[PATCH RFC 1/4] OPP: Add and export helper to update voltage

[Sibi Sankar <sibis@xxxxxxxxxxxxxx>]

Add and export 'dev_pm_opp_update_voltage' to find and update voltage
of an opp for a given frequency. This will be useful to update the opps
with voltages read back from firmware.

Signed-off-by: Sibi Sankar <sibis@xxxxxxxxxxxxxx>
---
 drivers/opp/core.c     | 52 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/pm_opp.h | 10 ++++++++
 2 files changed, 62 insertions(+)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 68551d6366e6b..c85c04dc2c7de 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -2197,6 +2197,58 @@ int dev_pm_opp_disable(struct device *dev, unsigned long freq)
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_disable);
 
+/**
+ * dev_pm_opp_update_voltage() - Find and update voltage
+ * @dev:	device for which we do this operation
+ * @freq:	OPP frequency to update voltage
+ * @u_volt:	voltage requested for this opp
+ *
+ * Find and update voltage of a disabled opp corresponding to the given
+ * frequency. This is useful only for devices with single power supply.
+ *
+ * Return: 0 if no modification was done OR modification was
+ * successful or a negative error value.
+ */
+int dev_pm_opp_update_voltage(struct device *dev, unsigned long freq,
+			      unsigned long u_volt)
+{
+	struct dev_pm_opp *opp = ERR_PTR(-ENODEV);
+	struct opp_table *opp_table;
+	unsigned long tol;
+	int ret = 0;
+
+	opp = dev_pm_opp_find_freq_exact(dev, freq, false);
+	if (IS_ERR(opp))
+		return PTR_ERR(opp);
+
+	/* Find the opp_table */
+	opp_table = _find_opp_table(dev);
+	if (IS_ERR(opp_table)) {
+		ret = PTR_ERR(opp_table);
+		dev_err(dev, "%s: OPP table not found (%d)\n", __func__, ret);
+		goto put_opp;
+	}
+
+	mutex_lock(&opp_table->lock);
+
+	/* update only if the opp is disabled */
+	if (opp->available)
+		goto unlock;
+
+	tol = u_volt * opp_table->voltage_tolerance_v1 / 100;
+	opp->supplies[0].u_volt_min = u_volt - tol;
+	opp->supplies[0].u_volt = u_volt;
+	opp->supplies[0].u_volt_min = u_volt + tol;
+
+unlock:
+	mutex_unlock(&opp_table->lock);
+	dev_pm_opp_put_opp_table(opp_table);
+put_opp:
+	dev_pm_opp_put(opp);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_opp_update_voltage);
+
 /**
  * dev_pm_opp_register_notifier() - Register OPP notifier for the device
  * @dev:	Device for which notifier needs to be registered
diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
index 87fa09d93d8c2..a17c462974851 100644
--- a/include/linux/pm_opp.h
+++ b/include/linux/pm_opp.h
@@ -130,6 +130,9 @@ int dev_pm_opp_enable(struct device *dev, unsigned long freq);
 
 int dev_pm_opp_disable(struct device *dev, unsigned long freq);
 
+int dev_pm_opp_update_voltage(struct device *dev, unsigned long freq,
+			      unsigned long u_volt);
+
 int dev_pm_opp_register_notifier(struct device *dev, struct notifier_block *nb);
 int dev_pm_opp_unregister_notifier(struct device *dev, struct notifier_block *nb);
 
@@ -261,6 +264,13 @@ static inline int dev_pm_opp_disable(struct device *dev, unsigned long freq)
 	return 0;
 }
 
+static inline int dev_pm_opp_update_voltage(struct device *dev,
+					    unsigned long freq,
+					    unsigned long u_volt)
+{
+	return 0;
+}
+
 static inline int dev_pm_opp_register_notifier(struct device *dev, struct notifier_block *nb)
 {
 	return -ENOTSUPP;
-- 
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