linux-kernel - Re: [PATCH 7/7] pinctrl: tegra: Add driver to configure voltage and power state of io pads

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Message-ID: <5710D4E2.2030801@nvidia.com>
Date:	Fri, 15 Apr 2016 17:17:46 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Jon Hunter <jonathanh@...dia.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH 7/7] pinctrl: tegra: Add driver to configure voltage and
 power state of io pads


On Friday 15 April 2016 04:45 PM, Linus Walleij wrote:
> On Fri, Apr 15, 2016 at 11:55 AM, Laxman Dewangan <ldewangan@...dia.com> wrote:
>> On Friday 15 April 2016 02:55 PM, Linus Walleij wrote:
>>> If the pin could actually set a voltage level it would have a regulator.
>>> I don't believe that. I think it is selecting one of two rails which
>>> could theoretically hold two totally different voltages.
>>>
>>> And that is what power-source is about.
>> The IO rails connected to PMIC rail and connection does not get change.
>> We change the voltage of PMIC rails via regulator calls. And then configure
>> pads for the new voltage.
> Aha I get it! So you adjust something in the I/O-cell so that it is adapted
> for the new voltage.
>
> OK that seems to be something new. I suspect
> power-voltage-select = <n>; where N i in uV would solve this?
> (We should use uV since regulators use this.)

Thanks for new property. I will make the unit and type same as the 
regulator framework.



>
> But to be sure we would like to know what is actually happening,
> electronically speaking, when you set this up. Do you have any
> idea?
>


 From electronic point of view, the value of VIL, VIH, VOL, VOH 
(Input/output voltage level for low and high state) are different when 
talking for 0 t 1.8V and 0 to 3.3V.