[PATCH v3 06/51] cpuidle,tegra: Push RCU-idle into driver

Peter Zijlstra
Thu, 12 Jan 2023 19:43:20 -0000

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

Notably once implicitly through the cpu_pm_*() calls and once
explicitly doing RCU_NONIDLE().

Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
Reviewed-by: Frederic Weisbecker <frederic at kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Tested-by: Tony Lindgren <tony at atomide.com>
Tested-by: Ulf Hansson <ulf.hansson at linaro.org>
---
 drivers/cpuidle/cpuidle-tegra.c |   21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

--- a/drivers/cpuidle/cpuidle-tegra.c
+++ b/drivers/cpuidle/cpuidle-tegra.c
@@ -180,9 +180,11 @@ static int tegra_cpuidle_state_enter(str
 	}

 	local_fiq_disable();
-	RCU_NONIDLE(tegra_pm_set_cpu_in_lp2());
+	tegra_pm_set_cpu_in_lp2();
 	cpu_pm_enter();

+	ct_idle_enter();
+
 	switch (index) {
 	case TEGRA_C7:
 		err = tegra_cpuidle_c7_enter();
@@ -197,8 +199,10 @@ static int tegra_cpuidle_state_enter(str
 		break;
 	}

+	ct_idle_exit();
+
 	cpu_pm_exit();
-	RCU_NONIDLE(tegra_pm_clear_cpu_in_lp2());
+	tegra_pm_clear_cpu_in_lp2();
 	local_fiq_enable();

 	return err ?: index;
@@ -226,6 +230,7 @@ static int tegra_cpuidle_enter(struct cp
 			       struct cpuidle_driver *drv,
 			       int index)
 {
+	bool do_rcu = drv->states[index].flags & CPUIDLE_FLAG_RCU_IDLE;
 	unsigned int cpu = cpu_logical_map(dev->cpu);
 	int ret;

@@ -233,9 +238,13 @@ static int tegra_cpuidle_enter(struct cp
 	if (dev->states_usage[index].disable)
 		return -1;

-	if (index == TEGRA_C1)
+	if (index == TEGRA_C1) {
+		if (do_rcu)
+			ct_idle_enter();
 		ret = arm_cpuidle_simple_enter(dev, drv, index);
-	else
+		if (do_rcu)
+			ct_idle_exit();
+	} else
 		ret = tegra_cpuidle_state_enter(dev, index, cpu);

 	if (ret < 0) {
@@ -285,7 +294,8 @@ static struct cpuidle_driver tegra_idle_
 			.exit_latency		= 2000,
 			.target_residency	= 2200,
 			.power_usage		= 100,
-			.flags			= CPUIDLE_FLAG_TIMER_STOP,
+			.flags			= CPUIDLE_FLAG_TIMER_STOP |
+						  CPUIDLE_FLAG_RCU_IDLE,
 			.name			= "C7",
 			.desc			= "CPU core powered off",
 		},
@@ -295,6 +305,7 @@ static struct cpuidle_driver tegra_idle_
 			.target_residency	= 10000,
 			.power_usage		= 0,
 			.flags			= CPUIDLE_FLAG_TIMER_STOP |
+						  CPUIDLE_FLAG_RCU_IDLE   |
 						  CPUIDLE_FLAG_COUPLED,
 			.name			= "CC6",
 			.desc			= "CPU cluster powered off",