[PATCH 4/4] PM / Domains: Propagate performance state updates

[Viresh Kumar]

This commit updates genpd core to start propagating performance state
updates to master domains that have their set_performance_state()
callback set.

A genpd handles two type of performance states now. The first one is the
performance state requirement put on the genpd by the devices and
sub-domains under it, which is already represented by
genpd->performance_state. The second type, introduced in this commit, is
the performance state requirement(s) put by the genpd on its master
domain(s). There is a separate value required for each master that the
genpd has and so a new field is added to the struct gpd_link
(link->performance_state), which represents the link between a genpd and
its master. The struct gpd_link also got another field
prev_performance_state, which is used by genpd core as a temporary
variable during transitions.

We need to propagate setting performance state while powering-on a genpd
as well, as we ignore performance state requirements from sub-domains
which are powered-off. For this reason _genpd_power_on() also received
the additional parameter, depth, which is used for hierarchical locking
within genpd.

Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
 drivers/base/power/domain.c | 107 +++++++++++++++++++++++++++++-------
 include/linux/pm_domain.h   |   4 ++
 2 files changed, 92 insertions(+), 19 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 6d2e9b3406f1..81e02c5f753f 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -239,28 +239,86 @@ static void genpd_update_accounting(struct generic_pm_domain *genpd)
 static inline void genpd_update_accounting(struct generic_pm_domain *genpd) {}
 #endif
 
+static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
+					   unsigned int state, int depth);
+
 static int _genpd_set_performance_state(struct generic_pm_domain *genpd,
-					unsigned int state)
+					unsigned int state, int depth)
 {
+	struct generic_pm_domain *master;
+	struct gpd_link *link;
+	unsigned int mstate;
 	int ret;
 
 	if (!genpd_status_on(genpd))
 		goto out;
 
+	/* Propagate to masters of genpd */
+	list_for_each_entry(link, &genpd->slave_links, slave_node) {
+		master = link->master;
+
+		if (!master->set_performance_state)
+			continue;
+
+		/* Find master's performance state */
+		mstate = dev_pm_opp_xlate_performance_state(genpd->opp_table,
+				master->opp_table, state);
+		if (unlikely(!mstate))
+			goto err;
+
+		genpd_lock_nested(master, depth + 1);
+
+		link->prev_performance_state = link->performance_state;
+		link->performance_state = mstate;
+		ret = _genpd_reeval_performance_state(master, mstate, depth + 1);
+		if (ret)
+			link->performance_state = link->prev_performance_state;
+
+		genpd_unlock(master);
+
+		if (ret)
+			goto err;
+	}
+
 	ret = genpd->set_performance_state(genpd, state);
 	if (ret)
-		return ret;
+		goto err;
 
 out:
 	genpd->performance_state = state;
 	return 0;
+
+err:
+	/* Encountered an error, lets rollback */
+	list_for_each_entry_continue_reverse(link, &genpd->slave_links,
+					     slave_node) {
+		master = link->master;
+
+		if (!master->set_performance_state)
+			continue;
+
+		genpd_lock_nested(master, depth + 1);
+
+		mstate = link->prev_performance_state;
+		link->performance_state = mstate;
+
+		if (_genpd_reeval_performance_state(master, mstate, depth + 1)) {
+			pr_err("%s: Failed to roll back to %d performance state\n",
+			       master->name, mstate);
+		}
+
+		genpd_unlock(master);
+	}
+
+	return ret;
 }
 
 static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
-					   unsigned int state)
+					   unsigned int state, int depth)
 {
 	struct generic_pm_domain_data *pd_data;
 	struct pm_domain_data *pdd;
+	struct gpd_link *link;
 
 	/* New requested state is same as Max requested state */
 	if (state == genpd->performance_state)
@@ -278,21 +336,30 @@ static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
 			state = pd_data->performance_state;
 	}
 
-	if (state == genpd->performance_state)
-		return 0;
-
 	/*
-	 * We aren't propagating performance state changes of a subdomain to its
-	 * masters as we don't have hardware that needs it. Over that, the
-	 * performance states of subdomain and its masters may not have
-	 * one-to-one mapping and would require additional information. We can
-	 * get back to this once we have hardware that needs it. For that
-	 * reason, we don't have to consider performance state of the subdomains
-	 * of genpd here.
+	 * Traverse all powered-on subdomains within the domain. This can be
+	 * done without any additional locking as the link->performance_state
+	 * field is protected by the master genpd->lock, which is already taken.
+	 *
+	 * Also note that link->performance_state (subdomain's performance state
+	 * requirement to master domain) is different from
+	 * link->slave->performance_state (current performance state requirement
+	 * of the devices/sub-domains of the subdomain) and so can have a
+	 * different value.
 	 */
+	list_for_each_entry(link, &genpd->master_links, master_node) {
+		if (!genpd_status_on(link->slave))
+			continue;
+
+		if (link->performance_state > state)
+			state = link->performance_state;
+	}
+
+	if (state == genpd->performance_state)
+		return 0;
 
 update_state:
-	return _genpd_set_performance_state(genpd, state);
+	return _genpd_set_performance_state(genpd, state, depth);
 }
 
 /**
@@ -336,7 +403,7 @@ int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state)
 	prev = gpd_data->performance_state;
 	gpd_data->performance_state = state;
 
-	ret = _genpd_reeval_performance_state(genpd, state);
+	ret = _genpd_reeval_performance_state(genpd, state, 0);
 	if (ret)
 		gpd_data->performance_state = prev;
 
@@ -346,7 +413,8 @@ int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state)
 }
 EXPORT_SYMBOL_GPL(dev_pm_genpd_set_performance_state);
 
-static int _genpd_power_on(struct generic_pm_domain *genpd, bool timed)
+static int
+_genpd_power_on(struct generic_pm_domain *genpd, bool timed, int depth)
 {
 	unsigned int state_idx = genpd->state_idx;
 	ktime_t time_start;
@@ -367,7 +435,8 @@ static int _genpd_power_on(struct generic_pm_domain *genpd, bool timed)
 	elapsed_ns = ktime_to_ns(ktime_sub(ktime_get(), time_start));
 
 	if (unlikely(genpd->set_performance_state)) {
-		ret = genpd->set_performance_state(genpd, genpd->performance_state);
+		ret = _genpd_set_performance_state(genpd,
+					genpd->performance_state, depth);
 		if (ret) {
 			pr_warn("%s: Failed to set performance state %d (%d)\n",
 				genpd->name, genpd->performance_state, ret);
@@ -557,7 +626,7 @@ static int genpd_power_on(struct generic_pm_domain *genpd, unsigned int depth)
 		}
 	}
 
-	ret = _genpd_power_on(genpd, true);
+	ret = _genpd_power_on(genpd, true, depth);
 	if (ret)
 		goto err;
 
@@ -962,7 +1031,7 @@ static void genpd_sync_power_on(struct generic_pm_domain *genpd, bool use_lock,
 			genpd_unlock(link->master);
 	}
 
-	_genpd_power_on(genpd, false);
+	_genpd_power_on(genpd, false, depth);
 
 	genpd->status = GPD_STATE_ACTIVE;
 }
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 9ad101362aef..dd364abb649a 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -136,6 +136,10 @@ struct gpd_link {
 	struct list_head master_node;
 	struct generic_pm_domain *slave;
 	struct list_head slave_node;
+
+	/* Sub-domain's per-master domain performance state */
+	unsigned int performance_state;
+	unsigned int prev_performance_state;
 };
 
 struct gpd_timing_data {
-- 
2.19.1.568.g152ad8e3369a