regulator: add set_voltage_time_sel infrastructure

This makes it possible to set the stabilization time for voltage
regulators in the same manner as enable_time(). The interface
only supports regulators that implements fixed selectors.

Cc: Bengt Jonsson <bengt.g.jonsson@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>
diff --git a/include/linux/regulator/driver.h b/include/linux/regulator/driver.h
index b8ed16a..6c433b8 100644
--- a/include/linux/regulator/driver.h
+++ b/include/linux/regulator/driver.h
@@ -63,7 +63,11 @@
  *                    when running with the specified parameters.
  *
  * @enable_time: Time taken for the regulator voltage output voltage to
- *               stabalise after being enabled, in microseconds.
+ *               stabilise after being enabled, in microseconds.
+ * @set_voltage_time_sel: Time taken for the regulator voltage output voltage
+ *               to stabilise after being set to a new value, in microseconds.
+ *               The function provides the from and to voltage selector, the
+ *               function should return the worst case.
  *
  * @set_suspend_voltage: Set the voltage for the regulator when the system
  *                       is suspended.
@@ -103,8 +107,11 @@
 	int (*set_mode) (struct regulator_dev *, unsigned int mode);
 	unsigned int (*get_mode) (struct regulator_dev *);
 
-	/* Time taken to enable the regulator */
+	/* Time taken to enable or set voltage on the regulator */
 	int (*enable_time) (struct regulator_dev *);
+	int (*set_voltage_time_sel) (struct regulator_dev *,
+				     unsigned int old_selector,
+				     unsigned int new_selector);
 
 	/* report regulator status ... most other accessors report
 	 * control inputs, this reports results of combining inputs