linux-kernel - [PATCH v1 2/3] PM: runtime: Introduce pm_runtime

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Message-ID: <8497121.T7Z3S40VBb@rjwysocki.net>
Date: Mon, 17 Feb 2025 21:16:43 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Alan Stern <stern@...land.harvard.edu>, Bjorn Helgaas <helgaas@...nel.org>,
 Linux PCI <linux-pci@...r.kernel.org>, Ulf Hansson <ulf.hansson@...aro.org>,
 Johan Hovold <johan@...nel.org>,
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
 Jon Hunter <jonathanh@...dia.com>, Linux ACPI <linux-acpi@...r.kernel.org>,
 Mika Westerberg <mika.westerberg@...ux.intel.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH v1 2/3] PM: runtime: Introduce pm_runtime_blocked()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Introduce a new helper function called pm_runtime_blocked() for
checking the power.last_status value indicating whether or not the
enabling of runtime PM for the given device has been blocked (which
happens in the "prepare" phase of system-wide suspend if runtime
PM is disabled for the given device at that point and has never
been enabled so far).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/base/power/runtime.c |   17 +++++++++++++++++
 include/linux/pm_runtime.h   |    2 ++
 2 files changed, 19 insertions(+)

--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1555,6 +1555,23 @@
 }
 EXPORT_SYMBOL_GPL(pm_runtime_enable);

+bool pm_runtime_blocked(struct device *dev)
+{
+	bool ret;
+
+	/*
+	 * dev->power.last_status is a bit field, so in case it is updated via
+	 * RMW, read it under the spin lock.
+	 */
+	spin_lock_irq(&dev->power.lock);
+
+	ret = dev->power.last_status == RPM_BLOCKED;
+
+	spin_unlock_irq(&dev->power.lock);
+
+	return ret;
+}
+
 static void pm_runtime_disable_action(void *data)
 {
 	pm_runtime_dont_use_autosuspend(data);
--- a/include/linux/pm_runtime.h
+++ b/include/linux/pm_runtime.h
@@ -81,6 +81,7 @@
 extern void pm_runtime_unblock(struct device *dev);
 extern void pm_runtime_enable(struct device *dev);
 extern void __pm_runtime_disable(struct device *dev, bool regular);
+extern bool pm_runtime_blocked(struct device *dev);
 extern void pm_runtime_allow(struct device *dev);
 extern void pm_runtime_forbid(struct device *dev);
 extern void pm_runtime_no_callbacks(struct device *dev);
@@ -277,6 +278,7 @@
 static inline void pm_runtime_unblock(struct device *dev) {}
 static inline void pm_runtime_enable(struct device *dev) {}
 static inline void __pm_runtime_disable(struct device *dev, bool c) {}
+static inline bool pm_runtime_blocked(struct device *dev) { return true; }
 static inline void pm_runtime_allow(struct device *dev) {}
 static inline void pm_runtime_forbid(struct device *dev) {}