looking for documentation on porting Linux to PowerPC platforms

looking for documentation on porting Linux to PowerPC platforms

[Abraham vd Merwe]

Hi!

Is there a document somewhere describing the basics about the PowerPC
platform and Linux, i.e.

a) how to boot linux (can I just branch to the the address where I loaded t
he
image into ram or do I need to setup registers / data structures beforehand?)

b) where/what do I change if I want to add a "sub" architecture?

I've got a ICP-PPC PowerPC backplane type system here which I want to get
Linux on. It has the MPC8240 CPU on it which from what I read is pretty much
the same as the 8260, 8245, etc. (they're all based on the 603e core right?)

Now, if I select "8xx" in menuconfig, I get another selection of machine
types (RPX-Lite, RPX-Classic, etc.). Obviously I need to own my own machine
type here, but how do I do that. Also, how does these machine types differ?
Just different peripherals? Do they have anything in common (e.g. uart).

--

Regards
 Abraham

love, v.:
	I'll let you play with my life if you'll let me play with yours.

__________________________________________________________
 Abraham vd Merwe - 2d3D, Inc.

 Device Driver Development, Outsourcing, Embedded Systems

  Cell: +27 82 565 4451         Snailmail:
   Tel: +27 21 761 7549            Block C, Aintree Park
   Fax: +27 21 761 7648            Doncaster Road
 Email: abraham@2d3d.co.za         Kenilworth, 7700
  Http: http://www.2d3d.com        South Africa

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Re: looking for documentation on porting Linux to PowerPC platforms

[Abraham vd Merwe]

Hi Chris!

> > a) how to boot linux (can I just branch to the the address where I loaded t
> > he
> > image into ram or do I need to setup registers / data structures beforehand?)
>
> Yes, you need to setup a number of things.  Take a look at PPCBoot (now called
> U-Boot).  Porting PPCBoot is pretty straight forward.  Once you have
> PPCBoot support done for the board, you're pretty far along.

I've got a VxWorks boot loader on the thing, so I'm not worrying about a
boot loader right now. I just need to know what I need to setup before
branching to the processor. Looking at the source for the 8xx processors, it
seems I need:

------------< snip <------< snip <------< snip <------------
r3: ptr to board info data
r4: initrd_start or if no initrd then 0
r5: initrd_end - unused if r4 is 0
r6: start of command line string
r7: end of command line string
------------< snip <------< snip <------< snip <------------

Is that all? Also, what is the "board info data" ?

> > b) where/what do I change if I want to add a "sub" architecture?
>
> arch/ppc/platforms is what you want.  You need a LinuxPPC tree with
> what they call "platforms" support.  You can get one from the BK
> repositories.

I downloaded ppc-patch-2.4.18.bz2 from
ftp://ftp.kernel.org/pub/linux/kernel/ports/ppc - is that sufficient or is
there better support in the BK repository?

> > I've got a ICP-PPC PowerPC backplane type system here which I want to get
> > Linux on. It has the MPC8240 CPU on it which from what I read is pretty much
> > the same as the 8260, 8245, etc. (they're all based on the 603e core right?)
> >
> > Now, if I select "8xx" in menuconfig, I get another selection of machine
> > types (RPX-Lite, RPX-Classic, etc.). Obviously I need to own my own machine
> > type here, but how do I do that. Also, how does these machine types differ?
> > Just different peripherals? Do they have anything in common (e.g. uart).
>
> For the most part, anything based on the 8240 is going to be roughly
> similar.  You'll have to know how the chip selects are configured, and
> possibly the SDRAM controller setup, but that's usually handled by PPCBoot.
> Sometimes the kernel does additional setup in arch/ppc/platforms for
> specific targets (eg. PCI bridge config, etc.) you'll see what I mean.

Well, the boot loader have everything configured already. I'm not worried
about peripherals for now, just booting the kernel.

--

Regards
 Abraham

The first thing I do in the morning is brush my teeth and sharpen my tongue.
		-- Dorothy Parker

__________________________________________________________
 Abraham vd Merwe - 2d3D, Inc.

 Device Driver Development, Outsourcing, Embedded Systems

  Cell: +27 82 565 4451         Snailmail:
   Tel: +27 21 761 7549            Block C, Aintree Park
   Fax: +27 21 761 7648            Doncaster Road
 Email: abraham@2d3d.co.za         Kenilworth, 7700
  Http: http://www.2d3d.com        South Africa

** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/

Re: looking for documentation on porting Linux to PowerPC platforms

[Chris Zimman]

On Thu, Dec 05, 2002 at 10:48:56AM +0200, Abraham vd Merwe wrote:
> I've got a VxWorks boot loader on the thing, so I'm not worrying about a
> boot loader right now. I just need to know what I need to setup before
> branching to the processor. Looking at the source for the 8xx processors, it
> seems I need:

I've never looked at the VxWorks boot loader, so I'm not sure how it
does things.

> ------------< snip <------< snip <------< snip <------------
> r3: ptr to board info data
> r4: initrd_start or if no initrd then 0
> r5: initrd_end - unused if r4 is 0
> r6: start of command line string
> r7: end of command line string
> ------------< snip <------< snip <------< snip <------------
>
> Is that all? Also, what is the "board info data" ?

bd_t contains parameters for the kernel (eg. start of memory, size,
start of flash, etc.).

> I downloaded ppc-patch-2.4.18.bz2 from
> ftp://ftp.kernel.org/pub/linux/kernel/ports/ppc - is that sufficient or is
> there better support in the BK repository?

You'd probably be best getting the code from the BK repository.  Again,
what you most likely want is 2.4.x + platforms.

--Chris

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Re: looking for documentation on porting Linux to PowerPC platforms

[Abraham vd Merwe]

Hi Benjamin!

> > Is there a document somewhere describing the basics about the PowerPC
> > platform and Linux, i.e.
>
> Not really afaik, I should probably do this though ;)

It would be really useful to have something like that.

> > a) how to boot linux (can I just branch to the the address where I loaded t
> > he
> > image into ram or do I need to setup registers / data structures beforehand?)
>
> Custom hardware ? Well, that pretty much depends how your implementation
> of early init & setup_arch behaves. The kernel itself can be loaded at
> almost any address on most ppc32 CPUs, it will relocate itself, though
> you probably want to make sure you enter it with MMU translations
> disabled.

What about caches? Do you care whether caching is enabled or not?

--

Regards
 Abraham

The giraffe you thought you offended last week is willing to be nuzzled today.

__________________________________________________________
 Abraham vd Merwe - 2d3D, Inc.

 Device Driver Development, