pmdomain: core: Introduce dev_pm_genpd_rpm_always_on()

For some usecases a consumer driver requires its device to remain power-on
from the PM domain perspective during runtime. Using dev PM qos along with
the genpd governors, doesn't work for this case as would potentially
prevent the device from being runtime suspended too.

To support these usecases, let's introduce dev_pm_genpd_rpm_always_on() to
allow consumers drivers to dynamically control the behaviour in genpd for a
device that is attached to it.

Signed-off-by: Ulf Hansson <[email protected]>
Signed-off-by: Shawn Lin <[email protected]>
Acked-by: Manivannan Sadhasivam <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Ulf Hansson <[email protected]>

Author: storulf

drivers/pmdomain/core.c

@@ -697,6 +697,37 @@ bool dev_pm_genpd_get_hwmode(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(dev_pm_genpd_get_hwmode);
 
+/**
+ * dev_pm_genpd_rpm_always_on() - Control if the PM domain can be powered off.
+ *
+ * @dev: Device for which the PM domain may need to stay on for.
+ * @on: Value to set or unset for the condition.
+ *
+ * For some usecases a consumer driver requires its device to remain power-on
+ * from the PM domain perspective during runtime. This function allows the
+ * behaviour to be dynamically controlled for a device attached to a genpd.
+ *
+ * It is assumed that the users guarantee that the genpd wouldn't be detached
+ * while this routine is getting called.
+ *
+ * Return: Returns 0 on success and negative error values on failures.
+ */
+int dev_pm_genpd_rpm_always_on(struct device *dev, bool on)
+{
+	struct generic_pm_domain *genpd;
+
+	genpd = dev_to_genpd_safe(dev);
+	if (!genpd)
+		return -ENODEV;
+
+	genpd_lock(genpd);
+	dev_gpd_data(dev)->rpm_always_on = on;
+	genpd_unlock(genpd);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dev_pm_genpd_rpm_always_on);
+
 static int _genpd_power_on(struct generic_pm_domain *genpd, bool timed)
 {
 	unsigned int state_idx = genpd->state_idx;
@@ -868,6 +899,10 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
 		if (!pm_runtime_suspended(pdd->dev) ||
 			irq_safe_dev_in_sleep_domain(pdd->dev, genpd))
 			not_suspended++;
+
+		/* The device may need its PM domain to stay powered on. */
+		if (to_gpd_data(pdd)->rpm_always_on)
+			return -EBUSY;
 	}
 
 	if (not_suspended > 1 || (not_suspended == 1 && !one_dev_on))

include/linux/pm_domain.h

@@ -261,6 +261,7 @@ struct generic_pm_domain_data {
 	unsigned int rpm_pstate;
 	unsigned int opp_token;
 	bool hw_mode;
+	bool rpm_always_on;
 	void *data;
 };
 
@@ -293,6 +294,7 @@ ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev);
 void dev_pm_genpd_synced_poweroff(struct device *dev);
 int dev_pm_genpd_set_hwmode(struct device *dev, bool enable);
 bool dev_pm_genpd_get_hwmode(struct device *dev);
+int dev_pm_genpd_rpm_always_on(struct device *dev, bool on);
 
 extern struct dev_power_governor simple_qos_governor;
 extern struct dev_power_governor pm_domain_always_on_gov;
@@ -376,6 +378,11 @@ static inline bool dev_pm_genpd_get_hwmode(struct device *dev)
 	return false;
 }
 
+static inline int dev_pm_genpd_rpm_always_on(struct device *dev, bool on)
+{
+	return -EOPNOTSUPP;
+}
+
 #define simple_qos_governor		(*(struct dev_power_governor *)(NULL))
 #define pm_domain_always_on_gov		(*(struct dev_power_governor *)(NULL))
 #endif