From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1161233AbcFBPPu (ORCPT <rfc822;w@1wt.eu>);
	Thu, 2 Jun 2016 11:15:50 -0400
Received: from mx1.redhat.com ([209.132.183.28]:47238 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1161167AbcFBPPs convert rfc822-to-8bit (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 2 Jun 2016 11:15:48 -0400
Message-ID: <1464880291.24775.111.camel@redhat.com>
Subject: Re: [PATCH 09/32] bcm2837-rpi-3-b.dts for 32bit arm
From: Gerd Hoffmann <kraxel@redhat.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arm-kernel@lists.infradead.org, Mark Rutland <mark.rutland@arm.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
        Pawel Moll <pawel.moll@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        Russell King <linux@armlinux.org.uk>,
        open list <linux-kernel@vger.kernel.org>,
        Eric Anholt <eric@anholt.net>, Rob Herring <robh+dt@kernel.org>,
        linux-rpi-kernel@lists.infradead.org,
        Kumar Gala <galak@codeaurora.org>
Date: Thu, 02 Jun 2016 17:11:31 +0200
In-Reply-To: <4795604.XAe8xnhung@wuerfel>
References: <1464817421-8519-1-git-send-email-kraxel@redhat.com>
	 <3336185.FIBLI6ezsy@wuerfel> <1464858870.24775.65.camel@redhat.com>
	 <4795604.XAe8xnhung@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 [10.5.110.28]); Thu, 02 Jun 2016 15:15:47 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

  Hi,

> > > > Reference to ../../../arm64/boot/dts/broadcom/bcm2837-rpi-3-b.dts
> > > > directly in the Makefile?

Actually tried that, and to my surprise this worked fine for both "make
dtbs" and "make dtbs_install".

So we should just do that I guess ...

> > 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.
> 
> I think the Allwinner A64 and the Samsung s5p6818 are other examples
> for this, where the initial run of boards all run 32-bit kernels
> for much of the same reasons. If users want to run a 32-bit distro
> on rpi-3 and on e.g. orange-pi, I don't see why they wouldn't also run
> the same binary on A64.

... and others can join the party on a case-by-case basis.

I still expect for the majority of arm64 boards it is not very useful,
so I don't think we should build all of them unconditionally.

cheers,
  Gerd