device tree / how to build/compile & use with u-boot to boot uImage?

[Morrison, Tom]

All,

Sorry for my ignorance here, but we have upgraded our kernel from
2.6.11.xx to 2.6.20-rcx (using a specific git-branch for the mpc85xx) 
to run on the MPC8548CDS eval board (using default options provided 
by this branch for this eval board). I successfully compiled/loaded the 
uImage, but it hangs after decompression (with root=/dev/nfs)

Also, I was told to upgrade our u-boot source code (with another git 
branch for to the mpc85xx) and successfully get to the u-boot prompt.

>From googling through the lists - it seems that I need to build a 
device tree blob and pass that device tree to the kernel in some
fashion? 

I tried to compile the default dts image (using the dtc compiler 
installed by LTIB), but it is complaining about no '/chosen' in 
the definition:

  <path>/dtc -I dts -O dtb - -o mpc8548cds.dtb -V 16 dts/mpc8548cds.dts

I've looked at the Documentation/powerpc/booting_without_of.txt, 
and this gives an explanation of the internal parts of the dts file, 
but it doesn't tell me how to practically pass it to the kernel 
from u-boot (e.g.: load to memory - and use bootm xxx yyy zzz)
 
I am pretty darn confused about this whole thing. Can anybody point me
to 
a SUCCINCT explanation of the use of a dts file (and how compile and use

with u-boot to pass to kernel)?

Tom Morrison
Principal Software Engineer


EMPIRIX 
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