[PATCH v3 2/2] regulator: Allow for asymmetric settling times

[Matthias Kaehlcke]

Some regulators have different settling times for voltage increases and
decreases. To avoid a time penalty on the faster transition allow for
different settings for up- and downward transitions.

Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Acked-by: Laxman Dewangan <ldewangan@xxxxxxxxxx>
---
Changes in v3:
- Added check for conflicting settling time configurations. A warning is
  printed if up/down settling times are specified at the same time as
  the more general ("symmetrical") setting. In case of conflicts the
  up/down times are ignored and 'regulator-settling-time-us' is used.

 drivers/regulator/core.c          |  6 ++++++
 drivers/regulator/of_regulator.c  | 19 +++++++++++++++++++
 include/linux/regulator/machine.h |  6 ++++++
 3 files changed, 31 insertions(+)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index c0d9ae8d0860..919b7f178209 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -2767,6 +2767,12 @@ static int _regulator_set_voltage_time(struct regulator_dev *rdev,
 		ramp_delay = rdev->desc->ramp_delay;
 	else if (rdev->constraints->settling_time)
 		return rdev->constraints->settling_time;
+	else if (rdev->constraints->settling_time_up &&
+		 (new_uV > old_uV))
+		return rdev->constraints->settling_time_up;
+	else if (rdev->constraints->settling_time_down &&
+		 (new_uV < old_uV))
+		return rdev->constraints->settling_time_down;
 
 	if (ramp_delay == 0) {
 		rdev_dbg(rdev, "ramp_delay not set\n");
diff --git a/drivers/regulator/of_regulator.c b/drivers/regulator/of_regulator.c
index 09d677d5d3f0..96bf75458da5 100644
--- a/drivers/regulator/of_regulator.c
+++ b/drivers/regulator/of_regulator.c
@@ -90,6 +90,25 @@ static void of_get_regulation_constraints(struct device_node *np,
 	if (!ret)
 		constraints->settling_time = pval;
 
+	ret = of_property_read_u32(np, "regulator-settling-time-up-us", &pval);
+	if (!ret)
+		constraints->settling_time_up = pval;
+	if (constraints->settling_time_up && constraints->settling_time) {
+		pr_warn("%s: ambiguous configuration for settling time, ignoring 'regulator-settling-time-up-us'\n",
+			np->name);
+		constraints->settling_time_up = 0;
+	}
+
+	ret = of_property_read_u32(np, "regulator-settling-time-down-us",
+				   &pval);
+	if (!ret)
+		constraints->settling_time_down = pval;
+	if (constraints->settling_time_down && constraints->settling_time) {
+		pr_warn("%s: ambiguous configuration for settling time, ignoring 'regulator-settling-time-down-us'\n",
+			np->name);
+		constraints->settling_time_down = 0;
+	}
+
 	ret = of_property_read_u32(np, "regulator-enable-ramp-delay", &pval);
 	if (!ret)
 		constraints->enable_time = pval;
diff --git a/include/linux/regulator/machine.h b/include/linux/regulator/machine.h
index 117699d1f7df..9cd4fef37203 100644
--- a/include/linux/regulator/machine.h
+++ b/include/linux/regulator/machine.h
@@ -110,6 +110,10 @@ struct regulator_state {
  * @ramp_delay: Time to settle down after voltage change (unit: uV/us)
  * @settling_time: Time to settle down after voltage change when voltage
  *		   change is non-linear (unit: microseconds).
+ * @settling_time_up: Time to settle down after voltage increase when voltage
+ *		      change is non-linear (unit: microseconds).
+ * @settling_time_down : Time to settle down after voltage decrease when
+ *			 voltage change is non-linear (unit: microseconds).
  * @active_discharge: Enable/disable active discharge. The enum
  *		      regulator_active_discharge values are used for
  *		      initialisation.
@@ -152,6 +156,8 @@ struct regulation_constraints {
 
 	unsigned int ramp_delay;
 	unsigned int settling_time;
+	unsigned int settling_time_up;
+	unsigned int settling_time_down;
 	unsigned int enable_time;
 
 	unsigned int active_discharge;
-- 
2.13.0.303.g4ebf302169-goog