linux-kernel - Re: [PATCH 1/2] regulator: DT: Add support to scale ramp delay based on platform behavior

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Date:	Fri, 1 Apr 2016 01:18:23 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Mark Brown <broonie@...nel.org>
CC:	Bjorn Andersson <bjorn@...o.se>,
	Bjorn Andersson <bjorn.andersson@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Liam Girdwood <lgirdwood@...il.com>,
	Stephen Warren <swarren@...dotorg.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Gandhar Dighe <gdighe@...dia.com>,
	Stuart Yates <syates@...dia.com>
Subject: Re: [PATCH 1/2] regulator: DT: Add support to scale ramp delay based
 on platform behavior


On Friday 01 April 2016 12:52 AM, Mark Brown wrote:
> * PGP Signed by an unknown key
>
> On Fri, Apr 01, 2016 at 12:29:05AM +0530, Laxman Dewangan wrote:
>> On Friday 01 April 2016 12:29 AM, Mark Brown wrote:
>> But here is the stuff without typo ;-)
>> Device supports 5mV/us and 100mV/us which is not in observed value.
> So why doesn't the device end up configuring 100mV/us when asked for
> 50mv/us?  That's reasonably expected - the configured ramp rate is a
> maximum rate given that this is used to limit inrush current.
>
>

We did this to adjust device configuration to nearest higher side but 
this is not working well on some of cases.

On same device, DCDC (SD) rails support 4 ramp configurations, 
13.75mV/us, 27.5mV/us, 55mV/us and 100mV/us.

HW team measured the  ramp time at 7.5mV/us when device configured at 
27.5mV/uS.

So as per above, it will be adjusted to 13.75mV/us (nearest higher side) 
for device configuration but this device need to configure for 27.5mV/us.