linux-kernel - Re: [PATCH 6/7] pinctrl: tegra: Add DT binding for io pads control

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Message-ID: <57111778.5030500@nvidia.com>
Date:	Fri, 15 Apr 2016 22:01:52 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	<thierry.reding@...il.com>, <linus.walleij@...aro.org>,
	<gnurou@...il.com>, <robh+dt@...nel.org>, <mark.rutland@....com>,
	<jonathanh@...dia.com>, <linux-tegra@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-gpio@...r.kernel.org>
Subject: Re: [PATCH 6/7] pinctrl: tegra: Add DT binding for io pads control


On Friday 15 April 2016 10:05 PM, Stephen Warren wrote:
> On 04/12/2016 08:56 AM, Laxman Dewangan wrote:
>> NVIDIA Tegra210 supports the IO pads which can operate at 1.8V
>> or 3.3V I/O voltage levels. Also IO pads can be configured for
>> power down state if it is not in used. SW needs to configure the
>> voltage level of IO pads based on IO rail voltage and its power
>> state based on platform usage.
>>
>> Add DT binding document for detailing the DT properties for
>> configuring IO pads voltage levels and its power state.
>
> I hope that we only intend to use this in the case where Linux must 
> make dynamic changes to the IO voltage (e.g. SD cards switching 
> between speeds).
>
> All static settings, and good boot defaults, should be set up by 
> system FW. Perhaps not all FW does this on Tegra210 platforms:-( I 
> hope that on future chips, the same FW that sets up the static pinmux 
> sets up the static IO voltage configuration, in exactly the same way.

Exactly yes.