regulator: core: Allow drivers to set simple linear voltage maps as data

A lot of regulator hardware maps selectors on to voltages with a simple
linear mapping function

    selector = base + (selector * step size)

Provide off the shelf list_voltage() and map_voltage() operations which
use new min_uV and uV_step members in the regulator_desc to implement
this function.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>

drivers/regulator/core.c

@@ -1859,6 +1859,26 @@ int regulator_count_voltages(struct regulator *regulator)
 }
 EXPORT_SYMBOL_GPL(regulator_count_voltages);
 
+/**
+ * regulator_list_voltage_linear - List voltages with simple calculation
+ *
+ * @rdev: Regulator device
+ * @selector: Selector to convert into a voltage
+ *
+ * Regulators with a simple linear mapping between voltages and
+ * selectors can set min_uV and uV_step in the regulator descriptor
+ * and then use this function as their list_voltage() operation,
+ */
+int regulator_list_voltage_linear(struct regulator_dev *rdev,
+				  unsigned int selector)
+{
+	if (selector >= rdev->desc->n_voltages)
+		return -EINVAL;
+
+	return rdev->desc->min_uV + (rdev->desc->uV_step * selector);
+}
+EXPORT_SYMBOL_GPL(regulator_list_voltage_linear);
+
 /**
  * regulator_list_voltage - enumerate supported voltages
  * @regulator: regulator source
@@ -2007,6 +2027,39 @@ int regulator_map_voltage_iterate(struct regulator_dev *rdev,
 }
 EXPORT_SYMBOL_GPL(regulator_map_voltage_iterate);
 
+/**
+ * regulator_map_voltage_linear - map_voltage() for simple linear mappings
+ *
+ * @rdev: Regulator to operate on
+ * @min_uV: Lower bound for voltage
+ * @max_uV: Upper bound for voltage
+ *
+ * Drivers providing min_uV and uV_step in their regulator_desc can
+ * use this as their map_voltage() operation.
+ */
+int regulator_map_voltage_linear(struct regulator_dev *rdev,
+				 int min_uV, int max_uV)
+{
+	int ret, voltage;
+
+	if (!rdev->desc->uV_step) {
+		BUG_ON(!rdev->desc->uV_step);
+		return -EINVAL;
+	}
+
+	ret = (min_uV - rdev->desc->min_uV) / rdev->desc->uV_step;
+	if (ret < 0)
+		return ret;
+
+	/* Map back into a voltage to verify we're still in bounds */
+	voltage = rdev->desc->ops->list_voltage(rdev, ret);
+	if (voltage < min_uV || voltage > max_uV)
+		return -EINVAL;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(regulator_map_voltage_linear);
+
 static int _regulator_do_set_voltage(struct regulator_dev *rdev,
 				     int min_uV, int max_uV)
 {

include/linux/regulator/driver.h

@@ -161,12 +161,16 @@ enum regulator_type {
  * @name: Identifying name for the regulator.
  * @supply_name: Identifying the regulator supply
  * @id: Numerical identifier for the regulator.
- * @n_voltages: Number of selectors available for ops.list_voltage().
  * @ops: Regulator operations table.
  * @irq: Interrupt number for the regulator.
  * @type: Indicates if the regulator is a voltage or current regulator.
  * @owner: Module providing the regulator, used for refcounting.
-
+ *
+ * @n_voltages: Number of selectors available for ops.list_voltage().
+ *
+ * @min_uV: Voltage given by the lowest selector (if linear mapping)
+ * @uV_step: Voltage increase with each selector (if linear mapping)
+ *
  * @vsel_reg: Register for selector when using regulator_regmap_X_voltage_
  * @vsel_mask: Mask for register bitfield used for selector
  * @enable_reg: Register for control when using regmap enable/disable ops
@@ -182,6 +186,9 @@ struct regulator_desc {
 	enum regulator_type type;
 	struct module *owner;
 
+	unsigned int min_uV;
+	unsigned int uV_step;
+
 	unsigned int vsel_reg;
 	unsigned int vsel_mask;
 	unsigned int enable_reg;
@@ -262,6 +269,10 @@ int rdev_get_id(struct regulator_dev *rdev);
 
 int regulator_mode_to_status(unsigned int);
 
+int regulator_list_voltage_linear(struct regulator_dev *rdev,
+				  unsigned int selector);
+int regulator_map_voltage_linear(struct regulator_dev *rdev,
+				  int min_uV, int max_uV);
 int regulator_map_voltage_iterate(struct regulator_dev *rdev,
 				  int min_uV, int max_uV);
 int regulator_get_voltage_sel_regmap(struct regulator_dev *rdev);