There are lot of howtos written for this topic but most won't worked for me. Irky's howto is very good. I'm mirroring his files here and summarise his howto. If you have any question look into his article.

The dockstar is special device, because it does not support serial boot like other Marvel kirkwood devices. E.g. when you bricked a Seagate GoFlex you can recover it without jtag over serial boot. What is serial boot? Recover without jtag

This howto is for the Seagate Dockstar tested on archlinux with openocd 0.8!

You need only a buspirate with a jtag firmware, no serial is needed here.

Steps

• Download buspirate.cfg dockstar.cfg uboot.j.kwb
• change ttyUSB1 to your buspirate interface in buspirate.cfg
• connect buspirate to the dockstar Dockstar pinout Buspirate pinout
• power the dockstar
• openocd -f dockstar.cfg
• telnet localhost 4444
• enter "halt" into telnet session but don't hit enter
• press reset button and very shortly after press enter into telnet session
• when openocd shows "target halted in ARM state due to debug-request, current mode: Supervisor" everything is good
• when openocd shows "target halted in Thumb state due to debug-request, current mode: Supervisor" repeat halt + reset procedure
• telnet: sheevaplug_init
• telnet: nand probe 0
• telnet: nand erase 0 0x0 0xa0000
• telnet: nand write 0 uboot.j.kwb 0 oob_softecc_kw
• wait ~15 minutes
• openocd shows a success message