Subject: Re: [PATCH/RFC] powerpc: DBox2 Board Support

From: Jochen Friedrich <[email-masked]>
Date: Wed, 26 Dec 2007 16:12:30 +0100

Hi David,

>>>> +			// Port D is LCD exclusive. Don't export as GPIO
>>>> +			CPM1_PIO: pio@970 {
>>>> +				compatible = "fsl,cpm1-pario";
>>>> +				reg = <970 180>;
>>>> +				num-ports = <3>;
>>>> +				#gpio-cells = <2>;
>>>> +			};
>>>> +
>>>> +			lcd@970 {
>>>> +				reg = <970 10>;
>>>> +				compatible = "samsung,ks0713";
>>> Is this representing an LCD controller, or the display itself.  Either
>>> way I'm surprised there's something here in the SoC that has a
>>> compatible string that's not "fsl,something"
>> It's a LCD controller wired to PortD. PortD is used for four 1bit lines
>> and one 8bit bus.
> 
> I'm still kind of confused here.  Does the pio@970 node above
> represent the PortD controller?  If the LCD controller is accessed
> solely through PortD, then it should be a child of the PortD node.
> 
> At present, pio and lcd have overlapping reg resources which is
> certainly wrong.
> 

pio@970 represent 4 ports (A-D). Ports A-C are used as GPIO lines. Port D
is exclusively used for the LCD, but it needs an 8bit accessor. Unfortunately,
the GPIO API doesn't have such an accessor, so the LCD driver needs to access
Port D itself and needs to make sure no other driver can access Port D via the
GPIO API. The representation as child of pio seems reasonable.

Thanks,
Jochen