[PATCH V2 1/2] regulator: pwm: DT: Add ramp delay for exponential voltage transition

[PATCH V2 1/2] regulator: pwm: DT: Add ramp delay for exponential voltage transition

[Laxman Dewangan]

Some PWM regulator has the exponential transition in voltage change as
opposite to fixed slew-rate linear transition on other regulators.
For such PWM regulators, add the property to tell that voltage change
is exponential and having fixed delay for any level of change.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
CC: Douglas Anderson <dianders@chromium.org>
CC: Aleksandr Frid <afrid@nvidia.com>

---
This patch is continuation of discussion on patch
	regulator: pwm: Fix regulator ramp delay for continuous mode
https://patchwork.kernel.org/patch/9216857/
where is it discussed to have separate property for PWM which has
exponential voltage transition.

Changes from V1:
- Pass the flag to tell that voltage ramp is exponential instead of
  providing delay.
---
 .../devicetree/bindings/regulator/pwm-regulator.txt          | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
index 3aeba9f..2d9ef3a 100644
--- a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
+++ b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
@@ -54,6 +54,18 @@ Optional properties:
 --------------------
 - enable-gpios:		GPIO to use to enable/disable the regulator
 
+- voltage-ramp-exponential: Boolean, Some of PWM regulator has the exponential
+			transition in voltage ramp as opposite to fixed
+			slew-rate linear transition on other regulators.
+			For such PWM regulator, presence of this property will
+			tell that value of the regulator ramp delay provided by
+			DT property "regulator-ramp-delay" is exponential and
+			fixed delay for any voltage level change.
+			If PWM regulator supports the fixed linear slew rate
+			then this property should be absent from DT node and
+			property "regulator-ramp-delay" is used as linear slew
+			rate.
+
 Any property defined as part of the core regulator binding can also be used.
 (See: ../regulator/regulator.txt)
 
-- 
2.1.4

[PATCH V2 2/2] regulator: pwm: Add ramp delay for exponential voltage transition

[Laxman Dewangan]

Some PWM regulator has the exponential transition in voltage change
as opposite to fixed slew-rate linear transition on other regulators.
For such PWM regulators, add support for handling the exponential
voltage ramp delay.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
CC: Douglas Anderson <dianders@chromium.org>
CC: Aleksandr Frid <afrid@nvidia.com>

---
This patch is continuation of discussion on patch
	regulator: pwm: Fix regulator ramp delay for continuous mode
https://patchwork.kernel.org/patch/9216857/
where is it discussed to have separate property for PWM which has
exponential voltage transition.

Changes from V1:
- Use new DT property to finding that voltage ramp is exponential or
  not and use flag for having fixed delay for all voltage change.
---
 drivers/regulator/pwm-regulator.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/regulator/pwm-regulator.c b/drivers/regulator/pwm-regulator.c
index 1b88e0e1..bcffeee 100644
--- a/drivers/regulator/pwm-regulator.c
+++ b/drivers/regulator/pwm-regulator.c
@@ -233,6 +233,24 @@ static int pwm_regulator_set_voltage(struct regulator_dev *rdev,
 	return 0;
 }
 
+/**
+ * Some of PWM regulators have exponential voltage ramp. On such PWM
+ * regulators, voltage settling time is same regardless of voltage
+ * level change.
+ */
+static int pwm_regulator_set_voltage_time(struct regulator_dev *rdev,
+					  int old_uV, int new_uV)
+{
+	return rdev->constraints->ramp_delay;
+}
+
+static int pwm_regulator_set_voltage_time_sel(struct regulator_dev *rdev,
+					      unsigned int old_selector,
+					      unsigned int new_selector)
+{
+	return rdev->constraints->ramp_delay;
+}
+
 static struct regulator_ops pwm_regulator_voltage_table_ops = {
 	.set_voltage_sel = pwm_regulator_set_voltage_sel,
 	.get_voltage_sel = pwm_regulator_get_voltage_sel,
@@ -294,17 +312,25 @@ static int pwm_regulator_init_table(struct platform_device *pdev,
 	drvdata->desc.ops = &drvdata->ops;
 	drvdata->desc.n_voltages	= length / sizeof(*duty_cycle_table);
 
