regulator: Allow regulators to verify enabled during enable()

Some regulators might need to verify that they have indeed been enabled
after the enable() call is made and enable_time delay has passed.

This is implemented by repeatedly checking is_enabled() upto
poll_enabled_time, waiting for the already calculated enable delay in
each iteration.

Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Change-Id: I8f0c9f6aaa1be5373628b1bcd77dbd6a53c65d0e

---
v3: addressed minor review comments, improved kernel doc
v2: Address review comments, including swapping enable_time and poll_enabled_time.

2 files changed, 67 insertions, 1 deletions

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 03154f5b939f..538a2779986a 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -2347,6 +2347,37 @@ static void _regulator_enable_delay(unsigned int delay)
 		udelay(us);
 }
 
+/**
+ * _regulator_check_status_enabled
+ *
+ * A helper function to check if the regulator status can be interpreted
+ * as 'regulator is enabled'.
+ * @rdev: the regulator device to check
+ *
+ * Return:
+ * * 1			- if status shows regulator is in enabled state
+ * * 0			- if not enabled state
+ * * Error Value	- as received from ops->get_status()
+ */
+static inline int _regulator_check_status_enabled(struct regulator_dev *rdev)
+{
+	int ret = rdev->desc->ops->get_status(rdev);
+
+	if (ret < 0) {
+		rdev_info(rdev, "get_status returned error: %d\n", ret);
+		return ret;
+	}
+
+	switch (ret) {
+	case REGULATOR_STATUS_OFF:
+	case REGULATOR_STATUS_ERROR:
+	case REGULATOR_STATUS_UNDEFINED:
+		return 0;
+	default:
+		return 1;
+	}
+}
+
 static int _regulator_do_enable(struct regulator_dev *rdev)
 {
 	int ret, delay;
@@ -2407,7 +2438,37 @@ static int _regulator_do_enable(struct regulator_dev *rdev)
 	 * together.  */
 	trace_regulator_enable_delay(rdev_get_name(rdev));
 
-	_regulator_enable_delay(delay);
+	/* If poll_enabled_time is set, poll upto the delay calculated
+	 * above, delaying poll_enabled_time uS to check if the regulator
+	 * actually got enabled.
+	 * If the regulator isn't enabled after enable_delay has
+	 * expired, return -ETIMEDOUT.
+	 */
+	if (rdev->desc->poll_enabled_time) {
+		unsigned int time_remaining = delay;
+
+		while (time_remaining > 0) {
+			_regulator_enable_delay(rdev->desc->poll_enabled_time);
+
+			if (rdev->desc->ops->get_status) {
+				ret = _regulator_check_status_enabled(rdev);
+				if (ret < 0)
+					return ret;
+				else if (ret)
+					break;
+			} else if (rdev->desc->ops->is_enabled(rdev))
+				break;
+
+			time_remaining -= rdev->desc->poll_enabled_time;
+		}
+
+		if (time_remaining <= 0) {
+			rdev_err(rdev, "Enabled check timed out\n");
+			return -ETIMEDOUT;
+		}
+	} else {
+		_regulator_enable_delay(delay);
+	}
 
 	trace_regulator_enable_complete(rdev_get_name(rdev));
 
diff --git a/include/linux/regulator/driver.h b/include/linux/regulator/driver.h
index 7eb9fea8e482..436df3ba0b2a 100644
--- a/include/linux/regulator/driver.h
+++ b/include/linux/regulator/driver.h
@@ -305,6 +305,9 @@ enum regulator_type {
  * @enable_time: Time taken for initial enable of regulator (in uS).
  * @off_on_delay: guard time (in uS), before re-enabling a regulator
  *
+ * @poll_enabled_time: The polling interval (in uS) to use while checking that
+ *                     the regulator was actually enabled. Max upto enable_time.
+ *
  * @of_map_mode: Maps a hardware mode defined in a DeviceTree to a standard mode
  */
 struct regulator_desc {
@@ -372,6 +375,8 @@ struct regulator_desc {
 
 	unsigned int off_on_delay;
 
+	unsigned int poll_enabled_time;
+
 	unsigned int (*of_map_mode)(unsigned int mode);
 };