linux-kernel - [RFC/PATCH 2/3] pmdomain: Respect the system-wakeup QoS limit at system-wide suspend

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250716123323.65441-3-ulf.hansson@linaro.org>
Date: Wed, 16 Jul 2025 14:33:18 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: "Rafael J . Wysocki" <rafael@...nel.org>,
	linux-pm@...r.kernel.org
Cc: 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>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	linux-kernel@...r.kernel.org
Subject: [RFC/PATCH 2/3] pmdomain: Respect the system-wakeup QoS limit at system-wide suspend

A system-wakeup QoS limit may have been requested by user-space. To avoid
entering a too deep state for PM domains that are managed my genpd, let's
start to take into account the QoS limit when selecting the
low-power-state.

If it turns out that none of the states in the list of domain-idlestates
are suitable to use, let's leave the PM domain powered-on.

Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---
 drivers/pmdomain/core.c     | 10 ++++++++--
 drivers/pmdomain/governor.c | 23 +++++++++++++++++++++++
 include/linux/pm_domain.h   |  1 +
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
index a86aeda1c955..5cbe7473c2b9 100644
--- a/drivers/pmdomain/core.c
+++ b/drivers/pmdomain/core.c
@@ -1396,8 +1396,14 @@ 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..2630ba6f28ef 100644
--- a/drivers/pmdomain/governor.c
+++ b/drivers/pmdomain/governor.c
@@ -343,6 +343,27 @@ static bool default_power_down_ok(struct dev_pm_domain *pd)
 	return _default_power_down_ok(pd, ktime_get());
 }
 
+static bool default_system_power_down_ok(struct dev_pm_domain *pd)
+{
+	s64 constraint_ns = system_wakeup_latency_qos_limit() * NSEC_PER_USEC;
+	struct generic_pm_domain *genpd = pd_to_genpd(pd);
+	int state_idx = genpd->state_count - 1;
+
+	/* 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;
+}
+
 #ifdef CONFIG_CPU_IDLE
 static bool cpu_power_down_ok(struct dev_pm_domain *pd)
 {
@@ -418,12 +439,14 @@ static bool cpu_power_down_ok(struct dev_pm_domain *pd)
 struct dev_power_governor pm_domain_cpu_gov = {
 	.suspend_ok = default_suspend_ok,
 	.power_down_ok = cpu_power_down_ok,
+	.system_power_down_ok = default_system_power_down_ok,
 };
 #endif
 
 struct dev_power_governor simple_qos_governor = {
 	.suspend_ok = default_suspend_ok,
 	.power_down_ok = default_power_down_ok,
+	.system_power_down_ok = default_system_power_down_ok,
 };
 
 /*
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 99556589f45e..0ad14cc4ad7f 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -140,6 +140,7 @@ 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