+	if (of_property_read_bool(np, "voltage-ramp-exponential"))
+		drvdata->ops.set_voltage_time_sel =
+					pwm_regulator_set_voltage_time_sel;
 	return 0;
 }
 
 static int pwm_regulator_init_continuous(struct platform_device *pdev,
 					 struct pwm_regulator_data *drvdata)
 {
+	struct device_node *np = pdev->dev.of_node;
 	u32 dutycycle_range[2] = { 0, 100 };
 	u32 dutycycle_unit = 100;
 
 	memcpy(&drvdata->ops, &pwm_regulator_voltage_continuous_ops,
 	       sizeof(drvdata->ops));
+
+	if (of_property_read_bool(np, "voltage-ramp-exponential"))
+		drvdata->ops.set_voltage_time = pwm_regulator_set_voltage_time;
+
 	drvdata->desc.ops = &drvdata->ops;
 	drvdata->desc.continuous_voltage_range = true;
 
-- 
2.1.4

Re: [PATCH V2 1/2] regulator: pwm: DT: Add ramp delay for exponential voltage transition

[Rob Herring]

On Fri, Nov 18, 2016 at 08:05:55PM +0530, Laxman Dewangan wrote:
> Some PWM regulator has the exponential transition in voltage change as
> opposite to fixed slew-rate linear transition on other regulators.
> For such PWM regulators, add the property to tell that voltage change
> is exponential and having fixed delay for any level of change.
> 
> Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
> CC: Douglas Anderson <dianders@chromium.org>
> CC: Aleksandr Frid <afrid@nvidia.com>
> 
> ---
> This patch is continuation of discussion on patch
> 	regulator: pwm: Fix regulator ramp delay for continuous mode
> https://patchwork.kernel.org/patch/9216857/
> where is it discussed to have separate property for PWM which has
> exponential voltage transition.
> 
> Changes from V1:
> - Pass the flag to tell that voltage ramp is exponential instead of
>   providing delay.
> ---
>  .../devicetree/bindings/regulator/pwm-regulator.txt          | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
> index 3aeba9f..2d9ef3a 100644
> --- a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
> +++ b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
> @@ -54,6 +54,18 @@ Optional properties:
>  --------------------
>  - enable-gpios:		GPIO to use to enable/disable the regulator
>  
> +- voltage-ramp-exponential: Boolean, Some of PWM regulator has the exponential
> +			transition in voltage ramp as opposite to fixed
> +			slew-rate linear transition on other regulators.
> +			For such PWM regulator, presence of this property will
> +			tell that value of the regulator ramp delay provided by
> +			DT property "regulator-ramp-delay" is exponential and
> +			fixed delay for any voltage level change.
> +			If PWM regulator supports the fixed linear slew rate
> +			then this property should be absent from DT node and
> +			property "regulator-ramp-delay" is used as linear slew
> +			rate.

Sorry, but on further thought, I don't think we should mix different 
units for the same property. Also, the fact that the ramp is exponential 
is irrelevant. You just want an absolute delay time rather than a rate, 
right? So instead, how about just "regulator-ramp-time-us". Roughly what 
you had in v1, but not PWM specific.

Rob

Re: [PATCH V2 1/2] regulator: pwm: DT: Add ramp delay for exponential voltage transition

[Laxman Dewangan]

On Monday 21 November 2016 09:47 PM, Rob Herring wrote:
> On Fri, Nov 18, 2016 at 08:05:55PM +0530, Laxman Dewangan wrote:
>> Some PWM regulator has the exponential transition in voltage change as
>> opposite to fixed slew-rate linear transition on other regulators.
>> For such PWM regulators, add the property to tell that voltage change
>> is exponential and having fixed delay for any level of change.
>>
>> Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
>> CC: Douglas Anderson <dianders@chromium.org>
>> CC: Aleksandr Frid <afrid@nvidia.com>
>>
>> ---
>> This patch is continuation of discussion on patch
>> 	regulator: pwm: Fix regulator ramp delay for continuous mode
>> https://patchwork.kernel.org/patch/9216857/
>> where is it discussed to have separate property for PWM which has
>> exponential voltage transition.
>>
>> Changes from V1:
>> - Pass the flag to tell that voltage ramp is exponential instead of
>>    providing delay.
>> ---
>>   .../devicetree/bindings/regulator/pwm-regulator.txt          | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
>> index 3aeba9f..2d9ef3a 100644
>> --- a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
>> +++ b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
>> @@ -54,6 +54,18 @@ Optional properties:
>>   --------------------
>>   - enable-gpios:		GPIO to use to enable/disable the regulator
>>   
>> +- voltage-ramp-exponential: Boolean, Some of PWM regulator has the exponential
>> +			transition in voltage ramp as opposite to fixed
>> +			slew-rate linear transition on other regulators.
>> +			For such PWM regulator, presence of this property will
>> +			tell that value of the regulator ramp delay provided by
>> +			DT property "regulator-ramp-delay" is exponential and
>> +			fixed delay for any voltage level change.
>> +			If PWM regulator supports the fixed linear slew rate
>> +			then this property should be absent from DT node and
>> +			property "regulator-ramp-delay" is used as linear slew
>> +			rate.
> Sorry, but on further thought, I don't think we should mix different
> units for the same property. Also, the fact that the ramp is exponential
> is irrelevant. You just want an absolute delay time rather than a rate,
> right? So instead, how about just "regulator-ramp-time-us". Roughly what
> you had in v1, but not PWM specific.

