How does FSBL load the FreeRTOS on the small core and execute it?

Duo
1

Hi all,
I’m excited to see that the small core now can run FreeRTOS.

As mentioned in Duo firmware v1.0.5, it says:

  • FSBL itself already supports dual-core startup, and you can use kernel remoteproc to start the small core’s ELF.
  • BL2 will first load the FreeRTOS binary from the flash into memory and start the small core. After that, BL2 loads OpenSBI/U-Boot/Kernel to run on the big core.

I followed this post Milk-v Duo Compilation Process Part II- Compiling Small Core FreeRTOS, which explains quite detailed info how FreeRTOS is built, to trace the symbols defined for FreeRTOS, such as BLCP_2ND_RUNADDR is the address to run on the small core.

However, I get stuck at FSBL stage because I could not find any source code that let FSBL load FreeRTOS image cvirtos.bin to BLCP_2ND_RUNADDR and wake up the small core.

In Duo Buildroot SDK, FSBL is almost pre-built, when I refer to duo-buildroot-sdk/fsbl/plat/cv180x/bl2/bl2_main.c at develop · milkv-duo/duo-buildroot-sdk · GitHub, only init_comm_info() function is related to FreeRTOS.

So, I have few questions, please kindly guide me on them:

  • Where can I get the full source to to understand how BL2 load the FreeRTOS and wake up the small core?
  • Is there any document should I look at for better understaning the boot up of dual-core system?
5 Likes
2

i’d like to know the answers too!

2 Likes
3

Please refer to [v2,2/2] package/milkv-duo: add packages for milkv-duo - Patchwork (ozlabs.org), where the series of patches submitted to buildroot indicate how the freertos is built.

And FYI [v2,1/2] configs/milkv_duo: new defconfig - Patchwork (ozlabs.org), the post-image.sh clearly tells how fip.bin integrates the freertos’s binary file.

I hope the sdcard image building process of the buildroot is more clear than the official sdk.