To update bootloader / kernel / devicetree in a running system you have to copy the images in your tftp directory and upload them to the eMMC or SD Card.

Please see How to setup TFTP Server

1. Boot from eMMC or SD and stop autoboot in U-Boot

Hit any key to stop autoboot:  0
=>

2. Set U-Boot variable mmcdev according to the drive you want to write to

=> setenv mmcdev <Nr.>

mmcdev

3. Connect device via ethernet to a tftp server supplying the image
4. Provide the correct network configuration in U-Boot:

• ⇒ setenv autoload no
• ⇒ setenv serverip <serverip> (e.g.: setenv serverip 192.168.100.110)
• ⇒ setenv ipaddr <ipaddr> (e.g.: setenv ipaddr 192.168.100.111)
• ⇒ setenv netmask <netmask> (e.g.: setenv netmask 255.255.255.0)

5. Provide U-Boot the file name of the desired image on the tftp server:

• For U-Boot update:
  
  TQMa6x, TQMa6ULx, TQMa7x, TQMLS102xA:
  ⇒ setenv uboot <filename>
  
  TQMa335x: please see Updating the firmware
  
  
• For Device Tree update:
  
  TQMa6x, TQMa6ULx, TQMa7x, TQMLS102xA:
  ⇒ setenv fdt_file <filename>
  
  TQMa335x: please see Updating the firmware
  
  
• For Kernel update:
  
  TQMa6x, TQMa6ULx, TQMa7x, TQMLS102xA:
  ⇒ setenv zimage <filename>
  
  TQMa335x: please see Updating the firmware
  
  

6. Perform Update:

• U-Boot update:
  TQMa6x, TQMa6ULx, TQMa7x, TQMLS102xA:
  ⇒ run update_uboot
  
  TQMa335x: please see Updating the firmware
  
  
• Device Tree update:
  TQMa6x, TQMa6ULx, TQMa7x, TQMLS102xA:
  ⇒ run update_fdt
  
  TQMa335x: please see Updating the firmware
  
  
• Kernel update:
  TQMa6x, TQMa6ULx, TQMa7x, TQMLS102xA:
  ⇒ run update_kernel
  
  TQMa335x: please see Updating the firmware