Kernel FDT (3.14.28): Multiple display definitions

grim — Fri, 04 Nov 2016 18:32:50 GMT

We have a couple of different systems that we offer. Each has a different display.

One of the displays is split-mode, dual channel LVDS.

The other display is single-channel LVDS.

Both systems have the same kernel. Each has a different DTB (just because of the display).

I would like to have one kernel and one DTB that would run on either system but I'm having trouble wrapping my brain around how to accomplish this.

I use one device tree source file and I just comment out the display that I don't want for each DTB.

My display declaration looks like this.....

&ldb {
   status = "okay";
   /* AUO */
   split-mode = <1>;
   status = "okay";
   lvds-channel@0 {
       crtc = "ipu1-di1";
       fsl,data-mapping = "spwg";
       fsl,data-width = <24>;
       status = "okay";
       primary;
       display-timings {
           t_lvds: t_lvds_default {
               clock-frequency = <107991360>;
               hactive = <1280>;
               vactive = <1024>;
               hback-porch = <102>;
               hfront-porch = <100>;
               vback-porch = <20>;
               vfront-porch = <20>;
               hsync-len = <2>;
               vsync-len = <2>;
           };
       };
   };
   lvds-channel@1 {
       crtc = "ipu1-di0";
       fsl,data-mapping = "spwg";
       fsl,data-width = <24>;
       status = "okay";
       split-mode;
       display-timings {


       };
   };

   /* Kyocera
   lvds-channel@0 {
       fsl,data-mapping = "spwg";
       fsl,data-width = <18>;
       status = "okay";
       primary;
       display-timings {
           native-mode = <&timing0>;
           timing0: hsd100pxn1 {
               clock-frequency = <78939059>;
               hactive = <1280>;
               vactive = <800>;
               hback-porch = <80>;
               hfront-porch = <80>;
               vback-porch = <11>;
               vfront-porch = <12>;
               hsync-len = <2>;
               vsync-len = <2>;
           };
       };
   };*/
};

As i said, I currently just comment out the display that's not being used when I generate my DTB file.

Can anybody offer guidance on how I can break this up into two different declarations?

I plan to have U-Boot detect the current environment and set the kernel variables accordingly before booting.

Any advice or insight would be appreciated!

Thank you.

Re: Kernel FDT (3.14.28): Multiple display definitions

Carlos_Musich — Fri, 11 Nov 2016 22:10:18 GMT

Hi Bob

You can find in our BSPs that you can build dtb files for different hardware.

Please check these post: https://community.nxp.com/message/843604?commentID=843604#comment-843604

So, you can take this for reference to create different dtb for different display.

You may need a a way to identify the board you are using. so uboot can know which board is being used, this could be a gpio.

And this is an example how to write a script in u-boot bootargs to load different dtb once you identify which board is being used.

https://www.element14.com/community/community/designcenter/single-board-computers/riotboard/blog/2014/09/18/linux-on-the-riotboard-part-1-u-boot

Hope this can help you.

Regards,

Carlos

Re: Kernel FDT (3.14.28): Multiple display definitions

grim — Mon, 14 Nov 2016 17:15:13 GMT

Thanks Carlos.

I had the plan to have two separate FDTs in my back pocket. Was hoping to move forward with one FDT but I can't see how that could be done.

Thanks again. I'm moving forward with two FDTs.

i.MX ProcessorsのトピックRe: Kernel FDT (3.14.28): Multiple display definitions

Kernel FDT (3.14.28): Multiple display definitions

Re: Kernel FDT (3.14.28): Multiple display definitions

Re: Kernel FDT (3.14.28): Multiple display definitions