OPP: Introduce dev_pm_opp_find_freq_ceil_by_volt()

This patch introduces a new helper routine in the OPP core, which
returns the OPP with the highest frequency which has voltage less than
or equal to the target voltage passed to the helper.
Signed-off-by: Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>
[ Viresh: Massaged the commit log and renamed the helper with some
cleanups. ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/opp/core.c

@@ -526,6 +526,60 @@ struct dev_pm_opp *dev_pm_opp_find_freq_floor(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_find_freq_floor);
 
+/**
+ * dev_pm_opp_find_freq_ceil_by_volt() - Find OPP with highest frequency for
+ *					 target voltage.
+ * @dev:	Device for which we do this operation.
+ * @u_volt:	Target voltage.
+ *
+ * Search for OPP with highest (ceil) frequency and has voltage <= u_volt.
+ *
+ * Return: matching *opp, else returns ERR_PTR in case of error which should be
+ * handled using IS_ERR.
+ *
+ * Error return values can be:
+ * EINVAL:	bad parameters
+ *
+ * The callers are required to call dev_pm_opp_put() for the returned OPP after
+ * use.
+ */
+struct dev_pm_opp *dev_pm_opp_find_freq_ceil_by_volt(struct device *dev,
+						     unsigned long u_volt)
+{
+	struct opp_table *opp_table;
+	struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);
+
+	if (!dev || !u_volt) {
+		dev_err(dev, "%s: Invalid argument volt=%lu\n", __func__,
+			u_volt);
+		return ERR_PTR(-EINVAL);
+	}
+
+	opp_table = _find_opp_table(dev);
+	if (IS_ERR(opp_table))
+		return ERR_CAST(opp_table);
+
+	mutex_lock(&opp_table->lock);
+
+	list_for_each_entry(temp_opp, &opp_table->opp_list, node) {
+		if (temp_opp->available) {
+			if (temp_opp->supplies[0].u_volt > u_volt)
+				break;
+			opp = temp_opp;
+		}
+	}
+
+	/* Increment the reference count of OPP */
+	if (!IS_ERR(opp))
+		dev_pm_opp_get(opp);
+
+	mutex_unlock(&opp_table->lock);
+	dev_pm_opp_put_opp_table(opp_table);
+
+	return opp;
+}
+EXPORT_SYMBOL_GPL(dev_pm_opp_find_freq_ceil_by_volt);
+
 static int _set_opp_voltage(struct device *dev, struct regulator *reg,
 			    struct dev_pm_opp_supply *supply)
 {

include/linux/pm_opp.h

@@ -102,6 +102,8 @@ struct dev_pm_opp *dev_pm_opp_find_freq_exact(struct device *dev,
 
 struct dev_pm_opp *dev_pm_opp_find_freq_floor(struct device *dev,
 					      unsigned long *freq);
+struct dev_pm_opp *dev_pm_opp_find_freq_ceil_by_volt(struct device *dev,
+						     unsigned long u_volt);
 
 struct dev_pm_opp *dev_pm_opp_find_freq_ceil(struct device *dev,
 					     unsigned long *freq);
@@ -207,6 +209,12 @@ static inline struct dev_pm_opp *dev_pm_opp_find_freq_floor(struct device *dev,
 	return ERR_PTR(-ENOTSUPP);
 }
 
+static inline struct dev_pm_opp *dev_pm_opp_find_freq_ceil_by_volt(struct device *dev,
+					unsigned long u_volt)
+{
+	return ERR_PTR(-ENOTSUPP);
+}
+
 static inline struct dev_pm_opp *dev_pm_opp_find_freq_ceil(struct device *dev,
 					unsigned long *freq)
 {