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

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Date:   Tue, 22 Nov 2016 14:20:20 +0530
From:   Laxman Dewangan <ldewangan@...dia.com>
To:     Rob Herring <robh@...nel.org>
CC:     <broonie@...nel.org>, <mark.rutland@....com>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        "Douglas Anderson" <dianders@...omium.org>,
        Aleksandr Frid <afrid@...dia.com>
Subject: Re: [PATCH V2 1/2] regulator: pwm: DT: Add ramp delay for exponential
 voltage transition


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@...dia.com>
>> CC: Douglas Anderson <dianders@...omium.org>
>> CC: Aleksandr Frid <afrid@...dia.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.