerfel> <1464850565.24775.40.camel@redhat.com> <3336185.FIBLI6ezsy@wuerfel> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Mime-Version: 1.0 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Thu, 02 Jun 2016 09:14:32 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, > > Well, it just includes the arm64 version as-is, so we don't have > > duplication. I'm open to suggestions to how handle this better. > > > > Symbolic link? > > > > Reference to ../../../arm64/boot/dts/broadcom/bcm2837-rpi-3-b.dts > > directly in the Makefile? > > > > I've seen arch/arm/boot/dts/Makefile uses globs on *.dts, so I suspect > > the later wouldn't be that straight forward. > > It's just weird that the arm64 file includes the .dtsi files from arch/arm/ > and is then again included back from another file there. > > I can see two possible ways to handle this better: > > - leave the complete set of bcm2837 files in arch/arm and then have one > reference from arch/arm64 per .dts that refers to just that file. So basically do it the other way around. Would be a bit less messy indeed. > - come up with a rule to also build the .dtb files in arch/arm64 when > we run 'make dtbs' for arch/arm and leave this file there. The argument > that one could use the same dtb with a 32-bit kernel should basically > hold true for any arm64 system, it's not specific to rpi-3 really. Yes, in theory. No, in practice. As far I know the rpi3 is the only 64bit soc where a almost identical 32bit version exists, so running 32bit kernels on a 64bit processor actually happens in practice and I expect this to continue. If you want create sdcard images which run on any rpi variant this is pretty much the only reasonable way to do it. > We don't normally test 32-bit kernels on 64-bit SoCs because 64-bit > kernels are more efficient in a number of ways, and I'm sure there > are bugs that prevent some systems from working (aside from how some > machines cannot work because they don't have RAM below 4GB), but if > this is now something that users are interested in, making it just > work seems nicer than having a couple of board specific hacks. See above, I have my doubts that the user interest in this expands to other boards. So I'd tend to pick the first option. cheers, Gerd