pmdomain: core: Add genpd helper to correct the usage/rejected counters

In the cpuidle-psci-domain case the ->power_off() callback is usually
returning zero to indicate success. This is because the actual call to the
PSCI FW to enter the selected domain-idlestate, needs to be done after the
->power_off() callback has returned.

When the call to the PSCI FW fails, this leads to receiving an incorrect
tracking of the usage/rejected counts for the selected domain-idlestate.
In other words, the presented debug-statistics for genpd may look better
than what the actually are.

To allow a better correctness of the data, let's add a new genpd helper
function, which enables the caller adjust the usage/rejected counters for a
domain-idlestate, in cases of errors during power-off.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20250314100103.1294715-2-ulf.hansson@linaro.org

Author: Ulf Hansson

drivers/pmdomain/core.c

@@ -728,6 +728,31 @@ int dev_pm_genpd_rpm_always_on(struct device *dev, bool on)
 }
 EXPORT_SYMBOL_GPL(dev_pm_genpd_rpm_always_on);
 
+/**
+ * pm_genpd_inc_rejected() - Adjust the rejected/usage counts for an idle-state.
+ *
+ * @genpd: The PM domain the idle-state belongs to.
+ * @state_idx: The index of the idle-state that failed.
+ *
+ * In some special cases the ->power_off() callback is asynchronously powering
+ * off the PM domain, leading to that it may return zero to indicate success,
+ * even though the actual power-off could fail. To account for this correctly in
+ * the rejected/usage counts for the idle-state statistics, users can call this
+ * function to adjust the values.
+ *
+ * It is assumed that the users guarantee that the genpd doesn't get removed
+ * while this routine is getting called.
+ */
+void pm_genpd_inc_rejected(struct generic_pm_domain *genpd,
+			   unsigned int state_idx)
+{
+	genpd_lock(genpd);
+	genpd->states[genpd->state_idx].rejected++;
+	genpd->states[genpd->state_idx].usage--;
+	genpd_unlock(genpd);
+}
+EXPORT_SYMBOL_GPL(pm_genpd_inc_rejected);
+
 static int _genpd_power_on(struct generic_pm_domain *genpd, bool timed)
 {
 	unsigned int state_idx = genpd->state_idx;

include/linux/pm_domain.h

@@ -285,6 +285,8 @@ int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd,
 int pm_genpd_init(struct generic_pm_domain *genpd,
 		  struct dev_power_governor *gov, bool is_off);
 int pm_genpd_remove(struct generic_pm_domain *genpd);
+void pm_genpd_inc_rejected(struct generic_pm_domain *genpd,
+			   unsigned int state_idx);
 struct device *dev_to_genpd_dev(struct device *dev);
 int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state);
 int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb);
@@ -336,6 +338,10 @@ static inline int pm_genpd_remove(struct generic_pm_domain *genpd)
 	return -EOPNOTSUPP;
 }
 
+static inline void pm_genpd_inc_rejected(struct generic_pm_domain *genpd,
+					 unsigned int state_idx)
+{ }
+
 static inline struct device *dev_to_genpd_dev(struct device *dev)
 {
 	return ERR_PTR(-EOPNOTSUPP);