PM / OPP: Add dev_pm_opp_{set|put}_clkname()

diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
index 5ee7aadf0abf..f675b83ba721 100644
--- a/drivers/base/power/opp/core.c
+++ b/drivers/base/power/opp/core.c
@@ -1363,6 +1363,96 @@  void dev_pm_opp_put_regulators(struct opp_table *opp_table)
 EXPORT_SYMBOL_GPL(dev_pm_opp_put_regulators);
 
 /**
+ * dev_pm_opp_set_clkname() - Set clk name for the device
+ * @dev: Device for which clk name is being set.
+ * @name: Clk name.
+ *
+ * In order to support OPP switching, OPP layer needs to get pointer to the
+ * clock for the device. Simple cases work fine without using this routine (i.e.
+ * by passing connection-id as NULL), but for a device with multiple clocks
+ * available, the OPP core needs to know the exact name of the clk to use.
+ *
+ * This must be called before any OPPs are initialized for the device.
+ */
+struct opp_table *dev_pm_opp_set_clkname(struct device *dev, const char *name)
+{
+	struct opp_table *opp_table;
+	int ret;
+
+	opp_table = dev_pm_opp_get_opp_table(dev);
+	if (!opp_table)
+		return ERR_PTR(-ENOMEM);
+
+	/* This should be called before OPPs are initialized */
+	if (WARN_ON(!list_empty(&opp_table->opp_list))) {
+		ret = -EBUSY;
+		goto err;
+	}
+
+	/* Already have clkname set */
+	if (opp_table->clk_name) {
+		ret = -EBUSY;
+		goto err;
+	}
+
+	opp_table->clk_name = kstrdup(name, GFP_KERNEL);
+	if (!opp_table->clk_name) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	/* Already have default clk set, free it */
+	if (!IS_ERR(opp_table->clk))
+		clk_put(opp_table->clk);
+
+	/* Find clk for the device */
+	opp_table->clk = clk_get(dev, name);
+	if (IS_ERR(opp_table->clk)) {
+		ret = PTR_ERR(opp_table->clk);
+		if (ret != -EPROBE_DEFER) {
+			dev_err(dev, "%s: Couldn't find clock: %d\n", __func__,
+				ret);
+		}
+		goto free_clk_name;
+	}
+
+	return opp_table;
+
+free_clk_name:
+	kfree(opp_table->clk_name);
+	opp_table->clk_name = NULL;
+
+err:
+	dev_pm_opp_put_opp_table(opp_table);
+
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(dev_pm_opp_set_clkname);
+
+/**
+ * dev_pm_opp_put_clkname() - Releases resources blocked for clk.
+ * @opp_table: OPP table returned from dev_pm_opp_set_clkname().
+ */
+void dev_pm_opp_put_clkname(struct opp_table *opp_table)
+{
+	if (!opp_table->clk_name) {
+		pr_err("%s: Doesn't have clk set\n", __func__);
+		return;
+	}
+
+	/* Make sure there are no concurrent readers while updating opp_table */
+	WARN_ON(!list_empty(&opp_table->opp_list));
+
+	clk_put(opp_table->clk);
+	opp_table->clk = ERR_PTR(-EINVAL);
+	kfree(opp_table->clk_name);
+	opp_table->clk_name = NULL;
+
+	dev_pm_opp_put_opp_table(opp_table);
+}
+EXPORT_SYMBOL_GPL(dev_pm_opp_put_clkname);
+
+/**
  * dev_pm_opp_register_set_opp_helper() - Register custom set OPP helper
  * @dev: Device for which the helper is getting registered.
  * @set_opp: Custom set OPP helper.
diff --git a/drivers/base/power/opp/opp.h b/drivers/base/power/opp/opp.h
index 166eef990599..0443ea4452b4 100644
--- a/drivers/base/power/opp/opp.h
+++ b/drivers/base/power/opp/opp.h
@@ -132,6 +132,7 @@  enum opp_table_access {
  * @supported_hw: Array of version number to support.
  * @supported_hw_count: Number of elements in supported_hw array.
  * @prop_name: A name to postfix to many DT properties, while parsing them.
+ * @clkname: Clock's name.
  * @clk: Device's clock handle
  * @regulators: Supply regulators
  * @regulator_count: Number of power supply regulators
@@ -167,6 +168,7 @@  struct opp_table {
 	unsigned int *supported_hw;
 	unsigned int supported_hw_count;
 	const char *prop_name;
+	const char *clk_name;
 	struct clk *clk;
 	struct regulator **regulators;
 	unsigned int regulator_count;
diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
index a6685b3dde26..51ec727b4824 100644
--- a/include/linux/pm_opp.h
+++ b/include/linux/pm_opp.h
@@ -121,6 +121,8 @@  struct opp_table *dev_pm_opp_set_prop_name(struct device *dev, const char *name)
 void dev_pm_opp_put_prop_name(struct opp_table *opp_table);
 struct opp_table *dev_pm_opp_set_regulators(struct device *dev, const char * const names[], unsigned int count);
 void dev_pm_opp_put_regulators(struct opp_table *opp_table);
+struct opp_table *dev_pm_opp_set_clkname(struct device *dev, const char * name);
+void dev_pm_opp_put_clkname(struct opp_table *opp_table);
 struct opp_table *dev_pm_opp_register_set_opp_helper(struct device *dev, int (*set_opp)(struct dev_pm_set_opp_data *data));
 void dev_pm_opp_register_put_opp_helper(struct opp_table *opp_table);
 int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq);
@@ -257,6 +259,13 @@  static inline struct opp_table *dev_pm_opp_set_regulators(struct device *dev, co
 
 static inline void dev_pm_opp_put_regulators(struct opp_table *opp_table) {}
 
+static inline struct opp_table *dev_pm_opp_set_clkname(struct device *dev, const char * name)
+{
+	return ERR_PTR(-ENOTSUPP);
+}
+
+static inline void dev_pm_opp_put_clkname(struct opp_table *opp_table) {}
+
 static inline int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
 {
 	return -ENOTSUPP;