linux-kernel - Re: [PATCH 5/6] pinctrl: tegra: Add DT binding for io pads control

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Date:	Tue, 3 May 2016 14:33:25 +0100
From:	Jon Hunter <jonathanh@...dia.com>
To:	Laxman Dewangan <ldewangan@...dia.com>, <swarren@...dotorg.org>,
	<linus.walleij@...aro.org>, <gnurou@...il.com>,
	<robh+dt@...nel.org>, <mark.rutland@....com>,
	<thierry.reding@...il.com>
CC:	<linux-tegra@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH 5/6] pinctrl: tegra: Add DT binding for io pads control


On 03/05/16 13:54, Laxman Dewangan wrote:
> 
> On Tuesday 03 May 2016 06:14 PM, Jon Hunter wrote:
>> On 02/05/16 13:17, Laxman Dewangan wrote:
>>> +
>>> +The voltage supported on the pads are 1.8V and 3.3V. The enums are
>>> defined as:
>>> +    For 1.8V, use TEGRA_IO_PAD_POWER_SOURCE_1800000UV
>>> +    For 3.3V, use TEGRA_IO_PAD_POWER_SOURCE_3300000UV
>> Are these still necessary now that the driver is using uV? Can't we just
>> use integer values for 1800000 and 3300000 in the DTS directly?
>>
> The config param and value are packed in u32 with 16bit each So we can
> not make uV in 16bit until we do conversion of uV->mV.
> Hence suggestion came from Stephen that we can have enum for Nvidia
> specific and what actually it supports by HW. HW does not support any
> other voltage.

Ah yes I see.

> 
>>> +Required subnode-properties:
>>> +==========================
>>> +- pins : An array of strings. Each string contains the name of an IO
>>> pads. Valid
>>> +     values for these names are listed below.
>> Please see my previous comments.
> 
> This is taken from other dt binding docs for description. We can have
> array of string.

OK.

> As all value of pins are not supporting all property and hence I
> explicitly wrote under properties.

I don't find it very clear. I thought all pins support the low power
modes so I think it is clearer to list all the pin names under the pins
description.

>>> +Optional subnode-properties:
>>> +==========================
>>> +-nvidia,power-source-voltage:    Integer. The voltage level of IO
>>> pads. The
>> I think I prefer nvidia,io-voltage or something. You can describe what
>> this means in this doc. In fact, the current description here does not
>> explicitly state that this voltage, is the voltage the pad is configured
>> to operate at versus the voltage of the IO rail.
> 
> Linus suggested this dt property name to make more readable and generic
> and meaningful with other property :power-source.

OK.

Jon