[PATCH 2/3] arm: kirkwood: factor pinmux descriptors for OpenBlocks A6

[thomas.petazzoni@free-electrons.com (Thomas Petazzoni)]

Dear Andrew Lunn,

On Wed, 6 Mar 2013 19:16:48 +0100, Andrew Lunn wrote:
> On Wed, Mar 06, 2013 at 05:23:40PM +0100, Thomas Petazzoni wrote:
> > The OpenBlocks A6 .dts file was using a long list of pinmux
> > descriptors to select each GPIO of the external GPIO connector and the
> > internal DIP switch, for no apparent reason. This commit factors those
> > GPIO pins into two descriptors: one for the external GPIO connector
> > and one for the internal DIP switch.
> 
> Hi Thomas
> 
> There is no need to pinmux gpio pins at all. The pinctrl driver does
> it when the gpio driver requests the pins.
> 
> This stems from an error i made. I also didn't know this and added
> hogs for gpio pins as i converted some boards. Others have then just
> cut/paste my error.....

I was looking at this today to send an updated version of those
patches. However, it turns out that having the pinctrl-0 property to
associate pinmux configurations to a device has an advantage: pinctrl
knows about this association.

If you keep the pinctrl-0 property in gpio-leds and gpio-keys,
then /sys/kernel/debug/pinctrl/f1010000.pinctrl/pinmux-pins looks like
this:

======================================================================
pin 38 (PIN38): gpio_keys.2 mvebu-gpio:38 function gpio group mpp38
pin 39 (PIN39): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 40 (PIN40): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 41 (PIN41): gpio-leds.1 mvebu-gpio:41 function gpio group mpp41
pin 42 (PIN42): gpio-leds.1 mvebu-gpio:42 function gpio group mpp42
pin 43 (PIN43): gpio-leds.1 mvebu-gpio:43 function gpio group mpp43
======================================================================

On the other hand, if you remove the pinctrl-0 property, the same file
looks like this:

======================================================================
pin 38 (PIN38): (MUX UNCLAIMED) mvebu-gpio:38
pin 39 (PIN39): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 40 (PIN40): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 41 (PIN41): (MUX UNCLAIMED) mvebu-gpio:41
pin 42 (PIN42): (MUX UNCLAIMED) mvebu-gpio:42
pin 43 (PIN43): (MUX UNCLAIMED) mvebu-gpio:43
======================================================================

So you no longer know by what device the pin is claimed. It is not
horrible of course, but I find it quite nice to be able to see which
pin is used by what device.

What do you think?

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com