Re: DT on s3c24xx

Re: DT on s3c24xx

[Uwe Kleine-König]

Hello,

[Cc += linusw, linux-gpio]

On Wed, Dec 17, 2014 at 10:04:24PM +0300, Vasily Khoruzhick wrote:
> I'd like to port several s3c24xx to DT, and I'm stuck with s3c24xx LCD
> controller and power drivers for H1940 and RX1950.
> 
> Please see [1]. I want to move this function into another LCD power
> driver, but I'm not sure what to do with s3c_gpio_cfgpin(). I need to
> change pin function in runtime, and as far as I understand it should
> be handled via pinctrl driver somehow. But how?
You can pass >1 pinctrl setups to a node:

	somedevice {
		pinctrl-names = "default", "foo", "bar";
		pinctrl-0 = <&pinctrl_somedevice_default>;
		pinctrl-1 = <&pinctrl_somedevice_foo>;
		pinctrl-2 = <&pinctrl_somedevice_bar>;
		cfg-gpios = <&gpio4 12 3>, <&gpio2 7 5>;
	};

Then I think you can fiddle with pinctrl_select_state(). For the gpios
you can then use the standard gpiod_{request,direction_{in,out}put}
combo.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

Re: DT on s3c24xx

[Vasily Khoruzhick]

On Thu, Dec 18, 2014 at 10:52 AM, Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
> Hello,

Hi Uwe,

> [Cc += linusw, linux-gpio]
>
> On Wed, Dec 17, 2014 at 10:04:24PM +0300, Vasily Khoruzhick wrote:
>> I'd like to port several s3c24xx to DT, and I'm stuck with s3c24xx LCD
>> controller and power drivers for H1940 and RX1950.
>>
>> Please see [1]. I want to move this function into another LCD power
>> driver, but I'm not sure what to do with s3c_gpio_cfgpin(). I need to
>> change pin function in runtime, and as far as I understand it should
>> be handled via pinctrl driver somehow. But how?
> You can pass >1 pinctrl setups to a node:
>
>         somedevice {
>                 pinctrl-names = "default", "foo", "bar";
>                 pinctrl-0 = <&pinctrl_somedevice_default>;
>                 pinctrl-1 = <&pinctrl_somedevice_foo>;
>                 pinctrl-2 = <&pinctrl_somedevice_bar>;
>                 cfg-gpios = <&gpio4 12 3>, <&gpio2 7 5>;
>         };
>
> Then I think you can fiddle with pinctrl_select_state(). For the gpios
> you can then use the standard gpiod_{request,direction_{in,out}put}
> combo.

Thanks for you response!

Can I change pin function after gpio was requested? In low-power state
(i.e. when display is disabled) it's gpio driving some level,
and in active state it's some LCD controller pin (don't remember which
one exactly)

Regards,
Vasily

>
> Best regards
> Uwe
>
> --
> Pengutronix e.K.                           | Uwe Kleine-König            |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |

Re: DT on s3c24xx

[Alexandre Courbot]

On Thu, Dec 18, 2014 at 5:34 PM, Vasily Khoruzhick <anarsoul@gmail.com> wrote:
> On Thu, Dec 18, 2014 at 10:52 AM, Uwe Kleine-König
> <u.kleine-koenig@pengutronix.de> wrote:
>> Hello,
>
> Hi Uwe,
>
>> [Cc += linusw, linux-gpio]
>>
>> On Wed, Dec 17, 2014 at 10:04:24PM +0300, Vasily Khoruzhick wrote:
>>> I'd like to port several s3c24xx to DT, and I'm stuck with s3c24xx LCD
>>> controller and power drivers for H1940 and RX1950.
>>>
>>> Please see [1]. I want to move this function into another LCD power
>>> driver, but I'm not sure what to do with s3c_gpio_cfgpin(). I need to
>>> change pin function in runtime, and as far as I understand it should
>>> be handled via pinctrl driver somehow. But how?
>> You can pass >1 pinctrl setups to a node:
>>
>>         somedevice {
>>                 pinctrl-names = "default", "foo", "bar";
>>                 pinctrl-0 = <&pinctrl_somedevice_default>;
>>                 pinctrl-1 = <&pinctrl_somedevice_foo>;
>>                 pinctrl-2 = <&pinctrl_somedevice_bar>;
>>                 cfg-gpios = <&gpio4 12 3>, <&gpio2 7 5>;
>>         };
>>
>> Then I think you can fiddle with pinctrl_select_state(). For the gpios
>> you can then use the standard gpiod_{request,direction_{in,out}put}
>> combo.
>
> Thanks for you response!
>
> Can I change pin function after gpio was requested? In low-power state
> (i.e. when display is disabled) it's gpio driving some level,
> and in active state it's some LCD controller pin (don't remember which
> one exactly)

If your driver can release the GPIO and change the pinctrl when
switching to active state (and change the pinctrl again and request
the GPIO when switching to low-power state) then this should be
doable. I suspect the switch is made by the same driver anyway, isn't
it?
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Re: DT on s3c24xx

[Linus Walleij]

On Thu, Dec 18, 2014 at 9:34 AM, Vasily Khoruzhick <anarsoul@gmail.com> wrote:

> Can I change pin function after gpio was requested? In low-power state
> (i.e. when display is disabled) it's gpio driving some level,
> and in active state it's some LCD controller pin (don't remember which
> one exactly)

Please read the section named "GPIO mode pitfalls" in
Documentation/pinctrl.txt very closely.

Two ways:

- You can use the GPIO and pin control interface to the same
  hardware in parallel. There is no blocking this since there
  is hardware out that that actually allow this. NOT
  RECOMMENDED.

- If the "GPIO mode" mentioned is only about e.g. grounding
  the pins in a low power state and then not really about using
  them as GPIO, extend the pin controller to be able to e.g.
  ground the pins with PIN_CONFIG_OUTPUT or
  PIN_CONFIG_LOW_POWER_MODE if you use
  generic bindings.

If the usecase is low power, the latter approach is recommended.

Yours,
Linus Walleij