regulator: core: Add support for disabling ramp delay

Some hardwares support disabling ramp delay, so adding ramp_disable flag to
constraints. It will be used to figure out whether ramp_delay in constraints
is explicitly set to zero or its unintialized (zero by default).
And we don't need to call set_voltage_time_sel() for regulators for whom ramp
delay is disabled in constraints.

Signed-off-by: Yadwinder Singh Brar <yadi.brar@samsung.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

Documentation/devicetree/bindings/regulator/regulator.txt

@@ -12,6 +12,8 @@ Optional properties:
 - regulator-allow-bypass: allow the regulator to go into bypass mode
 - <name>-supply: phandle to the parent supply/regulator node
 - regulator-ramp-delay: ramp delay for regulator(in uV/uS)
+  For hardwares which support disabling ramp rate, it should be explicitly
+  intialised to zero (regulator-ramp-delay = <0>) for disabling ramp delay.
 
 Deprecated properties:
 - regulator-compatible: If a regulator chip contains multiple

drivers/regulator/core.c

@@ -984,7 +984,8 @@ static int set_machine_constraints(struct regulator_dev *rdev,
 		}
 	}
 
-	if (rdev->constraints->ramp_delay && ops->set_ramp_delay) {
+	if ((rdev->constraints->ramp_delay || rdev->constraints->ramp_disable)
+		&& ops->set_ramp_delay) {
 		ret = ops->set_ramp_delay(rdev, rdev->constraints->ramp_delay);
 		if (ret < 0) {
 			rdev_err(rdev, "failed to set ramp_delay\n");
@@ -2438,7 +2439,8 @@ static int _regulator_do_set_voltage(struct regulator_dev *rdev,
 	}
 
 	/* Call set_voltage_time_sel if successfully obtained old_selector */
-	if (ret == 0 && _regulator_is_enabled(rdev) && old_selector >= 0 &&
+	if (ret == 0 && !rdev->constraints->ramp_disable &&
+	    _regulator_is_enabled(rdev) && old_selector >= 0 &&
 	    old_selector != selector && rdev->desc->ops->set_voltage_time_sel) {
 
 		delay = rdev->desc->ops->set_voltage_time_sel(rdev,

drivers/regulator/of_regulator.c

@@ -21,6 +21,7 @@ static void of_get_regulation_constraints(struct device_node *np,
 {
 	const __be32 *min_uV, *max_uV, *uV_offset;
 	const __be32 *min_uA, *max_uA, *ramp_delay;
+	struct property *prop;
 	struct regulation_constraints *constraints = &(*init_data)->constraints;
 
 	constraints->name = of_get_property(np, "regulator-name", NULL);
@@ -64,9 +65,14 @@ static void of_get_regulation_constraints(struct device_node *np,
 	if (of_property_read_bool(np, "regulator-allow-bypass"))
 		constraints->valid_ops_mask |= REGULATOR_CHANGE_BYPASS;
 
-	ramp_delay = of_get_property(np, "regulator-ramp-delay", NULL);
-	if (ramp_delay)
-		constraints->ramp_delay = be32_to_cpu(*ramp_delay);
+	prop = of_find_property(np, "regulator-ramp-delay", NULL);
+	if (prop && prop->value) {
+		ramp_delay = prop->value;
+		if (*ramp_delay)
+			constraints->ramp_delay = be32_to_cpu(*ramp_delay);
+		else
+			constraints->ramp_disable = true;
+	}
 }
 
 /**

include/linux/regulator/machine.h

@@ -134,6 +134,7 @@ struct regulation_constraints {
 	unsigned always_on:1;	/* regulator never off when system is on */
 	unsigned boot_on:1;	/* bootloader/firmware enabled regulator */
 	unsigned apply_uV:1;	/* apply uV constraint if min == max */
+	unsigned ramp_disable:1; /* disable ramp delay */
 };
 
 /**