opp: Not all power-domains are scalable

A device may have multiple power-domains and not all of them may be
scalable (i.e. support performance states). But
dev_pm_opp_attach_genpd() doesn't take that into account currently.

Fix that by not verifying the names argument with "power-domain-names"
DT property and finding the index into the required-opps array. The
names argument will anyway get verified later on when we call
dev_pm_domain_attach_by_name().

Fixes: 6319aee1 ("opp: Attach genpds to devices from within OPP core")
Reported-by: Rajendra Nayak <rnayak@codeaurora.org>
Tested-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/opp/core.c

@@ -1784,12 +1784,15 @@ static void _opp_detach_genpd(struct opp_table *opp_table)
  *
  * This helper needs to be called once with a list of all genpd to attach.
  * Otherwise the original device structure will be used instead by the OPP core.
+ *
+ * The order of entries in the names array must match the order in which
+ * "required-opps" are added in DT.
  */
 struct opp_table *dev_pm_opp_attach_genpd(struct device *dev, const char **names)
 {
 	struct opp_table *opp_table;
 	struct device *virt_dev;
-	int index, ret = -EINVAL;
+	int index = 0, ret = -EINVAL;
 	const char **name = names;
 
 	opp_table = dev_pm_opp_get_opp_table(dev);
@@ -1815,14 +1818,6 @@ struct opp_table *dev_pm_opp_attach_genpd(struct device *dev, const char **names
 		goto unlock;
 
 	while (*name) {
-		index = of_property_match_string(dev->of_node,
-						 "power-domain-names", *name);
-		if (index < 0) {
-			dev_err(dev, "Failed to find power domain: %s (%d)\n",
-				*name, index);
-			goto err;
-		}
-
 		if (index >= opp_table->required_opp_count) {
 			dev_err(dev, "Index can't be greater than required-opp-count - 1, %s (%d : %d)\n",
 				*name, opp_table->required_opp_count, index);
@@ -1843,6 +1838,7 @@ struct opp_table *dev_pm_opp_attach_genpd(struct device *dev, const char **names
 		}
 
 		opp_table->genpd_virt_devs[index] = virt_dev;
+		index++;
 		name++;
 	}