Re: [PATCH] gpio: samsung: add devicetree init for s3c24xx arches

Am Montag, 27. August 2012, 11:51:27 schrieb Vasily Khoruzhick:

On Mon, Aug 27, 2012 at 12:44 PM, Heiko Stübner [off-list ref] wrote:

quoted

Hi Vasily,

I'm not sure I follow :-) .

The compatible property here only sets the mechanism on how to handle the
gpios defined in the devicetree - here to use the s3c24xx-style. As you
can see in gpio-samsung.c the handling is already unified for all the
s3c24xx architectures.

The definition of what gpio banks exist is then done in the respective
devicetree file for the individual SoC. And of course here one would have
individual definitions, depending on the banks present.

For reference my quite empty s3c2416.dtsi file currently looks like:

/include/ "skeleton.dtsi"

/ {

        compatible = "samsung,s3c2416";
        
        cpus {
        
                cpu@0 {
                
                        compatible = "arm,arm926ejs";
                
                };
        
        };
        
        gpio-controllers {
        
                #address-cells = <1>;
                #size-cells = <1>;
                gpio-controller;
                ranges;
                
                gpa: gpio-controller@56000000 {
                
                        compatible = "samsung,s3c24xx-gpio";
                        reg = <0x56000000 0x10>;
                        #gpio-cells = <3>;
                
                };
                
                gpb: gpio-controller@56000010 {
                
                        compatible = "samsung,s3c24xx-gpio";
                        reg = <0x56000010 0x10>;
                        #gpio-cells = <3>;
                
                };

[ ... ]

quoted

        };

};

Other s3c24xx SoCs would of course need to define their own.

I see. But how does it handle GPA bank (which is output-only, and
GPACON differs a bit from GP{B-J}CON? And some banks has lower number
(not 16) of GPIOs, like GPH.

Also, what would be value for S3C_GPIO_END?

The creation of the banks is still done in gpio-samsung.c and the special 
handling of bank-a is still sitting in the s3c24xx_gpios[] array there.

In general the gpios are still created completely like before and the 
devicetree information is only attached to them so that dt-devices can 
reference them.

As you can see in the original patch, after the respective chip got created in 
s3c24xx_gpiolib_add_chips, s3c24xx_gpiolib_attach_ofnode searches for the 
representation of it in the device tree and attaches this to the chip.

So nothing really changed, except that dt-devices can now reference gpios and 
if they do s3c24xx_gpio_xlate will get called to configure them with the 
target values from the dt.

Currently I'm also only using it in a mixed mode configuration [1], 
supplementing a normal machine file with some devices from the devicetree - 
especially as I still need to figure out, what to do about the interrupt 
controller.


Heiko


[1] https://github.com/mmind/linux-es600/blob/topic/es600-
devel/arch/arm/boot/dts/s3c24xx-sg06.dts