Does offset mean, it starts reading at 0x100000 and everything is dealigned by this value?
Yes. On 0 - 0x100000 u-boot and it's environment are located.
Can I change the boot script where it says 'kernel_start=0x100000' to a correct value and how?
When you look at the environment you see
bootcmd=run loadzimage; run loadinitrd; run mk_mtdparts; setenv bootargs $(console) $(bootargs_root) $(bootargs_end) $(mtdparts); bootm 0x40000 0x900000
This is the bootscript. It runs loadzimage, then it runs loadinitrd, then it runs mk_mtdparts, then it sets bootargs, and finally it executes the image on 0x40000, with 0x900000 as param.
So what actually is executed:
loadzimage=nand read.e 0x40000 $(kernel_start) $(kernel_size)
loadinitrd=nand read.e 0x900000 $(initrd_start) $(initrd_size)
mk_mtdparts=setenv mtdparts mtdparts=nand_mtd:0x80000@0(uboot),0x20000@0xa0000(env),0x20000@0xc0000(env2),$(kernel_size)@$(kernel_start)(uImage),$(initrd_size)@$(initrd_start)(initrd),0x3f800000@0x800000(boot),1024m@0x0(flash)
setenv bootargs $(console) $(bootargs_root) $(bootargs_end) $(mtdparts)
bootm 0x40000 0x900000
And now I see my remark about the kernel_start was wrong. The kernel is loaded from
flash offset $(kernel_start) to
0x40000. So that is OK.
At the moment the device doesn't even recognize when I press the reset button. It wont even try to load something from usb...
That is normal. Pressing of the reset button is detected by a script in initrd, which then searches for connected usb devices. When the kernel doesn't boot this ain't gonna work.
Any idea, how I can set everything back to a state where everything behaves normally and the kernel is loaded properly? USB, tftp... every method would be fine!
No sorry. As far as I can see the box should just boot. Are you *very* sure you have the right kernel? And also, the baudrate you are using is 115200?