From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F4225C4321E for ; Sun, 9 Sep 2018 11:07:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9E1E220857 for ; Sun, 9 Sep 2018 11:07:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9E1E220857 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726725AbeIIP47 (ORCPT ); Sun, 9 Sep 2018 11:56:59 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:46204 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726650AbeIIP47 (ORCPT ); Sun, 9 Sep 2018 11:56:59 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E94B018A; Sun, 9 Sep 2018 04:07:39 -0700 (PDT) Received: from iMac.local (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E41083F5BC; Sun, 9 Sep 2018 04:07:36 -0700 (PDT) Date: Sun, 9 Sep 2018 12:07:33 +0100 From: Catalin Marinas To: Scott Branden Cc: Grant Likely , Arnd Bergmann , Ard Biesheuvel , Will Deacon , Linux Kernel Mailing List , Leif Lindholm , Alexander Graf , bcm-kernel-feedback-list@broadcom.com, Olof Johansson , Linux ARM Subject: Re: [PATCH] arm64: defconfig: enable EFI_ARMSTUB_DTB_LOADER Message-ID: <20180909110732.GA63296@iMac.local> References: <1f8095f1-1f0c-0791-31c4-c7b986c4ce1f@broadcom.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 05, 2018 at 11:04:36AM -0700, Scott Branden wrote: > On 18-09-05 11:00 AM, Grant Likely wrote: > > On Wed, Sep 5, 2018 at 6:27 PM Scott Branden wrote: > > > On 18-09-05 02:40 AM, Ard Biesheuvel wrote: > > > > On 4 September 2018 at 19:19, Scott Branden wrote: > > > > > Rather than introduce EFI_ARMSTUB_DTB_LOADER, why not have > > > > > the efistub use CONFIG_OF to determine whether it supports dtb= or not? > > > > > > > > > > That way ACPI-only distros disable devicetree support entirely. > > > > > > > > > Unfortunately, CONFIG_OF cannot be disabled on arm64 even on ACPI-only builds. > > > OF shouldn't be automatically selected in the arm64/Kconfig. It should > > > have a config parmaeter like other archs as mips and arm. I can > > > submit a patch so it functions the same way as other archs so it > > > is not always selected. It will be good to add a USE_OF config > > > options like the other archs (or simply remove the select from the > > > Kconfig and choose OF directly in the defconfig. This will have > > > the added benefit of doing away with OF support when its not > > > needed on an ARM64 platform. ACPI is already not automatically > > > selected for all ARM64 platforms, nor should devicetree. > > We don't do that on Arm because a devicetree is always required at > > boot time. Even on ACPI systems a tiny DTB is used containing just a > > /chosen node for passing the kernel command line and the initrd > > location. > > Seems bizarre DTB is not needed for x86 to boot from UEFI with ACPI > support?  I'll look into it further at some point in order to remove such > anomaly.  There should be no need for such devicetree reliance. I'd say don't waste time on this, the patch would not get merged ;). As Grant said, we use a tiny dtb to pass the command line, initrd to the kernel. You'd have to invent an alternative (setup_header, ATAGs) and I really don't see the point of increased complexity just because of some philosophical arguments against OF. -- Catalin