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: Fri, 10 Jan 2014 10:12:32 -0700 Message-ID: <52D02A00.3000209@linaro.org> 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> <52CF1297.9030306@redhat.com> <20140110103757.GC925@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pa0-f49.google.com ([209.85.220.49]:60170 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751620AbaAJRMe (ORCPT ); Fri, 10 Jan 2014 12:12:34 -0500 Received: by mail-pa0-f49.google.com with SMTP id bj1so1181378pad.36 for ; Fri, 10 Jan 2014 09:12:34 -0800 (PST) In-Reply-To: <20140110103757.GC925@arm.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Catalin Marinas , Al Stone Cc: Arnd Bergmann , linaro-kernel , "patches@linaro.org" , "linaro-acpi@lists.linaro.org" , "linux-acpi@vger.kernel.org" , Hanjun Guo , "linux-arm-kernel@lists.infradead.org" On 01/10/2014 03:37 AM, Catalin Marinas wrote: > On Thu, Jan 09, 2014 at 09:20:23PM +0000, Al Stone wrote: >> 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. > > Thanks for clarifying. > >> 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. > > The change makes sense but I think it should come with the patches for > ACPI support on arm64 rather than your hw-reduced patches. > Ah. Indeed. That makes more sense; I'll pass it on to my colleagues. -- ciao, al ----------------------------------- Al Stone Software Engineer Linaro Enterprise Group al.stone@linaro.org -----------------------------------