regulator: core: Add regulator_set_voltage_time_sel to calculate ramp delay.

This patch adds regulator_set_voltage_time_sel(), to move into core, the
commonly used code by drivers to provide the .set_voltage_time_sel callback.
It will also allow us to configure different ramp delay for different
regulators easily.

Signed-off-by: Yadwinder Singh Brar <yadi.brar@samsung.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/regulator/core.c

@@ -2279,6 +2279,30 @@ int regulator_set_voltage_time(struct regulator *regulator,
 }
 EXPORT_SYMBOL_GPL(regulator_set_voltage_time);
 
+/**
+ *regulator_set_voltage_time_sel - get raise/fall time
+ * @regulator: regulator source
+ * @old_selector: selector for starting voltage
+ * @new_selector: selector for target voltage
+ *
+ * Provided with the starting and target voltage selectors, this function
+ * returns time in microseconds required to rise or fall to this new voltage
+ *
+ * Drivers providing uV_step in their regulator_desc and ramp_delay in
+ * regulation_constraints can use this as their set_voltage_time_sel()
+ * operation.
+ */
+int regulator_set_voltage_time_sel(struct regulator_dev *rdev,
+				   unsigned int old_selector,
+				   unsigned int new_selector)
+{
+	if (rdev->desc->ramp_delay && rdev->desc->uV_step)
+		return DIV_ROUND_UP(rdev->desc->uV_step *
+			abs(new_selector - old_selector),
+			rdev->desc->ramp_delay) * 1000;
+	return 0;
+}
+
 /**
  * regulator_sync_voltage - re-apply last regulator output voltage
  * @regulator: regulator source

include/linux/regulator/driver.h

@@ -170,6 +170,7 @@ enum regulator_type {
  *
  * @min_uV: Voltage given by the lowest selector (if linear mapping)
  * @uV_step: Voltage increase with each selector (if linear mapping)
+ * @ramp_delay: Time to settle down after voltage change (unit: mV/us)
  * @volt_table: Voltage mapping table (if table based mapping)
  *
  * @vsel_reg: Register for selector when using regulator_regmap_X_voltage_
@@ -189,6 +190,7 @@ struct regulator_desc {
 
 	unsigned int min_uV;
 	unsigned int uV_step;
+	unsigned int ramp_delay;
 
 	const unsigned int *volt_table;
 
@@ -285,6 +287,9 @@ int regulator_set_voltage_sel_regmap(struct regulator_dev *rdev, unsigned sel);
 int regulator_is_enabled_regmap(struct regulator_dev *rdev);
 int regulator_enable_regmap(struct regulator_dev *rdev);
 int regulator_disable_regmap(struct regulator_dev *rdev);
+int regulator_set_voltage_time_sel(struct regulator_dev *rdev,
+				   unsigned int old_selector,
+				   unsigned int new_selector);
 
 void *regulator_get_init_drvdata(struct regulator_init_data *reg_init_data);