[v8,02/11] cpuidle: rename ARCH_HAS_CPU_RELAX to ARCH_HAS_OPTIMIZED_POLL

Commit Message

Ankur Arora Sept. 25, 2024, 11:24 p.m. UTC

ARCH_HAS_CPU_RELAX is defined on architectures that provide an
primitive (via cpu_relax()) that can be used as part of a polling
mechanism -- one that would be cheaper than spinning in a tight
loop.

However, recent changes in poll_idle() mean that a higher level
primitive -- smp_cond_load_relaxed() is used for polling. This would
in-turn use cpu_relax() or an architecture specific implementation.
On ARM64 in particular this turns into a WFE which waits on a store
to a cacheline instead of a busy poll.

Accordingly condition the polling drivers on ARCH_HAS_OPTIMIZED_POLL
instead of ARCH_HAS_CPU_RELAX. While at it, make both intel-idle
and cpuidle-haltpoll explicitly depend on ARCH_HAS_CPU_RELAX.

Suggested-by: Will Deacon <[e-mail]>
Signed-off-by: Ankur Arora <[e-mail]>
---
 arch/x86/Kconfig              | 2 +-
 drivers/acpi/processor_idle.c | 4 ++--
 drivers/cpuidle/Kconfig       | 2 +-
 drivers/cpuidle/Makefile      | 2 +-
 drivers/idle/Kconfig          | 1 +
 include/linux/cpuidle.h       | 2 +-
 6 files changed, 7 insertions(+), 6 deletions(-)

Patch

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2852fcd82cbd..555871e7e3b2 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -378,7 +378,7 @@  config ARCH_MAY_HAVE_PC_FDC
 config GENERIC_CALIBRATE_DELAY
 	def_bool y
 
-config ARCH_HAS_CPU_RELAX
+config ARCH_HAS_OPTIMIZED_POLL
 	def_bool y
 
 config ARCH_HIBERNATION_POSSIBLE
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 831fa4a12159..44096406d65d 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -35,7 +35,7 @@ 
 #include <asm/cpu.h>
 #endif
 
-#define ACPI_IDLE_STATE_START	(IS_ENABLED(CONFIG_ARCH_HAS_CPU_RELAX) ? 1 : 0)
+#define ACPI_IDLE_STATE_START	(IS_ENABLED(CONFIG_ARCH_HAS_OPTIMIZED_POLL) ? 1 : 0)
 
 static unsigned int max_cstate __read_mostly = ACPI_PROCESSOR_MAX_POWER;
 module_param(max_cstate, uint, 0400);
@@ -782,7 +782,7 @@  static int acpi_processor_setup_cstates(struct acpi_processor *pr)
 	if (max_cstate == 0)
 		max_cstate = 1;
 
-	if (IS_ENABLED(CONFIG_ARCH_HAS_CPU_RELAX)) {
+	if (IS_ENABLED(CONFIG_ARCH_HAS_OPTIMIZED_POLL)) {
 		cpuidle_poll_state_init(drv);
 		count = 1;
 	} else {
diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig
index cac5997dca50..75f6e176bbc8 100644
--- a/drivers/cpuidle/Kconfig
+++ b/drivers/cpuidle/Kconfig
@@ -73,7 +73,7 @@  endmenu
 
 config HALTPOLL_CPUIDLE
 	tristate "Halt poll cpuidle driver"
-	depends on X86 && KVM_GUEST
+	depends on X86 && KVM_GUEST && ARCH_HAS_OPTIMIZED_POLL
 	select CPU_IDLE_GOV_HALTPOLL
 	default y
 	help
diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile
index d103342b7cfc..f29dfd1525b0 100644
--- a/drivers/cpuidle/Makefile
+++ b/drivers/cpuidle/Makefile
@@ -7,7 +7,7 @@  obj-y += cpuidle.o driver.o governor.o sysfs.o governors/
 obj-$(CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED) += coupled.o
 obj-$(CONFIG_DT_IDLE_STATES)		  += dt_idle_states.o
 obj-$(CONFIG_DT_IDLE_GENPD)		  += dt_idle_genpd.o
-obj-$(CONFIG_ARCH_HAS_CPU_RELAX)	  += poll_state.o
+obj-$(CONFIG_ARCH_HAS_OPTIMIZED_POLL)	  += poll_state.o
 obj-$(CONFIG_HALTPOLL_CPUIDLE)		  += cpuidle-haltpoll.o
 
 ##################################################################################
diff --git a/drivers/idle/Kconfig b/drivers/idle/Kconfig
index 6707d2539fc4..6f9b1d48fede 100644
--- a/drivers/idle/Kconfig
+++ b/drivers/idle/Kconfig
@@ -4,6 +4,7 @@  config INTEL_IDLE
 	depends on CPU_IDLE
 	depends on X86
 	depends on CPU_SUP_INTEL
+	depends on ARCH_HAS_OPTIMIZED_POLL
 	help
 	  Enable intel_idle, a cpuidle driver that includes knowledge of
 	  native Intel hardware idle features.  The acpi_idle driver
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 3183aeb7f5b4..7e7e58a17b07 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -275,7 +275,7 @@  static inline void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev,
 }
 #endif
 
-#if defined(CONFIG_CPU_IDLE) && defined(CONFIG_ARCH_HAS_CPU_RELAX)
+#if defined(CONFIG_CPU_IDLE) && defined(CONFIG_ARCH_HAS_OPTIMIZED_POLL)
 void cpuidle_poll_state_init(struct cpuidle_driver *drv);
 #else
 static inline void cpuidle_poll_state_init(struct cpuidle_driver *drv) {}