Fix/Debug Pogoplug v4 arch linux boot failure

Recently, after upgrade archlinux on Pogo, system failed to boot up.
Even fresh install can't fix this problem.

required:
netconsole uboot installed on pogoplug v4.


Debug:
1.  setup netconsole and monitor uboot :
xterm1: nc -l -u -p 6666
xterm2: nc -u 192.168.1.10 6666

looks like kernel booted successfully.

2. printenv in uboot
Pogov4>  printenv
arcNumber=3960
baudrate=115200
bootcmd=run bootcmd_usb; run bootcmd_mmc; run bootcmd_sata; run bootcmd_pogo; reset
bootcmd_mmc=run mmc_init; run set_bootargs_mmc; run mmc_boot
bootcmd_pogo=if ubi part root 2048 && ubifsmount ubi:rootfs && ubifsload 0x800000 uboot.mtd0.dockstar.original.kwb ; then go 0x800200; fi
bootcmd_sata=run sata_init; run set_bootargs_sata; run sata_boot;
bootcmd_usb=run usb_init; run set_bootargs_usb; run usb_boot;
bootdelay=10
console=ttyS0,115200
device=0:1
ethact=egiga0
ethaddr=00:25:31:05:08:2e
if_netconsole=ping $serverip
ipaddr=192.168.1.10
led_error=orange blinking
led_exit=green off
led_init=green blinking
machid=F78
mainlineLinux=yes
mmc_boot=mw 0x800000 0 1; run mmc_load_uimage; if run mmc_load_uinitrd; then bootm 0x800000 0x1100000; else bootm 0x800000; fi
mmc_init=mmc rescan
mmc_load_uimage=ext2load mmc $device 0x800000 /boot/uImage
mmc_load_uinitrd=ext2load mmc $device 0x1100000 /boot/uInitrd
mmc_root=/dev/mmcblk0p1
mtdids=nand0=orion_nand
mtdparts=mtdparts=orion_nand:2M(u-boot),3M(uImage),3M(uImage2),8M(failsafe),112M(root)
ncip=192.168.1.100
partition=nand0,2
preboot=run if_netconsole start_netconsole
preboot_nc=run if_netconsole start_netconsole
rootdelay=10
rootfstype=ext3
sata_boot=mw 0x800000 0 1; run sata_load_uimage; if run sata_load_uinitrd; then bootm 0x800000 0x1100000; else bootm 0x800000; fi
sata_init=ide reset
sata_load_uimage=ext2load ide $device 0x800000 /boot/uImage
sata_load_uinitrd=ext2load ide $device 0x1100000 /boot/uInitrd
sata_root=/dev/sda1
serverip=192.168.1.100
set_bootargs_mmc=setenv bootargs console=$console root=$mmc_root rootdelay=$rootdelay rootfstype=$rootfstype $mtdparts
set_bootargs_sata=setenv bootargs console=$console root=$sata_root rootdelay=$rootdelay rootfstype=$rootfstype $mtdparts
set_bootargs_usb=setenv bootargs console=$console root=$usb_root rootdelay=$rootdelay rootfstype=$rootfstype $mtdparts
start_netconsole=setenv ncip $serverip; setenv bootdelay 10; setenv stdin nc; setenv stdout nc; setenv stderr nc; version;
stderr=nc
stdin=nc
stdout=nc
usb_boot=mw 0x800000 0 1; run usb_load_uimage; if run usb_load_uinitrd; then bootm 0x800000 0x1100000; else bootm 0x800000; fi
usb_init=usb start
usb_load_uimage=ext2load usb $device 0x800000 /boot/uImage
usb_load_uinitrd=ext2load usb $device 0x1100000 /boot/uInitrd
usb_root=/dev/sda1
usb_rootfstype=ext3

Environment size: 2468/131068 bytes
Pogov4>

3. Enable netconsole for linux kernel
Pogov4> setenv set_bootargs_mmc 'setenv bootargs root=$mmc_root rootdelay=$rootdelay rootfstype=$rootfstype $mtdparts [email protected]/,[email protected]/'
Pogov4> saveenv

4. continue monitor linux kernel netconsole output
OUTPUT INDICATE NEW KERNEL NEED EXT4 ROOTFS!

