[PATCH V3] regulator: core: add support for configuring turn-on time through constraints

[PATCH V3] regulator: core: add support for configuring turn-on time through constraints

[Laxman Dewangan]

The Turn-on time of the regulator depends on the regulator device's
electrical characteristics. Sometimes regulator turn-on time also
depends on the capacitive load on the given platform and it can be
more than the datasheet value.

The driver provides the enable-time as per datasheet.

Add support for configure the enable ramp time through regulator
constraints so that regulator core can take this value for enable
time for that regulator.

Signed-off-by: Laxman Dewangan <ldewangan-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
---
Changes from V1:
- Change property name to regulator-enable-ramp-delay and add more details
  in DT doc.
- add the valid pointer check for constraints before accessing it.

Changes from V2:
- Rephrase the descripton of property regulator-enable-ramp-delay.

 .../devicetree/bindings/regulator/regulator.txt    |    4 ++++
 drivers/regulator/core.c                           |    2 ++
 drivers/regulator/of_regulator.c                   |    6 ++++++
 include/linux/regulator/machine.h                  |    2 ++
 4 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/Documentation/devicetree/bindings/regulator/regulator.txt b/Documentation/devicetree/bindings/regulator/regulator.txt
index 2bd8f09..ca81945 100644
--- a/Documentation/devicetree/bindings/regulator/regulator.txt
+++ b/Documentation/devicetree/bindings/regulator/regulator.txt
@@ -14,6 +14,10 @@ Optional properties:
 - 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.
+- regulator-enable-ramp-delay: Turn-on time for regulator(in microsecond).
+  This is the time time taken to reach the target voltage from off state.
+  The delay specified in the DT to just completely override what the drivers
+  know.
 
 Deprecated properties:
 - regulator-compatible: If a regulator chip contains multiple
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index a01b8b3..5217c19 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1186,6 +1186,8 @@ overflow_err:
 
 static int _regulator_get_enable_time(struct regulator_dev *rdev)
 {
+	if (rdev->constraints && rdev->constraints->enable_time)
+		return rdev->constraints->enable_time;
 	if (!rdev->desc->ops->enable_time)
 		return rdev->desc->enable_time;
 	return rdev->desc->ops->enable_time(rdev);
diff --git a/drivers/regulator/of_regulator.c b/drivers/regulator/of_regulator.c
index 7827384..ea4f36f 100644
--- a/drivers/regulator/of_regulator.c
+++ b/drivers/regulator/of_regulator.c
@@ -23,6 +23,8 @@ static void of_get_regulation_constraints(struct device_node *np,
 	const __be32 *min_uA, *max_uA, *ramp_delay;
 	struct property *prop;
 	struct regulation_constraints *constraints = &(*init_data)->constraints;
+	int ret;
+	u32 pval;
 
 	constraints->name = of_get_property(np, "regulator-name", NULL);
 
@@ -73,6 +75,10 @@ static void of_get_regulation_constraints(struct device_node *np,
 		else
 			constraints->ramp_disable = true;
 	}
+
+	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 999b20c..670d154 100644
--- a/include/linux/regulator/machine.h
+++ b/include/linux/regulator/machine.h
@@ -95,6 +95,7 @@ struct regulator_state {
  * @initial_state: Suspend state to set by default.
  * @initial_mode: Mode to set at startup.
  * @ramp_delay: Time to settle down after voltage change (unit: uV/us)
+ * @enable_time: Turn-on time of the rails (unit: uS)
  */
 struct regulation_constraints {
 
@@ -129,6 +130,7 @@ struct regulation_constraints {
 	unsigned int initial_mode;
 
 	unsigned int ramp_delay;
+	unsigned int enable_time;
 
 	/* constraint flags */
 	unsigned always_on:1;	/* regulator never off when system is on */
-- 
1.7.1.1

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Re: [PATCH V3] regulator: core: add support for configuring turn-on time through constraints

[Stephen Warren]

On 09/17/2013 05:45 AM, Laxman Dewangan wrote:
> The Turn-on time of the regulator depends on the regulator device's
> electrical characteristics. Sometimes regulator turn-on time also
> depends on the capacitive load on the given platform and it can be
> more than the datasheet value.
> 
> The driver provides the enable-time as per datasheet.
> 
> Add support for configure the enable ramp time through regulator
> constraints so that regulator core can take this value for enable
> time for that regulator.

> diff --git a/Documentation/devicetree/bindings/regulator/regulator.txt b/Documentation/devicetree/bindings/regulator/regulator.txt

> +- regulator-enable-ramp-delay: Turn-on time for regulator(in microsecond).

You need a space before (. You don't even need the brackets.
microseconds not microsecond.

> +  This is the time time taken to reach the target voltage from off state.
> +  The delay specified in the DT to just completely override what the drivers
> +  know.

This description references driver behaviour which it really shouldn't.
Instead, it should describe the HW itself. How about the following text,
which I suggested last time:

- regulator-enable-ramp-delay: The time taken, in microseconds, for the
supply rail to reach the target voltage, plus/minus whatever tolerance
the board design requires. This property describes the total system ramp
time required due to the combination of internal ramping of the
regulator itself, and board design issues such as trace capacitance and
load on the supply.

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