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products:sbc:vim4:configurations:device-tree-overlay

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products:sbc:vim4:configurations:device-tree-overlay [2022/07/06 03:51]
nick 		products:sbc:vim4:configurations:device-tree-overlay [2022/09/28 08:45] (current)
nick
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-====== Device Tree Overlay ======+{{indexmenu_n>5}}
  
-===== Introduction ===== 
  
-You can use Device Tree Overlay feature to enable/disable some hardware functions without to recompile the kernel source code.+====== VIM4 Device Tree Overlay ======
  
-The dtbo files are stored in directory ''/boot/dtb/amlogic/kvim4.dtb.overlays'': 
  
-``` +{{page>products:sbc:common:configurations:device-tree-overlay&noheader}}
-khadas@Khadas:~$ ls -al /boot/dtb/amlogic/kvim4.dtb.overlays/ +
-total 28 +
-drwxr-xr-x 2 root root 4096 Jul  6 14:55 . +
-drwxr-xr-x 3 root root 4096 Jul  6 14:55 .. +
--rwxr-xr-x 1 root root  462 Jul  6 14:55 ext_board.dtbo +
--rwxr-xr-x 1 root root  223 Jul  6 14:55 i2cm_a.dtbo +
--rwxr-xr-x 1 root root  223 Jul  6 14:55 i2cm_f.dtbo +
--rwxr-xr-x 1 root root  225 Jul  6 14:55 pwm_f.dtbo +
--rwxr-xr-x 1 root root  225 Jul  6 14:55 uart_e.dtbo +
-``` +
- +
-The releated dtbo configuration file is ''/boot/dtb/amlogic/kvim4.dtb.overlay.env'' +
- +
-``` +
-khadas@Khadas:~$ ls /boot/dtb/amlogic/kvim4.dtb.overlay.env  +
-/boot/dtb/amlogic/kvim4.dtb.overlay.env +
-``` +
- +
-===== Configuration ===== +
- +
-If you want to enable some functions, you can edit the dtbo configuration file ''/boot/dtb/amlogic/kvim4.dtb.overlay.env'' and add the dtbo name to node ''fdt_overlays''. +
- +
-For example, if you want to enable ''I2CM_F'', you can edit ''/boot/dtb/amlogic/kvim4.dtb.overlay.env'' and add ''i2cm_a'' to node ''fdt_overlays''. +
- +
-``` +
-khadas@Khadas:~$ cat /boot/dtb/amlogic/kvim4.dtb.overlay.env  +
-fdt_overlays=i2cm_a +
-``` +
- +
-Save the file and reboot the system to take effect. +
- +
-===== Make Your Own DTBO Files ===== +
- +
-There are some ready to use dtbo files, you can also add your own dtbos to enable or disable the peripherals. +
- +
- +
-  * Write your own device tree overlay file, for example ''example.dts'': ``` +
-/dts-v1/; +
-/plugin/; +
- +
-/ { +
-    fragment@0 { +
-        target = <&i2c5>; +
- +
-        __overlay__ { +
-            status = "okay"; +
-        }; +
-    }; +
-}; +
-```  +
- +
-This device tree overlay is to enable ''i2c3''. +
- +
-  * Compile it to dtbo ``` +
-khadas@Khadas:~$ dtc -I dts -O dtb -o example.dtbo example.dts +
-khadas@Khadas:~$ ls example.dtbo +
-example.dtbo +
-``` +
- +
-  * Copy the dtbo file to ''/boot/dtb/amlogic/kvim4.dtb.overlays/'' +
- +
-  * Edit ''/boot/dtb/amlogic/kvim4.dtb.overlay.env'' to add in node ''fdt_overlays'' and save the file. +
- +
-  * Reboot the board+
Last modified: 2022/07/06 03:51 by nick

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