linux-kernel - [PATCH v2 2/4] pmdomain: Respect the CPU system-wakeup QoS limit during s2idle

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Message-ID: <20251016151929.75863-3-ulf.hansson@linaro.org>
Date: Thu, 16 Oct 2025 17:19:22 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: "Rafael J . Wysocki" <rafael@...nel.org>,
	linux-pm@...r.kernel.org
Cc: Vincent Guittot <vincent.guittot@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Kevin Hilman <khilman@...libre.com>,
	Pavel Machek <pavel@...nel.org>,
	Len Brown <len.brown@...el.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Maulik Shah <quic_mkshah@...cinc.com>,
	Prasad Sodagudi <psodagud@...cinc.com>,
	Dhruva Gole <d-gole@...com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/4] pmdomain: Respect the CPU system-wakeup QoS limit during s2idle

A CPU system-wakeup QoS limit may have been requested by user-space. To
avoid breaking this constraint when entering a low-power state during
s2idle through genpd, let's extend the corresponding genpd governor for
CPUs. More precisely, during s2idle let the genpd governor select a
suitable low-power state, by taking into account the QoS limit.

Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---

Changes in v2:
	- Limite the change to the genpd governor for CPUs.

---
 drivers/pmdomain/core.c     | 10 ++++++++--
 drivers/pmdomain/governor.c | 27 +++++++++++++++++++++++++++
 include/linux/pm_domain.h   |  1 +
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
index 61c2277c9ce3..4fd546ef0448 100644
--- a/drivers/pmdomain/core.c
+++ b/drivers/pmdomain/core.c
@@ -1425,8 +1425,14 @@ static void genpd_sync_power_off(struct generic_pm_domain *genpd, bool use_lock,
 			return;
 	}
 
-	/* Choose the deepest state when suspending */
-	genpd->state_idx = genpd->state_count - 1;
+	if (genpd->gov && genpd->gov->system_power_down_ok) {
+		if (!genpd->gov->system_power_down_ok(&genpd->domain))
+			return;
+	} else {
+		/* Default to the deepest state. */
+		genpd->state_idx = genpd->state_count - 1;
+	}
+
 	if (_genpd_power_off(genpd, false)) {
 		genpd->states[genpd->state_idx].rejected++;
 		return;
diff --git a/drivers/pmdomain/governor.c b/drivers/pmdomain/governor.c
index 39359811a930..bd1b9d66d4a5 100644
--- a/drivers/pmdomain/governor.c
+++ b/drivers/pmdomain/governor.c
@@ -415,9 +415,36 @@ static bool cpu_power_down_ok(struct dev_pm_domain *pd)
 	return false;
 }
 
+static bool cpu_system_power_down_ok(struct dev_pm_domain *pd)
+{
+	s64 constraint_ns = cpu_wakeup_latency_qos_limit() * NSEC_PER_USEC;
+	struct generic_pm_domain *genpd = pd_to_genpd(pd);
+	int state_idx = genpd->state_count - 1;
+
+	if (!(genpd->flags & GENPD_FLAG_CPU_DOMAIN)) {
+		genpd->state_idx = state_idx;
+		return true;
+	}
+
+	/* Find the deepest state for the latency constraint. */
+	while (state_idx >= 0) {
+		s64 latency_ns = genpd->states[state_idx].power_off_latency_ns +
+				 genpd->states[state_idx].power_on_latency_ns;
+
+		if (latency_ns <= constraint_ns) {
+			genpd->state_idx = state_idx;
+			return true;
+		}
+		state_idx--;
+	}
+
+	return false;
+}
+
 struct dev_power_governor pm_domain_cpu_gov = {
 	.suspend_ok = default_suspend_ok,
 	.power_down_ok = cpu_power_down_ok,
+	.system_power_down_ok = cpu_system_power_down_ok,
 };
 #endif
 
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index f67a2cb7d781..93ba0143ca47 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -153,6 +153,7 @@ enum genpd_sync_state {
 };
 
 struct dev_power_governor {
+	bool (*system_power_down_ok)(struct dev_pm_domain *domain);
 	bool (*power_down_ok)(struct dev_pm_domain *domain);
 	bool (*suspend_ok)(struct device *dev);
 };
-- 
2.43.0