linux-kernel - Re: [rtc-linux] [PATCH V2 3/5] gpio: add support for AMS AS3722 gpio driver

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Message-ID: <5240117C.8060300@nvidia.com>
Date:	Mon, 23 Sep 2013 15:31:32 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	"rtc-linux@...glegroups.com" <rtc-linux@...glegroups.com>,
	Lee Jones <lee.jones@...aro.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Mark Brown <broonie@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Rob Landley <rob@...dley.net>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	Grant Likely <grant.likely@...aro.org>,
	Florian Lobmaier <florian.lobmaier@....com>
Subject: Re: [rtc-linux] [PATCH V2 3/5] gpio: add support for AMS AS3722 gpio
 driver

On Monday 23 September 2013 02:56 PM, Linus Walleij wrote:
> On Mon, Sep 23, 2013 at 10:55 AM, Laxman Dewangan <ldewangan@...dia.com> wrote:
>> On Monday 23 September 2013 01:36 PM, Linus Walleij wrote:
>>> This is pin control. Do not try to shoehorn pin control drivers into
>>> the GPIO subsystem. Take a good day off, read through
>>> Documentation/pinctrl.txt and come back with a thoroughly rewritten
>>> driver in drivers/pinctrl/pinctrl-as3722.c.
> (...)
>> Yes, the appropriate location is pin control for pull up/down etc
>> configuration but with this device, the actual issue is with the way it is
>> require to configure the pull up/down and input/output of the pin. There is
>> no separate bits for pull up/down and direction and it is  clubbed together.
>> The register's bits are defined as:
>>
>> Selects the GPIO mode (I, I/O, Tri, Pulls) (BIT 2:0)
>>    0 : Input
>>    1 : Output (push and pull) VSUP_GPIO
>>    2 : Output/Input (open drain, only NMOS is active)
>>    3 : ADC input (Tristate)
>>    4 : Input with pull-up to VDD_GPIO_lv
>>    5 : Input with pull-down
>>    6 : Output/Input open drain (nmos) with pull-up to VDD_GPIO_lv,
>>    7 : Output (push and pull) VDD_GPIO_lv
>>
>> So I can not actually configure the pull up/down, open drain and direction
>> independently until every thing is known.
>> Direction come from gpio driver but pull up/down and open drain
>> configuration come from the pin control.
>> And this is only the reason to make all configuration in single driver.
> This is nothing special. Create a single combined GPIO and
> pin control driver using the pin control framework and device
> tree bindings.
>

Ok, I was thinking that we should not call gpiochip_add() from the pin 
control driver in any new driver and that's why I developed gpio driver 
but it seems it is allowed. I saw some of driver in pinctrl are doing 
pin control and gpio functionality in single driver i.e. 
pincntrl-nomadik, pinctrl-samsung, pincntrl-st etc.
So this gpio driver can be moved now to the pincntrl folder and can use 
pincontrol and gpio framework.

I will respin the change.


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