1. Execute the commands to reconfig the kernel
# cd kernel
# make ARCH=arm64 menuconfig
2. After reconfig, rename the file kernel\.config to rockchip_linux_defconfig
3. Copy the file kernel\rockchip_linux_defconfig to replace kernel\arch\arm64\configs\rockchip_linux_defconfig

It is recommended to back up the original rockchip_linux_defconfig before replacing.
 

eg. Switch HDMI to MIPI LCD (Debian11)

Config files path: k356x_linux5.10\kernel\arch\arm64\boot\dts\rockchip\

1. open the file rk3566-evb2-lp4x-v10-linux.dts with an editor. Comment HDMI, uncomment MIPI and save:
//#include "rk3566-evb2-lp4x-v10_hdmi.dtsi"
#include "rk3566-evb2-lp4x-v10_mipi.dtsi"
2. recompile kernel
3. reflash kernel to the board.
 

I downloaded the source code，when I try to compile, I got this error:

  @ubuntu:~/rk356x_linux5.10$  ./build.sh kernel

  processing option: kernel

  ============Start building kernel============

  TARGET_ARCH     =arm64
  TARGET_KERNEL_CONFIG =rockchip_linux_defconfig
  TARGET_KERNEL_DTS   =rk3566-evb2-lp4x-v10-linux
  TARGET_KERNEL_CONFIG_FRAGMENT =

  ==========================================

  #
  # No change to .config
  #
    CALL    scripts/atomic/check-atomics.sh
    CALL    scripts/checksyscalls.sh
    CHK    include/generated/compile.h
    LZ4C    arch/arm64/boot/Image.lz4

  Incorrect parameters
  Usage :
        lz4 [arg] [input] [output]
  input   : a filename
        with no FILE, or when  FILE is - or stdin, read standard input

  Arguments :

   -1   : Fast compression (default)
   -9   : High compression
   -d   : decompression (default for .lz4 extension)
   -z   : force compression
   -f   : overwrite output without prompting
   -h/-H  : display help/long help and exit
  arch/arm64/boot/Makefile:31: recipe for target 'arch/arm64/boot/Image.lz4'  failed

  make[2]: *** [arch/arm64/boot/Image.lz4] Error 1
  make[2]: *** Deleting file 'arch/arm64/boot/Image.lz4'
  arch/arm64/Makefile:170: recipe for target 'Image.lz4' failed
  make[1]: *** [Image.lz4] Error 2
  make[1]: *** Waiting for unfinished jobs....
  arch/arm64/Makefile:214: recipe for target 'rk3566-evb2-lp4x-v10-linux.img'  failed
  make: *** [rk3566-evb2-lp4x-v10-linux.img] Error 2
  ERROR: Running build_kernel failed!
  ERROR: exit code 2 from line 663:
      make ARCH=$RK_ARCH $RK_KERNEL_DTS.img -j$RK_JOBS
    

Cause: The version of lz4 delivered with the compilation system is too early.
Solution: update to V1.8.3 or later.
lz4 -v            //check the compiler lz4 version
sudo cp out/host/linux-x86/bin/lz4 /usr/bin/lz   //copy lz4 from the Android source directory to override the compiler's

Camera does not work properly on board with more than 4GB of memory. After the memory is upgraded from 4GB to 8GB, open the camera APP, the terminal will output:

[  100.488782] rga_mm: RGA_MMU unsupported Memory larger than 4G!
[  100.488814] rga_mm: scheduler core[4] unsupported mm_flag[0x0]!
[  100.488821] rga_mm: rga_mm_map_buffer map dma_buf error!
[  100.488826] rga_mm: job buffer map failed!
[  100.488831] rga_mm: dst channel map job buffer failed!
[  100.488834] rga_mm: failed to map buffer
[  100.488842] rga_job: rga_job_commit: failed to map job info
[  100.488896] rga_job: request[1] task[0] job_commit failed.
[  100.488909] rga_job: rga request commit failed!
[  100.488915] rga: request[1] submit failed!

Solution: Modify the source code according to the file ddr_than-4G.patch and compile it again.