[PATCH] rpm: pm: enable PM_RPM_EXCEPTION config flag

[Guan-Yu Lin <guanyulin@google.com>]

Introducing PM_RPM_EXCEPTION config flag, which may alter the priority
between system power management and runtime power management. In
suspend-to-idle flow, PM core will suspend all devices to avoid device
interact with the system. However, chances are devices might be used by
other systems rather than a single system. In this case, PM core shouldn't
suspend the devices. One may use PM_RPM_EXCEPTION config flag to mark
such exception, and determine the power state of a device with runtime
power management rather than system power management.

Signed-off-by: Guan-Yu Lin <guanyulin@google.com>
---
 drivers/usb/core/generic.c |  6 ++++++
 drivers/usb/core/usb.h     | 16 ++++++++++++++++
 kernel/power/Kconfig       |  8 ++++++++
 3 files changed, 30 insertions(+)

diff --git a/drivers/usb/core/generic.c b/drivers/usb/core/generic.c
index 740342a2812a..bb0dfcfc9764 100644
--- a/drivers/usb/core/generic.c
+++ b/drivers/usb/core/generic.c
@@ -266,6 +266,9 @@ int usb_generic_driver_suspend(struct usb_device *udev, pm_message_t msg)
 {
 	int rc;
 
+	if (usb_runtime_pm_exception(udev))
+		return 0;
+
 	/* Normal USB devices suspend through their upstream port.
 	 * Root hubs don't have upstream ports to suspend,
 	 * so we have to shut down their downstream HC-to-USB
@@ -294,6 +297,9 @@ int usb_generic_driver_resume(struct usb_device *udev, pm_message_t msg)
 {
 	int rc;
 
+	if (usb_runtime_pm_exception(udev))
+		return 0;
+
 	/* Normal USB devices resume/reset through their upstream port.
 	 * Root hubs don't have upstream ports to resume or reset,
 	 * so we have to start up their downstream HC-to-USB
diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index 60363153fc3f..14a054f814a2 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -90,6 +90,22 @@ extern void usb_major_cleanup(void);
 extern int usb_device_supports_lpm(struct usb_device *udev);
 extern int usb_port_disable(struct usb_device *udev);
 
+#ifdef	CONFIG_PM_RPM_EXCEPTION
+
+static inline int usb_runtime_pm_exception(struct usb_device *udev)
+{
+	return atomic_read(&udev->dev.power.usage_count);
+}
+
+#else
+
+static inline int usb_runtime_pm_exception(struct usb_device *udev)
+{
+	return 0;
+}
+
+#endif
+
 #ifdef	CONFIG_PM
 
 extern int usb_suspend(struct device *dev, pm_message_t msg);
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 4b31629c5be4..beba7a0f3947 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -193,6 +193,14 @@ config PM
 	  responsible for the actual handling of device suspend requests and
 	  wake-up events.
 
+config PM_RPM_EXCEPTION
+	bool "Prioritize Runtime Power Management more than Power Management"
+	default n
+	help
+	Provides a way to prioritize Runtime Power Management more than Power
+	Management. This way system can suspnd with maintaining specific
+	components in operation.
+
 config PM_DEBUG
 	bool "Power Management Debug Support"
 	depends on PM
-- 
2.42.0.820.g83a721a137-goog