Porting "prep" from ppc to powerpc.

Porting "prep" from ppc to powerpc.

[Rob Landley]

Is anyone already doing this?  I asked around here a few weeks ago and got the 
advice:

> In theory.. copy the files from ppc/platforms/prep.* to
> powerpc/platforms/prep/ 
> and make some Kconfigs and see what breaks :)

Unfortunately, there isn't a ppc/platforms/prep.  Under arch/ppc there's:

./boot/simple/misc-prep.c
./boot/simple/prepmap.c
./boot/utils/mkprep.c
./configs/prep_defconfig
./platforms/prep_pci.c
./platforms/prep_setup.c
./syslib/prep_nvram.c

And I'm not sure which are relevant.  Any hints?

Rob

Re: Porting "prep" from ppc to powerpc.

[David Gibson]

On Fri, May 25, 2007 at 10:38:39PM -0400, Rob Landley wrote:
> Is anyone already doing this?  I asked around here a few weeks ago and got the 
> advice:
> 
> > In theory.. copy the files from ppc/platforms/prep.* to
> > powerpc/platforms/prep/ 
> > and make some Kconfigs and see what breaks :)

Actually, I don't really recommend that method in any case.

Instead I suggest making a Kconfig under arch/powerpc, then adding
things until it builds, then adding things until it boots.  When you
need to know what has to be done at a particular point, consult
arch/ppc.

> Unfortunately, there isn't a ppc/platforms/prep.  Under arch/ppc there's:
> 
> ./boot/simple/misc-prep.c
> ./boot/simple/prepmap.c
> ./boot/utils/mkprep.c
> ./configs/prep_defconfig
> ./platforms/prep_pci.c
> ./platforms/prep_setup.c
> ./syslib/prep_nvram.c
> 
> And I'm not sure which are relevant.  Any hints?

-- 
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: Porting "prep" from ppc to powerpc.

[Rob Landley]

On Sunday 27 May 2007 7:20 pm, David Gibson wrote:
> On Fri, May 25, 2007 at 10:38:39PM -0400, Rob Landley wrote:
> > Is anyone already doing this?  I asked around here a few weeks ago and got 
the 
> > advice:
> > 
> > > In theory.. copy the files from ppc/platforms/prep.* to
> > > powerpc/platforms/prep/ 
> > > and make some Kconfigs and see what breaks :)
> 
> Actually, I don't really recommend that method in any case.
> 
> Instead I suggest making a Kconfig under arch/powerpc, then adding
> things until it builds, then adding things until it boots.  When you
> need to know what has to be done at a particular point, consult
> arch/ppc.

So study the old code until I figure out what should be in the Kconfig, 
what "things" to add for it to build, and what "things" to add until it 
boots.  And the hint as to where to start is...  study the old code.

Right.  Copying the old implementation to the new directory and debugging it 
sounded like something I might be able to do.  Starting from scratch?  Not so 
much.

Rob

Re: Porting "prep" from ppc to powerpc.

[Gabriel Paubert]

On Fri, May 25, 2007 at 10:38:39PM -0400, Rob Landley wrote:
> Is anyone already doing this?  

I'm interested but I don't have the time right now.

> I asked around here a few weeks ago and got the 
> advice:
> 
> > In theory.. copy the files from ppc/platforms/prep.* to
> > powerpc/platforms/prep/ 
> > and make some Kconfigs and see what breaks :)
> 
> Unfortunately, there isn't a ppc/platforms/prep.  Under arch/ppc there's:
> 
> ./boot/simple/misc-prep.c
> ./boot/simple/prepmap.c
> ./boot/utils/mkprep.c
> ./configs/prep_defconfig
> ./platforms/prep_pci.c
> ./platforms/prep_setup.c
> ./syslib/prep_nvram.c
> 
> And I'm not sure which are relevant.  Any hints?

I was thinking of writing a bootwrapper that would
convert residual data to flat device tree. There
is a lot of valuable information in the residual data,
like the interrupt routing (which is correct if you 
can read the spec, which is not what the code in
arch/ppc did).


	Gabriel

Re: Porting "prep" from ppc to powerpc.

