From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Fri, 10 Jan 2014 10:37:58 +0000 Subject: [PATCH v5 1/5] ACPI: introduce CONFIG_ACPI_REDUCED_HARDWARE_ONLY to enforce this ACPI mode In-Reply-To: <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> <52CF1297.9030306@redhat.com> Message-ID: <20140110103757.GC925@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 at 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. -- Catalin