Hi, I am doing some overlay for fbtft LCD driver - SSD1322. I did compile an add my patch, now I would like to load the LCD driver with DT overlay. This is what I have done:

/dts-v1/;
/plugin/;

/ {
    compatible = "rockchip,rk3399";

    fragment@0 {
        target = <&spi1>;
        __overlay__ {
            status = "okay";
            
        };
    };

    fragment@1 {
        target = <&spi1>;
        __overlay__ {
            /* needed to avoid dtc warning */
            #address-cells = <1>;
            #size-cells = <0>;
            status = "okay";

            mytft@0{
                compatible = "solomon,ssd1322";
                reg = <0>;
                spi-max-frequency = <1000000>;
                buswidth = <8>;
                rotate = <0>;
                bgr = <0>;
                fps = <20>;
                reset-gpios = <0>, <1 21 1 0xae>;
                dc-gpios = <0>, <1 21 1 0xae>;
                debug = <0>;
                status = "okay";
            };
        };
    };
};

Now the problem is, that I haven't found any information on how those GPIOs are defined. I took pieces of code here and there, the gpio declaration comes from user @martinayotte

 

            cs-gpio = <0>, <1 21 1 0xae>;
//            csgpio = <&gpio1 21 1 0xae>;
//            csgpio = <&pinctrl/gpio1@ff730000 21 1 0xae>;

He uses several ways to declare them, but what really means <0>, <1 21 1 0xae> ? How can I compute this kind of coding for arbitrary RK3399 Gpio?

0001-Signed-off-by-root-marko.bursic73-gmail.com.patch

 

EDIT:

 

I have found this

https://forum.radxa.com/t/how-to-control-the-gpio/148/32

 

So my assumption is to control GPIO4_D5 it should be   dc-gpios = <&gpio4 29 1 0xae>;  Since D=3, then 3*8+5=29. Still don't know what 1 and 0xae means, but obviously is wrong. The dmesg reveals invalid GPIO .

 

Call trace:
[   81.742210]  gpio_to_desc+0xa8/0xf0
[   81.742222]  write_vmem+0x38/0x190
[   81.742232]  fbtft_update_display+0xd0/0x218
[   81.742241]  fbtft_deferred_io+0xc0/0xd8
[   81.742250]  fb_deferred_io_work+0xdc/0x158
[   81.742261]  process_one_work+0x1e0/0x338
[   81.742270]  worker_thread+0x40/0x440
[   81.742282]  kthread+0x120/0x128
[   81.742294]  ret_from_fork+0x10/0x18
[   81.742301] ---[ end trace 8a7abacfafe1f15a ]---
[   81.945879] ------------[ cut here ]------------
[   81.945890] invalid GPIO -257459296
[   81.945950] WARNING: CPU: 4 PID: 507 at drivers/gpio/gpiolib.c:126 gpio_to_desc+0xa8/0xf0
 

Hello Marko Buršič

 

there are some explaination on the page u linked:

GPIO 4         D       5 = 157  

         4*32 + 3*8 + 5 = 157  

 

i don´t know what "0xae"  stands for but it could be something like pull up/down /activ low/high 

so wenn you see something like 

csgpio = <&gpio1 21 1 0xae> on rk3399 it would call  

translated to GPIO Number

          1*32 + 2*8 + 5 = 53

             32 +   16 + 5 = 53

             32  +   21      = 53

GPIO   1         C       5 = 53

 

but on the 40 Pin Header i can't find a pin number corrospondending to GPIO number 53.

so maybe you would like to call ?!

Pin#	GPIO	Function1	GPIO number
24	GP1B2	SPI1_CSn	42

 

you would write something like ( whatever 0xae mean)

 

csgpio = <&gpio1 10 1 0xae>;

 

          1*32 + 1*8 + 2 = 42

             32 +   8 + 2 = 42

             32  +   10     = 42

GPIO   1         B      2 = 42

 

but i´m just guessing