[Benjamin Herrenschmidt]

On Mon, 2007-05-28 at 09:55 +0200, Gabriel Paubert wrote:
> I was thinking of writing a bootwrapper that would
> convert residual data to flat device tree. There
> is a lot of valuable information in the residual data,
> like the interrupt routing (which is correct if you 
> can read the spec, which is not what the code in
> arch/ppc did). 

We were wondering the other day how reliable the residual data are...

David Gibson's been toying with that too already, you should sync with
him. 

Cheers,
Ben.

Re: Porting "prep" from ppc to powerpc.

[Gabriel Paubert]

On Mon, May 28, 2007 at 06:23:34PM +1000, Benjamin Herrenschmidt wrote:
> On Mon, 2007-05-28 at 09:55 +0200, Gabriel Paubert wrote:
> > I was thinking of writing a bootwrapper that would
> > convert residual data to flat device tree. There
> > is a lot of valuable information in the residual data,
> > like the interrupt routing (which is correct if you 
> > can read the spec, which is not what the code in
> > arch/ppc did). 
> 
> We were wondering the other day how reliable the residual data are...
> 

On the boards I use, they are very good. And there is some information
(memory size, tb and cpu freq, etc...) that I'd rather take from the 
residual data than trying to guess.

> David Gibson's been toying with that too already, you should sync with
> him. 

I've not yet started to write anything (finishing a hardware project).

	Regards,
	Gabriel

Re: Porting "prep" from ppc to powerpc.

[Benjamin Herrenschmidt]

On Mon, 2007-05-28 at 10:46 +0200, Gabriel Paubert wrote:
> On Mon, May 28, 2007 at 06:23:34PM +1000, Benjamin Herrenschmidt wrote:
> > On Mon, 2007-05-28 at 09:55 +0200, Gabriel Paubert wrote:
> > > I was thinking of writing a bootwrapper that would
> > > convert residual data to flat device tree. There
> > > is a lot of valuable information in the residual data,
> > > like the interrupt routing (which is correct if you 
> > > can read the spec, which is not what the code in
> > > arch/ppc did). 
> > 
> > We were wondering the other day how reliable the residual data are...
> > 
> 
> On the boards I use, they are very good. And there is some information
> (memory size, tb and cpu freq, etc...) that I'd rather take from the 
> residual data than trying to guess.
> 
> > David Gibson's been toying with that too already, you should sync with
> > him. 
> 
> I've not yet started to write anything (finishing a hardware project).

Ok, well, anyway, that's good to know that they are good.

Ben.

Re: Porting "prep" from ppc to powerpc.

[Rob Landley]

On Monday 28 May 2007 3:55 am, Gabriel Paubert wrote:
> On Fri, May 25, 2007 at 10:38:39PM -0400, Rob Landley wrote:
> > Is anyone already doing this?  
> 
> I'm interested but I don't have the time right now.

I'm interested but don't have the expertise.

I don't have prep documentation, I'm not familiar with the internals of the 
powerpc architecture (beyond the endianness/word size/alignment checklist for 
porting userspace programs from arch to arch), I know just enough about Open 
Firmware to really dislike it, and I don't actually have prep hardware.  I do 
have qemu, but it doesn't actually work even with the old ARCH=ppc prep 
kernels.  It segfaults trying to decompress them.

I was hoping to use a prep kernel to debug qemu, but my build system (which 
already builds several other architecutres from the same script) can't do 
ARCH=ppc because that doesn't understand "make headers_install", so I have to 
build them by hand supplying different architectures at different steps of 
the process.  Which puts it waaaaay down on my todo list.

Fixing the Linux build system to actually work for prep would be nice, but it 
sounds like teaching ARCH=ppc to do "make headers install" would be a couple 
orders of magnitude easier...

Rob

Re: Porting "prep" from ppc to powerpc.

[Benjamin Herrenschmidt]

On Tue, 2007-05-29 at 17:02 -0400, Rob Landley wrote:
> I know just enough about Open 
> Firmware to really dislike it,

You need to learn more or fix your taste :-)

Ben.