From mboxrd@z Thu Jan 1 00:00:00 1970 From: hanjun.guo@linaro.org (Hanjun Guo) Date: Tue, 06 Jan 2015 21:50:38 +0800 Subject: [PATCH v5 18/18] Documentation: ACPI for ARM64 In-Reply-To: <20150106112929.GB8829@e104818-lin.cambridge.arm.com> References: <1413553034-20956-1-git-send-email-hanjun.guo@linaro.org> <1413553034-20956-19-git-send-email-hanjun.guo@linaro.org> <20141224171815.GD13399@e104818-lin.cambridge.arm.com> <54A90A4C.60908@linaro.org> <20150105110533.GA14967@e104818-lin.cambridge.arm.com> <54ABC2CB.6@linaro.org> <20150106112929.GB8829@e104818-lin.cambridge.arm.com> Message-ID: <54ABE82E.30308@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 2015?01?06? 19:29, Catalin Marinas wrote: > On Tue, Jan 06, 2015 at 11:11:07AM +0000, Hanjun Guo wrote: >> On 2015?01?05? 19:05, Catalin Marinas wrote: >>> On Sun, Jan 04, 2015 at 09:39:24AM +0000, Hanjun Guo wrote: >>>> On 2014?12?25? 01:18, Catalin Marinas wrote: >>>> [...] >>>>> >>>>> In addition to the above and _DSD requirements/banning, I would also add >>>>> some clear statements around: >>>>> >>>>> _OSC: only global/published capabilities are allowed. For >>>>> device-specific _OSC we need a process or maybe we can ban them entirely >>>>> and rely on _DSD once we clarify the process. >>>>> >>>>> _OSI: firmware must not check for certain _OSI strings. Here I'm not >>>>> sure what we would have to do for ARM Linux. Reporting "Windows" does >>>>> not make any sense but not reporting anything can, as Matthew Garrett >>>>> pointed out, can be interpreted by firmware as "Linux". In addition to >>>>> any statements in this document, I suggest you patch >>>>> drivers/acpi/acpica/utosi.c accordingly, maybe report "Linux" for ARM >>>>> and print a kernel warning so that we notice earlier. >>>>> >>>>> ACPI_OS_NAME: this is globally defined as "Microsoft Windows NT". It >>>>> doesn't make much sense in the ARM context. Could we change it to >>>>> "Linux" when CONFIG_ARM64? >> >> I think we can introduce a Kconfig such as CONFIG_ACPI_OS_NAME_LINUX, >> selected by ARM64 and change ACPI_OS_NAME to "Linux" when >> CONFIG_ACPI_OS_NAME_LINUX defined. (we can not add CONFIG_ARM64 in >> ACPICA code directly since it will be used by windows too) >> >> some code like below: > > This looks fine for me (with some minor comments below) but I'm not an > ACPI expert to say there wouldn't be any issues. > >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index b1f9a20..de567a3 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -1,5 +1,6 @@ >> config ARM64 >> def_bool y >> + select ACPI_OS_NAME_LINUX if ACPI >> select ARCH_BINFMT_ELF_RANDOMIZE_PIE >> select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE >> select ARCH_HAS_GCOV_PROFILE_ALL >> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig >> index 8951cef..11a10ac 100644 >> --- a/drivers/acpi/Kconfig >> +++ b/drivers/acpi/Kconfig >> @@ -369,6 +369,10 @@ config ACPI_REDUCED_HARDWARE_ONLY >> >> If you are unsure what to do, do not enable this option. >> >> +config ACPI_OS_NAME_LINUX >> + bool "Using Linux for _OS method" if EXPERT >> + def_bool n > > No need for a default n, it is off by default. Alternatively you could > say: > > default y if ARM64 ok. > >> + >> source "drivers/acpi/apei/Kconfig" >> >> config ACPI_EXTLOG >> diff --git a/include/acpi/acconfig.h b/include/acpi/acconfig.h >> index 5a0a3e5..db5e13e 100644 >> --- a/include/acpi/acconfig.h >> +++ b/include/acpi/acconfig.h >> @@ -69,7 +69,11 @@ >> * code that will not execute the _OSI method unless _OS matches the >> string >> * below. Therefore, change this string at your own risk. >> */ >> +#ifndef ACPI_OS_NAME_USING_LINUX >> #define ACPI_OS_NAME "Microsoft Windows NT" >> +#else >> +#define ACPI_OS_NAME "Linux" >> +#endif > > Can you not use CONFIG_ACPI_OS_NAME_LINUX directly here without > introducing another macro? acconfig.h is part of ACPICA core and will be shared by windows and other OS, so use CONFIG from Linux in this file is not allowed I think. > >>>> We will work on this both on ASWG and linux ACPI driver side, as Dong >>>> and Charles pointed out, _OSI things can be solved in ACPI spec, when >>>> that is done, we can modify the kernel driver to fix the problems above. >>> >>> Which driver? >> >> the ACPICA core driver as you suggested, sorry for the confusion. >> >>> What about ACPI_OS_NAME? Would you suggest it is fine to report >>> "Microsoft Windows NT" on an ARM system? That _OS_ not _OSI. >> >> No, not at all. I prefer "Linux" >> In include/acpi/acconfig.h, when ACPI_OS_NAME defined, it says: >> "OS name, used for the _OS object. The _OS object is essentially >> obsolete,..." >> for some legacy reasons, we needed "Microsoft Windows NT", but ACPI >> for ARM64 on linux is totally new, I think we can change it to >> "Linux" when CONFIG_ARM64 as you suggested. > > We could ignore this change for now if we don't expect the _OS object to > be used at all. But do we have any other way to check the AML code for > this? Would FWTS catch such obsolete cases? I'm not sure, I will check it and get back when I have the answer. Thanks Hanjun