[PATCH v2 4/5] PM: Allow calling dev_pm_domain_set() with raw spinlock

[Krzysztof Kozlowski]

device_pm_check_callbacks() uses dev->power spinlock, which on
PREEMPT_RT sleeps.  However some PM domains on PREEMPT_RT might be using
raw spinlocks as genpd_lock(), thus dev_pm_domain_set() must not call
device_pm_check_callbacks().  In fact device_pm_check_callbacks() is not
strictly related to dev_pm_domain_set() and calls for these two can be
made separately.

Add new helper dev_pm_domain_set_no_cb() which will only set PM domain
but will not check the callbacks, leaving the checl to the caller.

Cc: Adrien Thierry <athierry@xxxxxxxxxx>
Cc: Brian Masney <bmasney@xxxxxxxxxx>
Cc: linux-rt-users@xxxxxxxxxxxxxxx
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
---
 drivers/base/power/common.c | 27 +++++++++++++++++++++++++--
 include/linux/pm_domain.h   |  3 +++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/drivers/base/power/common.c b/drivers/base/power/common.c
index 72115917e0bd..f81cab6990ad 100644
--- a/drivers/base/power/common.c
+++ b/drivers/base/power/common.c
@@ -218,6 +218,30 @@ EXPORT_SYMBOL_GPL(dev_pm_domain_start);
  * This function must be called with the device lock held.
  */
 void dev_pm_domain_set(struct device *dev, struct dev_pm_domain *pd)
+{
+	if (dev->pm_domain == pd)
+		return;
+
+	dev_pm_domain_set_no_cb(dev, pd);
+	device_pm_check_callbacks(dev);
+}
+EXPORT_SYMBOL_GPL(dev_pm_domain_set);
+
+/**
+ * dev_pm_domain_set_no_cb - Set PM domain of a device.
+ * @dev: Device whose PM domain is to be set.
+ * @pd: PM domain to be set, or NULL.
+ *
+ * Sets the PM domain the device belongs to. The PM domain of a device needs
+ * to be set before its probe finishes (it's bound to a driver).
+ *
+ * This is exactly like dev_pm_domain_set(), however device_pm_check_callbacks()
+ * is not called and the caller is responsible to invoke
+ * device_pm_check_callbacks() with device lock held.
+ *
+ * This function must be called with the device lock held.
+ */
+void dev_pm_domain_set_no_cb(struct device *dev, struct dev_pm_domain *pd)
 {
 	if (dev->pm_domain == pd)
 		return;
@@ -225,6 +249,5 @@ void dev_pm_domain_set(struct device *dev, struct dev_pm_domain *pd)
 	WARN(pd && device_is_bound(dev),
 	     "PM domains can only be changed for unbound devices\n");
 	dev->pm_domain = pd;
-	device_pm_check_callbacks(dev);
 }
-EXPORT_SYMBOL_GPL(dev_pm_domain_set);
+EXPORT_SYMBOL_GPL(dev_pm_domain_set_no_cb);
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 0a1600244963..352d0c76bfec 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -438,6 +438,7 @@ struct device *dev_pm_domain_attach_by_name(struct device *dev,
 void dev_pm_domain_detach(struct device *dev, bool power_off);
 int dev_pm_domain_start(struct device *dev);
 void dev_pm_domain_set(struct device *dev, struct dev_pm_domain *pd);
+void dev_pm_domain_set_no_cb(struct device *dev, struct dev_pm_domain *pd);
 #else
 static inline int dev_pm_domain_attach(struct device *dev, bool power_on)
 {
@@ -460,6 +461,8 @@ static inline int dev_pm_domain_start(struct device *dev)
 }
 static inline void dev_pm_domain_set(struct device *dev,
 				     struct dev_pm_domain *pd) {}
+static inline void dev_pm_domain_set_no_cb(struct device *dev,
+					   struct dev_pm_domain *pd) {}
 #endif
 
 #endif /* _LINUX_PM_DOMAIN_H */
-- 
2.34.1