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

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Date:   Tue, 15 Nov 2016 08:27:53 -0600
From:   Rob Herring <robh@...nel.org>
To:     Laxman Dewangan <ldewangan@...dia.com>
Cc:     Mark Brown <broonie@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Aleksandr Frid <afrid@...dia.com>
Subject: Re: [PATCH 1/2] regulator: pwm: DT: Add ramp delay for exponential
 voltage transition

On Tue, Nov 15, 2016 at 5:42 AM, Laxman Dewangan <ldewangan@...dia.com> wrote:
>
> On Monday 14 November 2016 09:18 PM, Rob Herring wrote:
>>
>> On Fri, Nov 04, 2016 at 11:07:54PM +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 for providing the delay
>>> from DT node.
>>>
>>> Add DT binding details of the new property
>>> "pwm-regulator-voltage-ramp-time-us" added for providing voltage
>>> transition delay.
>>>
>>> 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.
>>> ---
>>>   Documentation/devicetree/bindings/regulator/pwm-regulator.txt | 10
>>> ++++++++++
>>>   1 file changed, 10 insertions(+)
>>>
>>> diff --git
>>> a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
>>> b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
>>> index 3aeba9f..a163f42 100644
>>> --- a/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
>>> +++ b/Documentation/devicetree/bindings/regulator/pwm-regulator.txt
>>> @@ -54,6 +54,16 @@ Optional properties:
>>>   --------------------
>>>   - enable-gpios:               GPIO to use to enable/disable the
>>> regulator
>>>   +- pwm-regulator-voltage-ramp-time-us: Integer, voltage ramp time in
>>
>> This is a really long name. Drop the 'pwm-regulator-' part as it is
>> redundant. The fact that it is PWM reg specific is captured as it is
>> documented that way.
>>
>
> We already have the regulator-ramp-delay from the regulator core.
> Just wanted to make this (pwm-regulator-voltage-ramp-time-us) for pwm
> specific.

Neither of these are very clear that one is linear and one is
exponential. Maybe you should use the existing property to express the
time and just add a boolean property like "voltage-ramp-exponential"?

> Can we have "pwm-regulator-ramp-delay" or "pwm-regulator-settling-time-us"?

How are those better? Same comment applies.

Rob