From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752359AbcFBHYf (ORCPT ); Thu, 2 Jun 2016 03:24:35 -0400 Received: from mout.kundenserver.de ([212.227.126.187]:53992 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751916AbcFBHYe (ORCPT ); Thu, 2 Jun 2016 03:24:34 -0400 From: Arnd Bergmann To: linux-arm-kernel@lists.infradead.org Cc: Gerd Hoffmann , 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 Subject: Re: [PATCH 09/32] bcm2837-rpi-3-b.dts for 32bit arm Date: Thu, 02 Jun 2016 09:24:25 +0200 Message-ID: <3336185.FIBLI6ezsy@wuerfel> User-Agent: KMail/5.1.3 (Linux/4.4.0-22-generic; KDE/5.18.0; x86_64; ; ) In-Reply-To: <1464850565.24775.40.camel@redhat.com> References: <1464817421-8519-1-git-send-email-kraxel@redhat.com> <5616246.RRQ2rLjLud@wuerfel> <1464850565.24775.40.camel@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:7gY/UQr6BmJo0l/b0265PCFXmJKIVv1hFmY3E+TC1PyKMZxLU5b LV1599zR1+9vXFNR77TOZiQLyTGT8M4Epksh8Tjkb71IvUIHvxCPmo9b5NIE47pGTqlQVGq Li7Yf2L5hR25sDkFK/z9jezjyXCkfxH0mJZL0hA5L3XxZ9DaADSouYlsMGZWRXLNqaA/dFs WRdEPKpJ8PdONItcSNIsA== X-UI-Out-Filterresults: notjunk:1;V01:K0:EyZXI049oFU=:vfY+cth7pXSWZdystKmtHP TvCOih/PifcJTlZ3/sqZdJlhACWtjYzbX4f5zwcoqhuNyG7PhNnnYaOv5zCD4eiwYVS2goefh Eh+vW1m8HAiFn2LUp0Zn6SWa0+TkD/ygJJOKv88W1K/tea1+rCrgm8OiG0MLwxStpat85aQL+ zxalpQuYvhLGy6Q3SEZRQ6CFoB8Vk5Rg9zwkYe25f2fBtVjXgfLe/CpT+z7DHPYNjhrb1A7cf 5YviA9N3/LGUD0fmhQ11zCFfBn8p/BqfuBzzmGJEPV6JV9YJbjBkniQenrQnKsnAm5hbktbDm grlTM0EOZXfbk1mcE/RSRhbqPEVF6+wGdh6UwgtrA7hwz0NqvHfNP6EotEQEmkxxvmJ+CWTC6 qvKjbs5Mj2FEMNc7ZFE5kwyYy5FYqca3UlQ1j2yi/VuiALY/PhJ48yCe1X/e2u20cBZ7LRFj9 O8Ml4kXZQGblm6yUIvPi+UpLa0GylpuNnCjehJi9+CphnQhHPZXN+um51r+DJ5XzojdBrdpkD GTO7re2WmR/Ui/Q51xY5pgUTXCAF1mkEs6HSXQGHfogI7KOOJfW88fBKKKzWJi9mDvZIJd+Gu yJb3QECnRySb5F5zIKYDzC1xUN35l6w7qqmZIxBYFqp0poIM9vm68o3gmuL0C3IvcYZOdgTQz 51+3HgtU4aX2pyBucihzCrWMjd3HodAVUBNmfNZjjuamDhEgFFK3Ywvmt7qdd7J8kuu7PwQTV G59AdPwk41q6gUEQ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday, June 2, 2016 8:56:05 AM CEST Gerd Hoffmann wrote: > On Do, 2016-06-02 at 00:39 +0200, Arnd Bergmann wrote: > > On Wednesday, June 1, 2016 3:30:35 PM CEST Eric Anholt wrote: > > > Arnd Bergmann writes: > > > > > > > On Wednesday, June 1, 2016 11:43:18 PM CEST Gerd Hoffmann wrote: > > > >> diff --git a/arch/arm/boot/dts/bcm2837-rpi-3-b.dts b/arch/arm/boot/dts/bcm2837-rpi-3-b.dts > > > >> new file mode 100644 > > > >> index 0000000..36178a6 > > > >> --- /dev/null > > > >> +++ b/arch/arm/boot/dts/bcm2837-rpi-3-b.dts > > > >> @@ -0,0 +1 @@ > > > >> +#include "../../../arm64/boot/dts/broadcom/bcm2837-rpi-3-b.dts" > > > >> -- > > > >> 1.8.3.1 > > > >> > > > > > > > > What does this gain you? > > > > > > Many Raspberry Pi users use a small set of SD cards that they swap > > > between various versions of the hardware. It would be good to have > > > their 32-bit OS images work on the Pi3 as well. > > > > Sure, but you already have the dts file in the other directory, > > and the dtb is the same. > > > > According to the comment in the other patch, the idea was to have > > the file in the arm64 directory because it's a 64-bit platform, > > but now you have it here as well. > > 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. - 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. 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. Arnd