Subject: Re: [PATCH] powerpc: Restrict ARCH_HIBERNATION_POSSIBLE to supported configurations

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 15 Nov 2023 13:39:54 +0530

Vishal Chourasia <[email-masked]> writes:

> This patch modifies the ARCH_HIBERNATION_POSSIBLE option to ensure that it
> correctly depends on these PowerPC configurations being enabled. As a result,
> it prevents the HOTPLUG_CPU from being selected when the required dependencies
> are not satisfied.
>
> This change aligns the dependency tree with the expected hardware support for
> CPU hot-plugging under PowerPC architectures, ensuring that the kernel
> configuration steps do not lead to inconsistent states.
>
> Signed-off-by: Vishal Chourasia <[email-masked]>
> ---
> During the configuration process with 'make randconfig' followed by
> 'make olddefconfig', we observed a warning indicating an unmet direct
> dependency for the HOTPLUG_CPU option. The dependency in question relates to
> various PowerPC configurations (PPC_PSERIES, PPC_PMAC, PPC_POWERNV,
> FSL_SOC_BOOKE) which were not enabled, yet the HOTPLUG_CPU was being
> erroneously selected due to an implicit assumption by the PM_SLEEP_SMP option.
> This misalignment in dependencies could potentially lead to inconsistent kernel
> configuration states, especially when considering the necessary hardware
> support for CPU hot-plugging on PowerPC platforms. The patch aims to correct
> this by ensuring that ARCH_HIBERNATION_POSSIBLE is contingent upon the
> appropriate PowerPC configurations being active.
>
> steps to reproduce (before applying the patch):
>
> Run 'make pseries_le_defconfig'
> Run 'make menuconfig'
> Enable hibernation [ Kernel options -> Hibernation (aka 'suspend to disk') ] 
> Disable [ Platform support -> IBM PowerNV (Non-Virtualized) platform support ]
> Disable [ Platform support -> IBM pSeries & new (POWER5-based) iSeries ]
> Enable SMP [ Processor support -> Symmetric multi-processing support ]
> Save the config
> Run 'make olddefconfig'
>
>  arch/powerpc/Kconfig | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 6f105ee4f3cf..bf99ff9869f6 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -380,8 +380,9 @@ config DEFAULT_UIMAGE
>  	  Used to allow a board to specify it wants a uImage built by default
>  
>  config ARCH_HIBERNATION_POSSIBLE
> -	bool
> -	default y
> +	def_bool y
> +	depends on PPC_PSERIES || \
> +		PPC_PMAC || PPC_POWERNV || FSL_SOC_BOOKE
>  
>  config ARCH_SUSPEND_POSSIBLE
>  	def_bool y
>

I am wondering whether it should be switched to using select from
config PPC? 

-aneesh