5. fix pogo by format SD card with mkfs.ext4 -j /dev/sdb1, then fresh tar -xvzf Archlinux -C /mnt/alarm

6. retry and monitor kernel netconsole output
STILL REPORT NEED EXT4 ROOTFS

7. set uboot parameter:
Pogov4>setenv rootfstype ext4
Pogov4> saveenv

8. retry reboot
BOOT SUCCESS!

7. close kernel netconsole and change bootargs back to normal.
Pogov4> setenv set_bootargs_mmc 'setenv bootargs console=$console root=$mmc_root rootdelay=$rootdelay rootfstype=$rootfstype $mtdparts'
Pogov4> saveenv

NOW MY UBOOT ENV:
arcNumber=3960
baudrate=115200
bootcmd=run bootcmd_usb; run bootcmd_mmc; run bootcmd_sata; run bootcmd_pogo; reset
bootcmd_mmc=run mmc_init; run set_bootargs_mmc; run mmc_boot
bootcmd_pogo=if ubi part root 2048 && ubifsmount ubi:rootfs && ubifsload 0x800000 uboot.mtd0.dockstar.original.kwb ; then go 0x800200; fi
bootcmd_sata=run sata_init; run set_bootargs_sata; run sata_boot;
bootcmd_usb=run usb_init; run set_bootargs_usb; run usb_boot;
bootdelay=10
console=ttyS0,115200
device=0:1
ethact=egiga0
ethaddr=00:25:31:05:08:2e
if_netconsole=ping $serverip
ipaddr=192.168.1.10
led_error=orange blinking
led_exit=green off
led_init=green blinking
machid=F78
mainlineLinux=yes
mmc_boot=mw 0x800000 0 1; run mmc_load_uimage; if run mmc_load_uinitrd; then bootm 0x800000 0x1100000; else bootm 0x800000; fi
mmc_init=mmc rescan
mmc_load_uimage=ext2load mmc $device 0x800000 /boot/uImage
mmc_load_uinitrd=ext2load mmc $device 0x1100000 /boot/uInitrd
mmc_root=/dev/mmcblk0p1
mtdids=nand0=orion_nand
mtdparts=mtdparts=orion_nand:2M(u-boot),3M(uImage),3M(uImage2),8M(failsafe),112M(root)
ncip=192.168.1.100
partition=nand0,2
preboot=run if_netconsole start_netconsole
preboot_nc=run if_netconsole start_netconsole
rootdelay=10
rootfstype=ext3
sata_boot=mw 0x800000 0 1; run sata_load_uimage; if run sata_load_uinitrd; then bootm 0x800000 0x1100000; else bootm 0x800000; fi
sata_init=ide reset
sata_load_uimage=ext2load ide $device 0x800000 /boot/uImage
sata_load_uinitrd=ext2load ide $device 0x1100000 /boot/uInitrd
sata_root=/dev/sda1
serverip=192.168.1.100
set_bootargs_mmc=setenv bootargs console=$console root=$mmc_root rootdelay=$rootdelay rootfstype=$rootfstype $mtdparts
set_bootargs_sata=setenv bootargs console=$console root=$sata_root rootdelay=$rootdelay rootfstype=$rootfstype $mtdparts
set_bootargs_usb=setenv bootargs console=$console root=$usb_root rootdelay=$rootdelay rootfstype=$rootfstype $mtdparts
start_netconsole=setenv ncip $serverip; setenv bootdelay 10; setenv stdin nc; setenv stdout nc; setenv stderr nc; version;
stderr=nc
stdin=nc
stdout=nc
usb_boot=mw 0x800000 0 1; run usb_load_uimage; if run usb_load_uinitrd; then bootm 0x800000 0x1100000; else bootm 0x800000; fi
usb_init=usb start
usb_load_uimage=ext2load usb $device 0x800000 /boot/uImage
usb_load_uinitrd=ext2load usb $device 0x1100000 /boot/uInitrd
usb_root=/dev/sda1
usb_rootfstype=ext3

AND using ext4 -j for linux root.