~~tag>Edge2 boot-sequence~~
====== Edge2 boot sequence ======

Edge2 have advanced and flexible boot possibilities 

===== Common boot process =====

[[#SPL-loader]] => [[#U-Boot-loader]] => [[#OOWOW-special-mode]] => [[#U-Boot-OS-boot-sequence]] => [[#OOWOW-rescue-mode]]

===== SPL loader =====

  * SPL-loader is a 1st boot-loader which can start from ''SPI-Flash'' => ''eMMC'' => ''SD'' card. By default its start from ''SPI-flash''.
  * SPL-loader scan special areas for next [[#U-Boot-loader]] by ''SD'' => ''eMMC'' => ''SPI-FLash'' 

<tabbox common logs>

```log spl-boot-example.log
U-Boot SPL board init
U-Boot SPL 2017.09 (Aug 26 2022 - 15:50:37)
MCU: bootmode: 1, oowow 0
board_boot_order: /chosen found, using spl_boot_device()
!!! same-as-spl: 
!!! /mmc@fe2c0000: 
!!! /mmc@fe2e0000: 
!!! /spi@fe2b0000/flash@1: 
Trying to boot from MMC2 :: 0
Card did not respond to voltage select!
Trying to boot from MMC1 :: 1
Trying fit image at 0x4000 sector
Not fit magic
Trying fit image at 0x5000 sector
Not fit magic
Trying to boot from MTD2 :: 2
Trying fit image at 0x300 sector
...
```

<tabbox oowow-mode logs >

```log log spl-boot-oowow-mode-example.log
U-Boot SPL board init
U-Boot SPL 2017.09 (Aug 26 2022 - 15:50:37)
MCU: bootmode: 1, oowow 1
MCU: oowow 2
board_boot_order: /chosen found, using spl_boot_device()
!!! same-as-spl: 
+++ /spi@fe2b0000/flash@1: 
!!! /mmc@fe2c0000: 
!!! /mmc@fe2e0000: 
!!! /spi@fe2b0000/flash@1: 
Trying to boot from MTD2 :: 0
Trying fit image at 0x300 sector
...
Jumping to U-Boot(0x00200000) via ARM Trusted Firmware(0x00040000)
...
```

</tabbox>


===== U-Boot loader =====

WIP:

==== U-Boot OS boot sequence ====

<WRAP important >
We discribe only about SPI-flash u-boot, for other custom U-boots which can stored at eMMC or SD its will be different 
</WRAP>

OS booting follow by ''distro_bootcmd'' which use ''boot_targets'' priority for scanning bootable OS. Step by step scan all available storage's and partitions for [[#os-boot-configuration-extlinux-config]]

```shell
kedge2# printenv boot_targets 
boot_targets=usb0 mmc1 mmc0 pxe dhcp fail
```


WIP:

==== OS boot configuration - extlinux config ====

Basic example:

```conf extlinux/extlinux.conf 
menu background /logo.bmp
LABEL Default
  LINUX /Image
  INITRD /initrd.img
  FDTDIR /dtb
  APPEND ${bootargs} earlycon=uart8250,mmio32,0xfeb50000 console=ttyFIQ0 console=tty0 irqchip.gicv3_pseudo_nmi=0 root=LABEL=ROOTFS rootflags=data=writeback rw rootfstype=ext4
timeout  10
default Default
```

===== OOWOW mode =====

OOWOW mode can be activated by

  * special on board short-cuts ''FUNCTION'' + ''RESET''
  * under running OS via special [[#MCU-register-for-start-oowow]] - software way    
WIP:


==== OOWOW special mode ====

WIP:

==== OOWOW rescue mode ====

WIP:

==== MCU register for start oowow ====

WIP: