How the Hikey960 is starting up?

I’ve checked all the information in this site but haven’t found the answer on my question.
How this board is booted?
From which address CPU starts to execute the code? I cannot find Kirin960 datasheet with boot process.
Could someone describe the boot flow in details?
I’m not asking for source code of mysterious sec_usb_xloader.img, sec_uce_boot.img, sec_fastboot.img.
I’m just asking why do we need them and how they are used?

Just to start I’ll start from the recovery process of a Hikey960.
As I currently understand, the boot process flows like that:

  • When we call “./hikey_idt -c ./config -p /dev/ttyUSB0” executable file “./hikey_idt” opens “/dev/ttyUSB0” and sends binaries from “./config” file into specified addressed, described inside of this file. Now we’re working with some USB/UART native bootloader (which is located NOT in UFS), which is inside of the silicon.
  • The content of the “./config” file:
    ./sec_usb_xloader.img 0x00020000
    ./sec_uce_boot.img 0x6A908000
    ./sec_fastboot.img 0x1AC00000
  • As I understand, recovery inbuilt USB/TTY bootloader places “./sec_usb_xloader.img” starting from “0x00020000” address (UFS or/and RAM?) and starts it from this address. This is the 2nd bootloader.
  • 2nd bootloader loads “./sec_uce_boot.img” starting from “0x6A908000” address (UFS or/and RAM?) which is 3rd bootloader.
  • 3rd bootloader loads “./sec_fastboot.img” starting from “0x1AC00000” address (UFS or/and RAM?) which is 4th bootloader. Now we’re doing what we want with fastboot.

P.S. Also I understand, that at some stages we need to set up operations with SRAM/DRAM/UFS and this is done during described boot flow. Without source codes or documentation it is really difficult to understand. Could someone extend this hypothetical boot scenarios?

I will appreciate any answers!

These addresses are either physical RAM addresses or some virtual RAM mapping set by the initial ROM code. The UFS is used as a SCSI disk split into 4 blocks: sda for the xloader, sdb is empty, sdc is reserved for some weird android anti-recovery stuff, and sdd is the “real” hard disk, where you flash the partition table and use other partitions. This UFS structure is inherited from/by other modern huawei phones like Mate9, and is probably completely redundant if you just want to run debian
on this board without any androidisms.

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