linux-kernel - Re: [PATCH V2] regulator: core: add support for configuring turn-on time through constraints

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Date:	Wed, 11 Sep 2013 23:39:18 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	"broonie@...nel.org" <broonie@...nel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"rob@...dley.net" <rob@...dley.net>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lgirdwood@...il.com" <lgirdwood@...il.com>
Subject: Re: [PATCH V2] regulator: core: add support for configuring turn-on
 time through constraints

On Wednesday 11 September 2013 11:16 PM, Stephen Warren wrote:
> On 09/11/2013 11:46 AM, Laxman Dewangan wrote:
>> On Wednesday 11 September 2013 10:47 PM, Stephen Warren wrote:
>>> - regulator-enable-ramp-delay: The time taken, in uSec, for the supply
>>> rail to reach the target voltage, plus/minus whatever tolerance the
>>> board design requires, once the regulator output itself has ramped up.
>>> This value is in addition to whatever built-in ramp time is inherent in
>>> the regulator's own internal design or configuration. This property
>>> describes the additional ramp time required due to board design issues
>>> such as trace capacitance and load on the supply.
>>>
>>> That's text repeats "additional" a bit, but I think describes the
>>> situation correctly?
>> I wanted to provide the absolute delay rather than additional delay on
>> top of inherit delay from device.
> I suppose that either is fine from a DT perspective. But, the regulator
> drivers already know their internal delay, so presumably driver code
> will have to take the value from DT, and subtract out whatever delay the
> driver already embodies, in order to calculate the extra delay required?
> Or, if this property is set, does the driver-specified delay just get
> ignored?

Yes, if property is available then driver-specified delay get ignored. 
Delay will be used from dt provided value.

Thanks,
Laxman


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