cpuidle, riscv: Push RCU-idle into driver

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

That is, once implicitly through the cpu_pm_*() calls and once
explicitly doing ct_irq_*_irqon().
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>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20230112195539.637185846@infradead.org

drivers/cpuidle/cpuidle-riscv-sbi.c

@@ -121,12 +121,12 @@ static int __sbi_enter_domain_idle_state(struct cpuidle_device *dev,
 		return -1;
 
 	/* Do runtime PM to manage a hierarchical CPU toplogy. */
-	ct_irq_enter_irqson();
 	if (s2idle)
 		dev_pm_genpd_suspend(pd_dev);
 	else
 		pm_runtime_put_sync_suspend(pd_dev);
-	ct_irq_exit_irqson();
+
+	ct_idle_enter();
 
 	if (sbi_is_domain_state_available())
 		state = sbi_get_domain_state();
@@ -135,12 +135,12 @@ static int __sbi_enter_domain_idle_state(struct cpuidle_device *dev,
 
 	ret = sbi_suspend(state) ? -1 : idx;
 
-	ct_irq_enter_irqson();
+	ct_idle_exit();
+
 	if (s2idle)
 		dev_pm_genpd_resume(pd_dev);
 	else
 		pm_runtime_get_sync(pd_dev);
-	ct_irq_exit_irqson();
 
 	cpu_pm_exit();
 
@@ -251,6 +251,7 @@ static int sbi_dt_cpu_init_topology(struct cpuidle_driver *drv,
 	 * of a shared state for the domain, assumes the domain states are all
 	 * deeper states.
 	 */
+	drv->states[state_count - 1].flags |= CPUIDLE_FLAG_RCU_IDLE;
 	drv->states[state_count - 1].enter = sbi_enter_domain_idle_state;
 	drv->states[state_count - 1].enter_s2idle =
 					sbi_enter_s2idle_domain_idle_state;