Can we say "regulator-settling-time-us" and make it generic i.e. part of 
the regulator core instead of PWM regulator specific?

So no change for "regulator-ramp-delay".
new property "regulator-settling-time-us" for fixed settling time in any 
voltage level change.

Re: [PATCH V2 1/2] regulator: pwm: DT: Add ramp delay for exponential voltage transition

[Rob Herring]

On Tue, Nov 22, 2016 at 2:50 AM, Laxman Dewangan <ldewangan@nvidia.com> wrote:
>
> On Monday 21 November 2016 09:47 PM, Rob Herring wrote:
>>
>> On Fri, Nov 18, 2016 at 08:05:55PM +0530, Laxman Dewangan wrote:
>>>
>>> Some PWM regulator has the exponential transition in voltage change as
>>> opposite to fixed slew-rate linear transition on other regulators.
>>> For such PWM regulators, add the property to tell that voltage change
>>> is exponential and having fixed delay for any level of change.
>>>
>>> Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
>>> CC: Douglas Anderson <dianders@chromium.org>
>>> CC: Aleksandr Frid <afrid@nvidia.com>
>>>
>>> ---
>>> This patch is continuation of discussion on patch
>>>         regulator: pwm: Fix regulator ramp delay for continuous mode
>>> https://patchwork.kernel.org/patch/9216857/
>>> where is it discussed to have separate property for PWM which has
>>> exponential voltage transition.
>>>
>>> Changes from V1:
>>> - Pass the flag to tell that voltage ramp is exponential instead of
>>>    providing delay.
>>> ---
>>>   .../devicetree/bindings/regulator/pwm-regulator.txt          | 12
>>> ++++++++++++
>>>   1 file changed, 12 insertions(+)
>>>
>>> diff --git
>>> a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
>>> b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
>>> index 3aeba9f..2d9ef3a 100644
>>> --- a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
>>> +++ b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
>>> @@ -54,6 +54,18 @@ Optional properties:
>>>   --------------------
>>>   - enable-gpios:               GPIO to use to enable/disable the
>>> regulator
>>>   +- voltage-ramp-exponential: Boolean, Some of PWM regulator has the
>>> exponential
>>> +                       transition in voltage ramp as opposite to fixed
>>> +                       slew-rate linear transition on other regulators.
>>> +                       For such PWM regulator, presence of this property
>>> will
>>> +                       tell that value of the regulator ramp delay
>>> provided by
>>> +                       DT property "regulator-ramp-delay" is exponential
>>> and
>>> +                       fixed delay for any voltage level change.
>>> +                       If PWM regulator supports the fixed linear slew
>>> rate
>>> +                       then this property should be absent from DT node
>>> and
>>> +                       property "regulator-ramp-delay" is used as linear
>>> slew
>>> +                       rate.
>>
>> Sorry, but on further thought, I don't think we should mix different
>> units for the same property. Also, the fact that the ramp is exponential
>> is irrelevant. You just want an absolute delay time rather than a rate,
>> right? So instead, how about just "regulator-ramp-time-us". Roughly what
>> you had in v1, but not PWM specific.
>
>
> Can we say "regulator-settling-time-us" and make it generic i.e. part of the
> regulator core instead of PWM regulator specific?

Sure.

Rob