pmdomain: core: Add residency reflection for domain-idlestates to debugfs

For regular cpuidle states we are reflecting over the selected/entered
state to see if the sleep-duration meets the residency for the state. The
output from the reflection is an "above" value to indicate the number of
times the state was too deep and a "below" value for the number of times it
was too shallow.

Let's implement the similar thing for genpd's domain-idlestates along with
genpd's governor and put the information in the genpd's debugfs.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20250314100103.1294715-5-ulf.hansson@linaro.org

Author: Ulf Hansson

drivers/pmdomain/core.c

@@ -304,10 +304,40 @@ static void genpd_update_accounting(struct generic_pm_domain *genpd)
 
 	genpd->accounting_time = now;
 }
+
+static void genpd_reflect_residency(struct generic_pm_domain *genpd)
+{
+	struct genpd_governor_data *gd = genpd->gd;
+	struct genpd_power_state *state, *next_state;
+	unsigned int state_idx;
+	s64 sleep_ns, target_ns;
+
+	if (!gd || !gd->reflect_residency)
+		return;
+
+	sleep_ns = ktime_to_ns(ktime_sub(ktime_get(), gd->last_enter));
+	state_idx = genpd->state_idx;
+	state = &genpd->states[state_idx];
+	target_ns = state->power_off_latency_ns + state->residency_ns;
+
+	if (sleep_ns < target_ns) {
+		state->above++;
+	} else if (state_idx < (genpd->state_count -1)) {
+		next_state = &genpd->states[state_idx + 1];
+		target_ns = next_state->power_off_latency_ns +
+			next_state->residency_ns;
+
+		if (sleep_ns >= target_ns)
+			state->below++;
+	}
+
+	gd->reflect_residency = false;
+}
 #else
 static inline void genpd_debug_add(struct generic_pm_domain *genpd) {}
 static inline void genpd_debug_remove(struct generic_pm_domain *genpd) {}
 static inline void genpd_update_accounting(struct generic_pm_domain *genpd) {}
+static inline void genpd_reflect_residency(struct generic_pm_domain *genpd) {}
 #endif
 
 static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
@@ -982,6 +1012,9 @@ static int genpd_power_on(struct generic_pm_domain *genpd, unsigned int depth)
 	if (genpd_status_on(genpd))
 		return 0;
 
+	/* Reflect over the entered idle-states residency for debugfs. */
+	genpd_reflect_residency(genpd);
+
 	/*
 	 * The list is guaranteed not to change while the loop below is being
 	 * executed, unless one of the parents' .power_on() callbacks fiddles
@@ -3517,7 +3550,7 @@ static int idle_states_show(struct seq_file *s, void *data)
 	if (ret)
 		return -ERESTARTSYS;
 
-	seq_puts(s, "State          Time Spent(ms) Usage          Rejected\n");
+	seq_puts(s, "State          Time Spent(ms) Usage      Rejected   Above      Below\n");
 
 	for (i = 0; i < genpd->state_count; i++) {
 		struct genpd_power_state *state = &genpd->states[i];
@@ -3537,9 +3570,10 @@ static int idle_states_show(struct seq_file *s, void *data)
 			snprintf(state_name, ARRAY_SIZE(state_name), "S%-13d", i);
 
 		do_div(idle_time, NSEC_PER_MSEC);
-		seq_printf(s, "%-14s %-14llu %-14llu %llu\n",
+		seq_printf(s, "%-14s %-14llu %-10llu %-10llu %-10llu %llu\n",
 			   state->name ?: state_name, idle_time,
-			   state->usage, state->rejected);
+			   state->usage, state->rejected, state->above,
+			   state->below);
 	}
 
 	genpd_unlock(genpd);

drivers/pmdomain/governor.c

@@ -392,6 +392,8 @@ static bool cpu_power_down_ok(struct dev_pm_domain *pd)
 		if (idle_duration_ns >= (genpd->states[i].residency_ns +
 		    genpd->states[i].power_off_latency_ns)) {
 			genpd->state_idx = i;
+			genpd->gd->last_enter = now;
+			genpd->gd->reflect_residency = true;
 			return true;
 		}
 	} while (--i >= 0);

include/linux/pm_domain.h

@@ -142,6 +142,8 @@ struct genpd_governor_data {
 	bool max_off_time_changed;
 	ktime_t next_wakeup;
 	ktime_t next_hrtimer;
+	ktime_t last_enter;
+	bool reflect_residency;
 	bool cached_power_down_ok;
 	bool cached_power_down_state_idx;
 };
@@ -153,6 +155,8 @@ struct genpd_power_state {
 	s64 residency_ns;
 	u64 usage;
 	u64 rejected;
+	u64 above;
+	u64 below;
 	struct fwnode_handle *fwnode;
 	u64 idle_time;
 	void *data;