linux-kernel - [tip: sched/core] cpuidle, tegra: Push RCU-idle into driver

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Date:   Fri, 13 Jan 2023 12:31:14 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Tony Lindgren <tony@...mide.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] cpuidle, tegra: Push RCU-idle into driver

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     5fca0d9f5d76664786ca6c09076341def165a677
Gitweb:        https://git.kernel.org/tip/5fca0d9f5d76664786ca6c09076341def165a677
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Thu, 12 Jan 2023 20:43:20 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Fri, 13 Jan 2023 11:03:22 +01:00

cpuidle, tegra: 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.

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

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Tested-by: Tony Lindgren <tony@...mide.com>
Tested-by: Ulf Hansson <ulf.hansson@...aro.org>
Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Link: https://lore.kernel.org/r/20230112195539.699546331@infradead.org
---
 drivers/cpuidle/cpuidle-tegra.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-tegra.c b/drivers/cpuidle/cpuidle-tegra.c
index 9845629..3ca5cfb 100644
--- a/drivers/cpuidle/cpuidle-tegra.c
+++ b/drivers/cpuidle/cpuidle-tegra.c
@@ -180,9 +180,11 @@ static int tegra_cpuidle_state_enter(struct cpuidle_device *dev,
 	}
 
 	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(struct cpuidle_device *dev,
 		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 cpuidle_device *dev,
 			       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 cpuidle_device *dev,
 	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_driver = {
 			.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_driver = {
 			.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",