[PATCH v3] powerpc: Adjust config HOTPLUG_CPU dependency

[Vishal Chourasia]

Changed HOTPLUG_CPU dependency to SMP and either ARCH_HIBERNATION_POSSIBLE or
ARCH_SUSPEND_POSSIBLE, aligning with systems' suspend/hibernation capabilities.
This update link CPU hotplugging more logically with platforms' capabilities.

configs ARCH_HIBERNATION_POSSIBLE and ARCH_SUSPEND_POSSIBLE are now selected
only if required platform dependencies are met.

Reported-by: Srikar Dronamraju <srikar at linux.vnet.ibm.com>
Suggested-by: Aneesh Kumar K V <aneesh.kumar at linux.ibm.com>
Suggested-by: Michael Ellerman <mpe at ellerman.id.au>
Signed-off-by: Vishal Chourasia <vishalc at linux.ibm.com>

v2: https://lore.kernel.org/all/20231122092303.223719-1-vishalc@linux.ibm.com
v1: https://lore.kernel.org/all/20231114082046.6018-1-vishalc@linux.ibm.com
---
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 | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 6f105ee4f3cf..87c8134da3da 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -156,6 +156,7 @@ config PPC
 	select ARCH_HAS_UACCESS_FLUSHCACHE
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
+	select ARCH_HIBERNATION_POSSIBLE        if (PPC_PSERIES || PPC_PMAC || PPC_POWERNV || FSL_SOC_BOOKE)
 	select ARCH_KEEP_MEMBLOCK
 	select ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE	if PPC_RADIX_MMU
 	select ARCH_MIGHT_HAVE_PC_PARPORT
@@ -166,6 +167,7 @@ config PPC
 	select ARCH_STACKWALK
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_DEBUG_PAGEALLOC	if PPC_BOOK3S || PPC_8xx || 40x
+	select ARCH_SUSPEND_POSSIBLE            if (ADB_PMU || PPC_EFIKA || PPC_LITE5200 || PPC_83xx || (PPC_85xx && !PPC_E500MC) || PPC_86xx || PPC_PSERIES || 44x || 40x)
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF		if PPC64
 	select ARCH_USE_MEMTEST
@@ -381,13 +383,9 @@ config DEFAULT_UIMAGE
 
 config ARCH_HIBERNATION_POSSIBLE
 	bool
-	default y
 
 config ARCH_SUSPEND_POSSIBLE
-	def_bool y
-	depends on ADB_PMU || PPC_EFIKA || PPC_LITE5200 || PPC_83xx || \
-		   (PPC_85xx && !PPC_E500MC) || PPC_86xx || PPC_PSERIES \
-		   || 44x || 40x
+	bool
 
 config ARCH_SUSPEND_NONZERO_CPU
 	def_bool y
@@ -568,8 +566,7 @@ config ARCH_USING_PATCHABLE_FUNCTION_ENTRY
 
 config HOTPLUG_CPU
 	bool "Support for enabling/disabling CPUs"
-	depends on SMP && (PPC_PSERIES || \
-		PPC_PMAC || PPC_POWERNV || FSL_SOC_BOOKE)
+	depends on SMP && (ARCH_HIBERNATION_POSSIBLE || ARCH_SUSPEND_POSSIBLE)
 	help
 	  Say Y here to be able to disable and re-enable individual
 	  CPUs at runtime on SMP machines.
-- 
2.41.0