Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753510AbcCQQDO (ORCPT ); Thu, 17 Mar 2016 12:03:14 -0400 Received: from foss.arm.com ([217.140.101.70]:49181 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752685AbcCQQDM (ORCPT ); Thu, 17 Mar 2016 12:03:12 -0400 Subject: Re: [PATCH] Revert "arm64: Increase the max granular size" To: Catalin Marinas , Timur Tabi References: <1458120743-12145-1-git-send-email-opensource.ganesh@gmail.com> <20160316100759.GA18387@arm.com> <56E95A4E.4050709@codeaurora.org> <20160316141802.GC13423@e104818-lin.cambridge.arm.com> <56E97B10.4050401@codeaurora.org> <20160317142716.GC11623@e104818-lin.cambridge.arm.com> <56EAC40F.1080504@codeaurora.org> <20160317153747.GD11623@e104818-lin.cambridge.arm.com> Cc: Ganesh Mahendran , Will Deacon , linux-kernel@vger.kernel.org, stable@vger.kernel.org, rrichter@cavium.com, tchalamarla@cavium.com, Shanker Donthineni , apinski@cavium.com, linux-arm-kernel@lists.infradead.org From: Marc Zyngier X-Enigmail-Draft-Status: N1110 Organization: ARM Ltd Message-ID: <56EAD53C.80707@arm.com> Date: Thu, 17 Mar 2016 16:03:08 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.5.0 MIME-Version: 1.0 In-Reply-To: <20160317153747.GD11623@e104818-lin.cambridge.arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1414 Lines: 31 On 17/03/16 15:37, Catalin Marinas wrote: > On Thu, Mar 17, 2016 at 09:49:51AM -0500, Timur Tabi wrote: [...] >> Keep in mind that on an ACPI system like ours, the boot loader (UEFI in our >> case) configures the system extensively. It does a lot of things that the >> kernel would normally do on a device tree system. For example, pin control >> is handled completely by UEFI. The kernel does not set the pin muxes or >> GPIO directions. That means we don't support dynamic pin muxing. Before >> the kernel is booted, the GPIO pins are fixed. > > And that's great. But you are mistaken in thinking that DT requires lots > of drivers in the kernel and prevents the firmware from doing sane > stuff. DT rather gained additional features out of necessity since the > firmware was not always doing a proper job at hardware initialisation. > A DT-enabled kernel does not impose restrictions on such firmware > features. With ACPI, the choice is not as wide and forces vendors to > look into their firmware story from a different angle (until they figure > the _DSD+PRP0001 out and we end up with DT emulated in ACPI). Or even worse, perverting the couple of things that were actually OK in ACPI by inventing a new layer of broken stuff: http://thread.gmane.org/gmane.linux.ports.arm.msm/17828 Once we've reached that level, _DSD fells all nice and cuddly. M. -- Jazz is not dead. It just smells funny...