[PATCH 2/2] regulator: provide regulator_set_voltage_sel_regmap_step() helper

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>

On some devices we need to manually ramp the regulators to desired
voltage one step at a time. This patch adds a helper routine for
regmap users that checks if the regulator is enabled and, if so,
iterates over all selectors between the current one and the one
representing the targeted voltage setting.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
---
 drivers/regulator/helpers.c      | 48 ++++++++++++++++++++++++++++++++
 include/linux/regulator/driver.h |  2 ++
 2 files changed, 50 insertions(+)

diff --git a/drivers/regulator/helpers.c b/drivers/regulator/helpers.c
index 5686a1335bd3..6eb0e147bbc9 100644
--- a/drivers/regulator/helpers.c
+++ b/drivers/regulator/helpers.c
@@ -19,6 +19,8 @@
 #include <linux/regulator/driver.h>
 #include <linux/module.h>
 
+#include "internal.h"
+
 /**
  * regulator_is_enabled_regmap - standard is_enabled() for regmap users
  *
@@ -279,6 +281,52 @@ int regulator_set_voltage_sel_regmap(struct regulator_dev *rdev, unsigned sel)
 }
 EXPORT_SYMBOL_GPL(regulator_set_voltage_sel_regmap);
 
+/**
+ * regulator_set_voltage_sel_regmap_step - stepping set_voltage_sel for regmap
+ *                                         users
+ *
+ * @rdev: regulator to operate on
+ * @sel: Selector to set
+ *
+ * Regulators that use regmap for their register I/O but want to ramp up/down
+ * to the selected voltage one step at a time can use this routine as their
+ * set_voltage_sel operation.
+ */
+int regulator_set_voltage_sel_regmap_step(struct regulator_dev *rdev,
+					  unsigned int sel)
+{
+	int ret, curr, diff, i, end;
+	bool asc;
+
+	/*
+	 * If the regulator is disabled, we can program the desired
+	 * voltage right away.
+	 */
+	if (!_regulator_is_enabled(rdev))
+		return regulator_set_voltage_sel_regmap(rdev, sel);
+
+	curr = regulator_get_voltage_sel_regmap(rdev);
+	if (curr < 0)
+		return curr;
+
+	diff = curr - sel;
+	if (diff == 0)
+		return 0; /* Already there. */
+
+	asc = diff > 0 ? false : true;
+	end = asc ? sel + 1 : sel - 1;
+	asc ? curr++ : curr--;
+
+	for (i = curr; i != end; asc ? i++ : i--) {
+		ret = regulator_set_voltage_sel_regmap(rdev, i);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(regulator_set_voltage_sel_regmap_step);
+
 /**
  * regulator_map_voltage_iterate - map_voltage() based on list_voltage()
  *
diff --git a/include/linux/regulator/driver.h b/include/linux/regulator/driver.h
index a9c030192147..eedd8b495900 100644
--- a/include/linux/regulator/driver.h
+++ b/include/linux/regulator/driver.h
@@ -530,6 +530,8 @@ int regulator_set_voltage_sel_pickable_regmap(struct regulator_dev *rdev,
 						unsigned int sel);
 int regulator_get_voltage_sel_regmap(struct regulator_dev *rdev);
 int regulator_set_voltage_sel_regmap(struct regulator_dev *rdev, unsigned sel);
+int regulator_set_voltage_sel_regmap_step(struct regulator_dev *rdev,
+					  unsigned int 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);
-- 
2.19.1