linux-kernel - Re: [PATCH V4 2/2] pinctrl: tegra: Add driver to configure voltage and power of io pads

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Message-ID: <583879A8.7020401@nvidia.com>
Date:   Fri, 25 Nov 2016 23:19:28 +0530
From:   Laxman Dewangan <ldewangan@...dia.com>
To:     Jon Hunter <jonathanh@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>
CC:     <linus.walleij@...aro.org>, <robh+dt@...nel.org>,
        <mark.rutland@....com>, <swarren@...dotorg.org>,
        <gnurou@...il.com>, <joe@...ches.com>,
        <yamada.masahiro@...ionext.com>, <linux-gpio@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4 2/2] pinctrl: tegra: Add driver to configure voltage
 and power of io pads


On Friday 25 November 2016 10:59 PM, Jon Hunter wrote:
> On 25/11/16 12:04, Laxman Dewangan wrote:
>> Thanks Thierry for review.
>>
>> On Friday 25 November 2016 03:27 PM, Thierry Reding wrote:
>>> * PGP Signed by an unknown key
>>>
>>> On Thu, Nov 24, 2016 at 02:08:54PM +0530, Laxman Dewangan wrote:
>>>> +      NVIDIA Tegra124/210 SoC has IO pads which supports multi-voltage
>>>> +      level of interfacing and deep power down mode of IO pads. The
>>>> +      voltage of IO pads are SW configurable based on IO rail of that
>>>> +      pads on T210. This driver provides the interface to change IO pad
>>>> +      voltage and power state via pincontrol interface.
>>> This has a lot of chip-specific text. Will all of that have to be
>>> updated if support for new chips is added?
>> Then saying that Tegra124 and later..
>> Hoping, people know our chip releasing sequence as numbering are not in
>> sequence.
>>
>>>> +#include <linux/regulator/consumer.h>
>>>> +#include <soc/tegra/pmc.h>
>>> Have you considered moving this code into the PMC driver? It seems a
>>> little over the top to go through all of the platform device creation
>>> and driver registration dance only to call into a public API later on.
>> Yes, we had discussion on this and suggestion came to use the pinctrl
>> framework.
>> If we do in the pmc driver then we will need lots of DT processing for
>> getting information from DT which we can directly get from the pinctrl
>> core framework.
>> Also client driver may need to have the control dynamically and get the
>> IO pads from DT. So implementing all in pmc will be huge duplication
>> over already existing framework.
> I don't follow. We already did something similar for the Tegra DPAUX
> driver [0].
>
> Cheers
> Jon
>
> [0]
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/gpu/drm/tegra/dpaux.c?id=0751bb5c44fe1aa9494ce259d974c3d249b73a84

In the above dpaux driver,  you used the pinctrl framework and its core 
functionality for the device tree interfacing and client interfacing.

The same thing I am saying here, we should not avoid the pinctrl 
framework. The client driver will use the pinctrl framework for the IO 
pad configurations, not direct PMC APIs.