[PATCH v4 3/4] opp: Add dev_pm_opp_set_voltage()

[Dmitry Osipenko <digetx@gmail.com>]

Add dev_pm_opp_set_voltage() which allows OPP table users to set voltage
in accordance to a given OPP. In particular this is needed for driving
voltage of a generic power domain which uses OPPs and doesn't have a
clock.

Tested-by: Peter Geis <pgwipeout@gmail.com>
Tested-by: Nicolas Chauvet <kwizart@gmail.com>
Tested-by: Matt Merhar <mattmerhar@protonmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/opp/core.c     | 51 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/pm_opp.h |  6 +++++
 2 files changed, 57 insertions(+)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 43e62e0e3d5b..08d205a55c07 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -2700,3 +2700,54 @@ int dev_pm_opp_sync_regulators(struct device *dev)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_sync_regulators);
+
+/**
+ * dev_pm_opp_set_voltage() - Change voltage of regulators
+ * @dev:	device for which we do this operation
+ * @opp:	opp based on which the voltages are to be configured
+ *
+ * Change voltage of the OPP table regulators.
+ *
+ * Return: 0 on success or a negative error value.
+ */
+int dev_pm_opp_set_voltage(struct device *dev, struct dev_pm_opp *opp)
+{
+	struct opp_table *opp_table;
+	struct regulator *reg;
+	int ret = 0;
+
+	/* Device may not have OPP table */
+	opp_table = _find_opp_table(dev);
+	if (IS_ERR(opp_table))
+		return 0;
+
+	/* Regulator may not be required for the device */
+	if (!opp_table->regulators)
+		goto put_table;
+
+	/* This function only supports single regulator per device */
+	if (WARN_ON(opp_table->regulator_count > 1)) {
+		dev_err(dev, "multiple regulators are not supported\n");
+		ret = -EINVAL;
+		goto put_table;
+	}
+
+	reg = opp_table->regulators[0];
+	ret = _set_opp_voltage(dev, reg, opp->supplies);
+
+	if (!opp_table->enabled) {
+		ret = regulator_enable(reg);
+		if (ret < 0) {
+			dev_warn(dev, "Failed to enable regulator: %d", ret);
+			goto put_table;
+		}
+
+		opp_table->enabled = true;
+	}
+put_table:
+	/* Drop reference taken by _find_opp_table() */
+	dev_pm_opp_put_opp_table(opp_table);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_opp_set_voltage);
diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
index 80cdb9af8268..d8f412dfc03a 100644
--- a/include/linux/pm_opp.h
+++ b/include/linux/pm_opp.h
@@ -164,6 +164,7 @@ int dev_pm_opp_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
 void dev_pm_opp_remove_table(struct device *dev);
 void dev_pm_opp_cpumask_remove_table(const struct cpumask *cpumask);
 int dev_pm_opp_sync_regulators(struct device *dev);
+int dev_pm_opp_set_voltage(struct device *dev, struct dev_pm_opp *opp);
 #else
 static inline struct opp_table *dev_pm_opp_get_opp_table(struct device *dev)
 {
@@ -405,6 +406,11 @@ static inline int dev_pm_opp_sync_regulators(struct device *dev)
 	return -ENOTSUPP;
 }
 
+static inline int dev_pm_opp_set_voltage(struct device *dev, struct dev_pm_opp *opp)
+{
+	return -ENOTSUPP;
+}
+
 #endif		/* CONFIG_PM_OPP */
 
 #if defined(CONFIG_PM_OPP) && defined(CONFIG_OF)
-- 
2.29.2