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

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)=20
to run on the MPC8548CDS eval board (using default options provided=20
by this branch for this eval board). I successfully compiled/loaded the=20
uImage, but it hangs after decompression (with root=3D/dev/nfs)

Also, I was told to upgrade our u-boot source code (with another git=20
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=20
device tree blob and pass that device tree to the kernel in some
fashion?=20

I tried to compile the default dts image (using the dtc compiler=20
installed by LTIB), but it is complaining about no '/chosen' in=20
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,=20
and this gives an explanation of the internal parts of the dts file,=20
but it doesn't tell me how to practically pass it to the kernel=20
from u-boot (e.g.: load to memory - and use bootm xxx yyy zzz)
=20
I am pretty darn confused about this whole thing. Can anybody point me
to=20
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=20
20 Crosby Drive - Bedford, MA  01730
p: 781.266.3567 f: 781.266.3670=20
email: tmorrison@empirix.com=20
www.empirix.com

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

[Ben Warren]

Tom,

I feel your pain.

On Fri, 2007-02-09 at 16:55 -0500, Morrison, Tom wrote:
> All,
> 

> 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)?
> 

u-boot> bootm <kernel_address> <initrd_address> <dtb_address>

If you don't have an initrd, it's

u-boot> bootm <kernel_address> - <dtb_address>

Hope that's succinct enough.

Ben

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

[Jerry Van Baren]

Morrison, Tom wrote:
> 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

Trivia: the no "/chosen" warning can be ignored.  The u-boot command 
"bootm" generates the "/chosen" branch when you run the command and it 
boots linux.

Note: You want version 16 (or better?) for the fdt blob.  I believe the 
dtc defaults to this now, but it wasn't always that way.

[snip - others have chimed in]

> Tom Morrison
> Principal Software Engineer

gvb

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

[David Gibson]

On Fri, Feb 09, 2007 at 05:25:51PM -0500, Jerry Van Baren wrote:
> Morrison, Tom wrote:
> > 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
> 
> Trivia: the no "/chosen" warning can be ignored.  The u-boot command 
> "bootm" generates the "/chosen" branch when you run the command and it 
> boots linux.
> 
> Note: You want version 16 (or better?) for the fdt blob.  I believe the 
> dtc defaults to this now, but it wasn't always that way.

Actually you want version 17 - just as soon as I get around to
implementing that in dtc.  v16 and v17 have no differences that the
kernel looks at though, so it doesn't really matter.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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

[Grant Likely]

On 2/9/07, Morrison, Tom <tmorrison@empirix.com> wrote:
> All,
>
> 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

Add the -f flag to ignore the warning.  It's bogus for what you're doing.

u-boot adds the chosen node at runtime.

g.

-- 
Grant Likely, B.Sc. P.Eng.
Secret Lab Technologies Ltd.
grant.likely@secretlab.ca
(403) 399-0195

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

[David Gibson]

On Fri, Feb 09, 2007 at 03:37:45PM -0700, Grant Likely wrote:
> On 2/9/07, Morrison, Tom <tmorrison@empirix.com> wrote:
> > All,
> >
> > 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
> 
> Add the -f flag to ignore the warning.  It's bogus for what you're
> doing.

Yeah, I really need to rework dtc's warnings and error messages, it's
much too keen to complain at the moment.  I just haven't had the time,
yet.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson