GPIO polarity in bindings for Freescale MXS

GPIO polarity in bindings for Freescale MXS

[Hector Palacios]

Hello,

Maybe I'm missing something but the MXS processors (at least i.MX23 and i.MX28) cannot 
set the polarity of the GPIOs, so shouldn't the #gpio-cells be 1?

(From Documentation/devicetree/bindings/gpio/fsl-imx-gpio.txt):

- #gpio-cells : Should be two.  The first cell is the pin number and
   the second cell is used to specify the gpio polarity:
       0 = active high
       1 = active low

Regards,
-- 
Héctor Palacios

Re: GPIO polarity in bindings for Freescale MXS

[Hector Palacios]

On 03/14/2013 11:02 AM, Hector Palacios wrote:
> Hello,
>
> Maybe I'm missing something but the MXS processors (at least i.MX23 and i.MX28) cannot
> set the polarity of the GPIOs, so shouldn't the #gpio-cells be 1?
>
> (From Documentation/devicetree/bindings/gpio/fsl-imx-gpio.txt):

Sorry, I meant: from Documentation/devicetree/bindings/gpio/gpio-mxs.txt

>
> - #gpio-cells : Should be two.  The first cell is the pin number and
>    the second cell is used to specify the gpio polarity:
>        0 = active high
>        1 = active low
>
> Regards,

Re: GPIO polarity in bindings for Freescale MXS

[Shawn Guo]

On Thu, Mar 14, 2013 at 01:35:47PM +0100, Hector Palacios wrote:
> On 03/14/2013 11:02 AM, Hector Palacios wrote:
> >Hello,
> >
> >Maybe I'm missing something but the MXS processors (at least i.MX23 and i.MX28) cannot
> >set the polarity of the GPIOs, so shouldn't the #gpio-cells be 1?
> >
> >(From Documentation/devicetree/bindings/gpio/fsl-imx-gpio.txt):
> 
> Sorry, I meant: from Documentation/devicetree/bindings/gpio/gpio-mxs.txt
> 
> >
> >- #gpio-cells : Should be two.  The first cell is the pin number and
> >   the second cell is used to specify the gpio polarity:
> >       0 = active high
> >       1 = active low

The second cell is used by client devices to specify their gpio
connection polarity.  Check of_get_named_gpio_flags() in
drivers/mmc/host/mxs-mmc.c for example to see how it's used.

Shawn

Re: GPIO polarity in bindings for Freescale MXS

[Stephen Warren]

On 03/14/2013 04:02 AM, Hector Palacios wrote:
> Hello,
> 
> Maybe I'm missing something but the MXS processors (at least i.MX23 and
> i.MX28) cannot set the polarity of the GPIOs, so shouldn't the
> #gpio-cells be 1?
> 
> (From Documentation/devicetree/bindings/gpio/fsl-imx-gpio.txt):
> 
> - #gpio-cells : Should be two.  The first cell is the pin number and
>   the second cell is used to specify the gpio polarity:
>       0 = active high
>       1 = active low

This field describes how software should interpret the GPIO values.

So, if the GPIO is specified as active-high, then software will
gpio_set_value(the_value_it_wants), whereas if the GPIO is specified as
active-low, then software will gpio_set_value(!the_value_it_wants). Note
that "software" here refers to the driver that requests/uses the GPIO,
and the flags can be retrieve using of_get_gpio_flags().