From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Sun, 9 Sep 2018 12:07:33 +0100 Subject: [PATCH] arm64: defconfig: enable EFI_ARMSTUB_DTB_LOADER In-Reply-To: References: <1f8095f1-1f0c-0791-31c4-c7b986c4ce1f@broadcom.com> Message-ID: <20180909110732.GA63296@iMac.local> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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