From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Stone Subject: Re: [PATCH v5 1/5] ACPI: introduce CONFIG_ACPI_REDUCED_HARDWARE_ONLY to enforce this ACPI mode Date: Thu, 09 Jan 2014 14:20:23 -0700 Message-ID: <52CF1297.9030306@redhat.com> References: <1389142011-27356-1-git-send-email-al.stone@linaro.org> <1389142011-27356-2-git-send-email-al.stone@linaro.org> <201401081346.25767.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:13758 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756190AbaAIVVC (ORCPT ); Thu, 9 Jan 2014 16:21:02 -0500 In-Reply-To: Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Catalin Marinas , Arnd Bergmann Cc: linaro-kernel , al.stone@linaro.org, "patches@linaro.org" , linaro-acpi@lists.linaro.org, linux-acpi@vger.kernel.org, Hanjun Guo , "linux-arm-kernel@lists.infradead.org" On 01/09/2014 10:38 AM, Catalin Marinas wrote: > On 8 January 2014 12:46, Arnd Bergmann wrote: >> On Wednesday 08 January 2014, al.stone@linaro.org wrote: >>> Even though support for X86 in hardware reduced mode is possible, it >>> is NOT enabled. Extensive effort has gone into the Linux kernel so that >>> there is a single kernel image than can run on all x86 hardware; the kernel >>> changes run-time behavior to adapt to the hardware being used. This is not >>> currently possible with the existing ACPICA infrastructure but only presents >>> a problem on achitectures supporting both hardware-reduced and legacy modes >>> of ACPI -- i.e., on x86 only. >> >> Not sure about the logic here: While it's certainly possible to build a kernel >> that runs on all x86 machines, it's also possible to build one that only >> runs on some of them when some basic options are turned off. I don't see >> any difference between that and what we have on ARM64 or the multiplatform >> subset of ARM32. > > Would we ever need !CONFIG_ACPI_REDUCED_HARDWARE_ONLY on ARM or ARM64? > If not, we could even make this always on for these archs. > Not that I know of -- and I would hope not. This mode is so much more straightforward that it makes no sense to me to do anything but reduced HW if you have the choice. I assume you were thinking of something like this in the arch Kconfig file: config ARM64 .... select ACPI_REDUCED_HARDWARE_ONLY if ACPI ... But, do let me know if you had something else in mind. I think it does make sense to add so I'll put this in the next version. -- ciao, al ----------------------------------- Al Stone Software Engineer Red Hat, Inc. ahs3@redhat.com -----------------------------------