cpuidle, dt: Push RCU-idle into driver

Doing RCU-idle outside the driver, only to then temporarily enable it
again before going idle is suboptimal.

Notably: this converts all dt_init_idle_driver() and
__CPU_PM_CPU_IDLE_ENTER() users for they are inextrably intertwined.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230112195540.068981667@infradead.org

drivers/acpi/processor_idle.c

@@ -1219,6 +1219,8 @@ static int acpi_processor_setup_lpi_states(struct acpi_processor *pr)
 		state->target_residency = lpi->min_residency;
 		if (lpi->arch_flags)
 			state->flags |= CPUIDLE_FLAG_TIMER_STOP;
+		if (i != 0 && lpi->entry_method == ACPI_CSTATE_FFH)
+			state->flags |= CPUIDLE_FLAG_RCU_IDLE;
 		state->enter = acpi_idle_lpi_enter;
 		drv->safe_state_index = i;
 	}

drivers/cpuidle/cpuidle-big_little.c

@@ -64,7 +64,8 @@ static struct cpuidle_driver bl_idle_little_driver = {
 		.enter			= bl_enter_powerdown,
 		.exit_latency		= 700,
 		.target_residency	= 2500,
-		.flags			= CPUIDLE_FLAG_TIMER_STOP,
+		.flags			= CPUIDLE_FLAG_TIMER_STOP |
+					  CPUIDLE_FLAG_RCU_IDLE,
 		.name			= "C1",
 		.desc			= "ARM little-cluster power down",
 	},
@@ -85,7 +86,8 @@ static struct cpuidle_driver bl_idle_big_driver = {
 		.enter			= bl_enter_powerdown,
 		.exit_latency		= 500,
 		.target_residency	= 2000,
-		.flags			= CPUIDLE_FLAG_TIMER_STOP,
+		.flags			= CPUIDLE_FLAG_TIMER_STOP |
+					  CPUIDLE_FLAG_RCU_IDLE,
 		.name			= "C1",
 		.desc			= "ARM big-cluster power down",
 	},
@@ -124,11 +126,13 @@ static int bl_enter_powerdown(struct cpuidle_device *dev,
 				struct cpuidle_driver *drv, int idx)
 {
 	cpu_pm_enter();
+	ct_idle_enter();
 
 	cpu_suspend(0, bl_powerdown_finisher);
 
 	/* signals the MCPM core that CPU is out of low power state */
 	mcpm_cpu_powered_up();
+	ct_idle_exit();
 
 	cpu_pm_exit();
 

drivers/cpuidle/dt_idle_states.c

@@ -77,7 +77,7 @@ static int init_state_node(struct cpuidle_state *idle_state,
 	if (err)
 		desc = state_node->name;
 
-	idle_state->flags = 0;
+	idle_state->flags = CPUIDLE_FLAG_RCU_IDLE;
 	if (of_property_read_bool(state_node, "local-timer-stop"))
 		idle_state->flags |= CPUIDLE_FLAG_TIMER_STOP;
 	/*

include/linux/cpuidle.h

@@ -289,7 +289,9 @@ extern s64 cpuidle_governor_latency_req(unsigned int cpu);
 	if (!is_retention)						\
 		__ret =  cpu_pm_enter();				\
 	if (!__ret) {							\
+		ct_idle_enter();					\
 		__ret = low_level_idle_enter(state);			\
+		ct_idle_exit();						\
 		if (!is_retention)					\
 			cpu_pm_exit();					\
 	}								\