linux-kernel - [PATCH 1/2] PM / QoS: add flag to indicate latency applies system-wide

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Message-Id: <20260120-topic-lpm-pmdomain-device-constraints-v1-1-108fc4cfafce@baylibre.com>
Date: Tue, 20 Jan 2026 17:54:44 -0800
From: "Kevin Hilman (TI)" <khilman@...libre.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>, 
 Ulf Hansson <ulf.hansson@...aro.org>, linux-pm@...r.kernel.org
Cc: Dhruva Gole <d-gole@...com>, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] PM / QoS: add flag to indicate latency applies
 system-wide

By default, the QoS resume latency currenly only applied to runtime PM
decisions.

Add new PM_QOS_FLAG_LATENCY_SYS flag to indicate that the
resume latency QoS constraint should be applied to system-wide
PM, and *not* runtime PM.

Signed-off-by: Kevin Hilman (TI) <khilman@...libre.com>
---
 drivers/base/power/sysfs.c | 27 +++++++++++++++++++++++++++
 include/linux/pm_qos.h     |  2 ++
 2 files changed, 29 insertions(+)

diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
index 13b31a3adc77..9136c13c17e4 100644
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -316,6 +316,32 @@ static ssize_t pm_qos_no_power_off_store(struct device *dev,
 
 static DEVICE_ATTR_RW(pm_qos_no_power_off);
 
+static ssize_t pm_qos_latency_sys_show(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	return sysfs_emit(buf, "%d\n", !!(dev_pm_qos_requested_flags(dev)
+					  & PM_QOS_FLAG_LATENCY_SYS));
+}
+
+static ssize_t pm_qos_latency_sys_store(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t n)
+{
+	int ret;
+
+	if (kstrtoint(buf, 0, &ret))
+		return -EINVAL;
+
+	if (ret != 0 && ret != 1)
+		return -EINVAL;
+
+	ret = dev_pm_qos_update_flags(dev, PM_QOS_FLAG_LATENCY_SYS, ret);
+	return ret < 0 ? ret : n;
+}
+
+static DEVICE_ATTR_RW(pm_qos_latency_sys);
+
 #ifdef CONFIG_PM_SLEEP
 static const char _enabled[] = "enabled";
 static const char _disabled[] = "disabled";
@@ -681,6 +707,7 @@ static const struct attribute_group pm_qos_latency_tolerance_attr_group = {
 
 static struct attribute *pm_qos_flags_attrs[] = {
 	&dev_attr_pm_qos_no_power_off.attr,
+	&dev_attr_pm_qos_latency_sys.attr,
 	NULL,
 };
 static const struct attribute_group pm_qos_flags_attr_group = {
diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
index 6cea4455f867..aededda52b6b 100644
--- a/include/linux/pm_qos.h
+++ b/include/linux/pm_qos.h
@@ -37,6 +37,8 @@ enum pm_qos_flags_status {
 #define PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT	(-1)
 
 #define PM_QOS_FLAG_NO_POWER_OFF	(1 << 0)
+/* latency value applies to system-wide suspend/s2idle */
+#define PM_QOS_FLAG_LATENCY_SYS		(2 << 0)
 
 enum pm_qos_type {
 	PM_QOS_UNITIALIZED,

-- 
2.51.0