Merge branch 'opp/linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm

Merge an operating performance points (OPP) framework update for
5.7-rc2 from Viresh Kumar:

"This contains a single patch that lets the OPP core to be used by
 several IO drivers without making a lot of changes in them for the
 case where the same driver may be used by a platform with an OPP
 table or a clock node on another one. I am looking to get this into
 5.7 release itself, which will enable other users (in multiple
 frameworks) to get merged without waiting for the dependency to get
 resolved."

* 'opp/linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm:
  opp: Manage empty OPP tables with clk handle

drivers/opp/core.c

@@ -819,6 +819,8 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
 	if (unlikely(!target_freq)) {
 		if (opp_table->required_opp_tables) {
 			ret = _set_required_opps(dev, opp_table, NULL);
+		} else if (!_get_opp_count(opp_table)) {
+			return 0;
 		} else {
 			dev_err(dev, "target frequency can't be 0\n");
 			ret = -EINVAL;
@@ -849,6 +851,18 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
 		goto put_opp_table;
 	}
 
+	/*
+	 * For IO devices which require an OPP on some platforms/SoCs
+	 * while just needing to scale the clock on some others
+	 * we look for empty OPP tables with just a clock handle and
+	 * scale only the clk. This makes dev_pm_opp_set_rate()
+	 * equivalent to a clk_set_rate()
+	 */
+	if (!_get_opp_count(opp_table)) {
+		ret = _generic_set_opp_clk_only(dev, clk, freq);
+		goto put_opp_table;
+	}
+
 	temp_freq = old_freq;
 	old_opp = _find_freq_ceil(opp_table, &temp_freq);
 	if (IS_ERR(old_opp)) {