linux-kernel - [PATCH 3/6] cpuidle: psci-domain: Enable system-wide suspend on PREEMPT

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Message-Id: <20240429140531.210576-4-ulf.hansson@linaro.org>
Date: Mon, 29 Apr 2024 16:05:28 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: "Rafael J . Wysocki" <rafael@...nel.org>,
	Sudeep Holla <sudeep.holla@....com>,
	linux-pm@...r.kernel.org
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Nikunj Kela <nkela@...cinc.com>,
	Prasad Sodagudi <psodagud@...cinc.com>,
	Maulik Shah <quic_mkshah@...cinc.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	linux-rt-users@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/6] cpuidle: psci-domain: Enable system-wide suspend on PREEMPT_RT

The domain-idle-states are currently disabled on a PREEMPT_RT based
configuration for the cpuidle-psci-domain. To enable them to be used for
system-wide suspend and in particular during s2idle, let's set the
GENPD_FLAG_RPM_ALWAYS_ON instead of GENPD_FLAG_ALWAYS_ON for the
corresponding genpd provider.

In this way, the runtime PM path remains disabled in genpd for its attached
devices, while powering-on/off the PM domain during system-wide suspend
becomes allowed.

Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---
 drivers/cpuidle/cpuidle-psci-domain.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
index fae958794339..ea28b73ef3fb 100644
--- a/drivers/cpuidle/cpuidle-psci-domain.c
+++ b/drivers/cpuidle/cpuidle-psci-domain.c
@@ -67,12 +67,16 @@ static int psci_pd_init(struct device_node *np, bool use_osi)
 
 	/*
 	 * Allow power off when OSI has been successfully enabled.
-	 * PREEMPT_RT is not yet ready to enter domain idle states.
+	 * On a PREEMPT_RT based configuration the domain idle states are
+	 * supported, but only during system-wide suspend.
 	 */
-	if (use_osi && !IS_ENABLED(CONFIG_PREEMPT_RT))
+	if (use_osi) {
 		pd->power_off = psci_pd_power_off;
-	else
+		if (IS_ENABLED(CONFIG_PREEMPT_RT))
+			pd->flags |= GENPD_FLAG_RPM_ALWAYS_ON;
+	} else {
 		pd->flags |= GENPD_FLAG_ALWAYS_ON;
+	}
 
 	/* Use governor for CPU PM domains if it has some states to manage. */
 	pd_gov = pd->states ? &pm_domain_cpu_gov : NULL;
-- 
2.34.1