• Hardware:
  • TI DRA821U EVM
• Software
  • J7200XSOMXEVM
  • Linux SDK version: ti-processor-sdk-linux-j7200-evm-08_00_00_05
  • RTOS SDK version: ti-processor-sdk-rtos-j7200-evm-08_00_00_12

Regarding how to build the Linux/RTOS for DRA821U, see the Understanding bootloaders in Processor SDK J7200 (RTOS/Linux) section.

Regarding how to set up the EVM to test, see the Jacinto7 DRA821 Evaluation Module (EVM) User's Guide.

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

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.

The process is broken down into seven steps. Follow the steps exactly.

• Step1: patch and build / copy the u-boot onto your SD card “Boot Partition”.
• Step2: Optimize boot time by switching to xSPI boot, so we copy the bootloaders from SD card onto xSPI Flash.
• Step3: Optimize the device tree by disabling nodes not mandatory for Linux Boot.
• Step4: Create bootable SD card, and Switch to TinyFS.
• Step5: Switch to eMMC TinyFS filesystem (Very important step!!)
• Step6: Optimizations with bootargs in the uboot.
• Step7: Hijack the init.

Understand this:

• When a brand new SD card that has never be formatted is used: Following this sequence:
  • Step4 > step1 > step2 > step3 > step5 > step6 > step7
• If using a DRA821 bootable SD card follow the below sequence:
  • Step1 > step2 > step3 > step4 > step5 > step6 > step7

Regarding the boot switch jumper setting on the DRA821U EVM, see Table 3-1.

There are boot switches need to be matched correctly in each step as shown above. Two boot switch settings are summarized in this document: one is the SD card switch and one is the xSPI switch.

In the step2:

• The SD card to boot is used
• Perform some actions that is copying the uboot onto xSPI flash.
• Switch to the xSPI flash.

The switch setting in each step should be marked.

Assume you are familiar with TI Jacinto SDK build setting up. Make sure your NB is connecting to the network while building. Because the uboot might referencing the ti github. The working copy cmd is as this, you need to change according the red parameters (root).

Boot Switch setting:

This step is no needing to touch the boot switch on the EVM.

Patches:

• 01 - Remove-prints-to-optimize-U-Boot-time.patch (this patch is here: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1105700/dra821u-application-note-how-to-linux-fast-boot-on-dra821u-putting-the-required-2-patches-here)

Cmds: (Do this on ubuntu, not the EVM)

cd $PSDKLA/board-support/u-boot-2021.01+gitAUTOINC+53e79d0e89-g53e79d0e89/
git am 0001-Remove-prints-to-optimize-U-Boot-time.patch
cd ../..
make u-boot

cp board-support/k3-image-gen-2021.05/tiboot3.bin board-support/u-boot_build/a72/tispl.bin board-support/u-boot_build/a72/u-boot.img /media/root/boot/