[PATCH v9 18/21] ARM64 / ACPI: Select ACPI_REDUCED_HARDWARE_ONLY if ACPI is enabled on ARM64

[Lorenzo Pieralisi]

On Wed, Feb 25, 2015 at 08:39:58AM +0000, Hanjun Guo wrote:
> From: Al Stone <al.stone at linaro.org>
> 
> ACPI reduced hardware mode is disabled by default, but ARM64
> can only run properly in ACPI hardware reduced mode, so select
> ACPI_REDUCED_HARDWARE_ONLY if ACPI is enabled on ARM64.

Agreed. This will remove unneeded acpica code. I think though,
you should also check the FADT flag HW_REDUCED_ACPI at boot to
make sure that the tables are HW reduced compliant. I am flagging
this up because I noticed code in core code (not guarded by
ifdef) that checks:

acpi_gbl_reduced_hardware

and if it is not set it goes on instantiating fixed HW devices.

drivers/acpi/scan.c:2567

It is just a heads up, I think it is harmless, but one thing is
removing acpica code on ACPI HW reduced only, the other is to make
sure the kernel does not try to use ACPI HW features that acpica
can't support.

Lorenzo

> CC: Catalin Marinas <catalin.marinas at arm.com>
> CC: Will Deacon <will.deacon at arm.com>
> Reviewed-by: Grant Likely <grant.likely at linaro.org>
> Tested-by: Suravee Suthikulpanit <Suravee.Suthikulpanit at amd.com>
> Tested-by: Yijing Wang <wangyijing at huawei.com>
> Tested-by: Mark Langsdorf <mlangsdo at redhat.com>
> Tested-by: Jon Masters <jcm at redhat.com>
> Tested-by: Timur Tabi <timur at codeaurora.org>
> Tested-by: Robert Richter <rrichter at cavium.com>
> Acked-by: Robert Richter <rrichter at cavium.com>
> Signed-off-by: Al Stone <al.stone at linaro.org>
> Signed-off-by: Hanjun Guo <hanjun.guo at linaro.org>
> ---
>  arch/arm64/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 1b8e973..d00ab9a 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1,5 +1,6 @@
>  config ARM64
>  	def_bool y
> +	select ACPI_REDUCED_HARDWARE_ONLY if ACPI
>  	select ARCH_BINFMT_ELF_RANDOMIZE_PIE
>  	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
>  	select ARCH_HAS_GCOV_PROFILE_ALL
> -- 
> 1.9.1
> 
>