SPRAD09A December   2021  – July 2022 DRA821U , DRA821U-Q1

 

  1.   Abstract
  2.   Trademarks
  3. 1Hardware and Software Required Stuff
  4. 2DRA821U Boot Mode With Fast Boot Method
  5. 3Detailed Steps
    1. 3.1 Step1: Patch and Build/Copy the u-boot
    2. 3.2 Step2: Optimizations by Switching to xSPI Boot: Copy Bootloaders to xSPI
    3. 3.3 Step 3: Optimize the DTSI by Disabling Nodes not Mandatory for Linux Boot
    4. 3.4 Step 4: Create Bootable SD Card, Switch to TinyFS
    5. 3.5 Step 5: Switch to eMMC Filesystem
    6. 3.6 Step 6: Optimizations With Bootargs
    7. 3.7 Step 7: Hijack the init
  6. 4Debug Commands
    1. 4.1 SF Probe
    2. 4.2 mmcblk
    3. 4.3 How to Check Mounted Devices?
    4. 4.4 How to Check Your Partitions?
    5. 4.5 How to Restore Your Boot Setting?
  7. 5Fast Boot Result Review
  8. 6References
  9. 7Revision History

3.7 Step 7: Hijack the init

Boot switch setting:

#EVM to set xSPI Boot Mode

SW8[1-8]: 1000 0010

SW9[1-8]: 0011 0000

SW3[1-10]: 0111 0010 10

Commands: (Do this on the EVM)

Once you get to Linux shell prompt. Create file /home/root/init.sh with contents below:

  • #!/bin/sh
  • mount -t proc proc /proc
  • mount -n -t sysfs none /sys
  • mount -n -t tmpfs none /run
  • echo "entering init script"
  • /bin/sh

Then, do these, this is called “hijack”.

  • chmod +x init.sh
  • cd /sbin/
  • rm init
  • ln -s /home/root/init.sh init