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

2 DRA821U Boot Mode With Fast Boot Method

Figure 2-1 shows the current Linux boot flow with the SDK.

GUID-20211124-SS0I-D2C7-RMWN-XL9TXDJBTH8P-low.png Figure 2-1 Jacinto DRA821U Linux Boot Flow

R5 SPL --> A72 ATF --> A72 SPL --> A72 U-Boot --> A72 Linux.

In the above boot flow each phase is optimized to achieve faster boot time:

  • Optimize U-Boot to remove UART prints.
  • Enable only the peripherals that are mandatory for booting Linux and disable the rest.
  • Switch to booting from xSPI instead booting from SD card.
  • Switch to file system in eMMC as against using SD card for hosting the file system.

The time spent in booting to Linux kernel is approximately 3 Seconds.