OPP: Extend support for the opp-level beyond required-opps

At this point the level (performance state) for an OPP is currently limited
to be requested for a device that is attached to a PM domain.  Moreover,
the device needs to have the so called required-opps assigned to it, which
are based upon OPP tables being described in DT.

To extend the support beyond required-opps and DT, let's enable the level
to be set for all OPPs. More precisely, if the requested OPP has a valid
level let's try to request it through the device's optional PM domain, via
calling dev_pm_domain_set_performance_state().
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
[ Viresh: Handle NULL opp in _set_opp_level() ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/opp/core.c

@@ -1107,6 +1107,28 @@ void _update_set_required_opps(struct opp_table *opp_table)
 		opp_table->set_required_opps = _opp_set_required_opps_generic;
 }
 
+static int _set_opp_level(struct device *dev, struct opp_table *opp_table,
+			  struct dev_pm_opp *opp)
+{
+	unsigned int level = 0;
+	int ret = 0;
+
+	if (opp) {
+		if (!opp->level)
+			return 0;
+
+		level = opp->level;
+	}
+
+	/* Request a new performance state through the device's PM domain. */
+	ret = dev_pm_domain_set_performance_state(dev, level);
+	if (ret)
+		dev_err(dev, "Failed to set performance state %u (%d)\n", level,
+			ret);
+
+	return ret;
+}
+
 static void _find_current_opp(struct device *dev, struct opp_table *opp_table)
 {
 	struct dev_pm_opp *opp = ERR_PTR(-ENODEV);
@@ -1154,8 +1176,13 @@ static int _disable_opp_table(struct device *dev, struct opp_table *opp_table)
 	if (opp_table->regulators)
 		regulator_disable(opp_table->regulators[0]);
 
+	ret = _set_opp_level(dev, opp_table, NULL);
+	if (ret)
+		goto out;
+
 	ret = _set_required_opps(dev, opp_table, NULL, false);
 
+out:
 	opp_table->enabled = false;
 	return ret;
 }
@@ -1198,6 +1225,10 @@ static int _set_opp(struct device *dev, struct opp_table *opp_table,
 			return ret;
 		}
 
+		ret = _set_opp_level(dev, opp_table, opp);
+		if (ret)
+			return ret;
+
 		ret = _set_opp_bw(opp_table, opp, dev);
 		if (ret) {
 			dev_err(dev, "Failed to set bw: %d\n", ret);
@@ -1241,6 +1272,10 @@ static int _set_opp(struct device *dev, struct opp_table *opp_table,
 			return ret;
 		}
 
+		ret = _set_opp_level(dev, opp_table, opp);
+		if (ret)
+			return ret;
+
 		ret = _set_required_opps(dev, opp_table, opp, false);
 		if (ret) {
 			dev_err(dev, "Failed to set required opps: %d\n", ret);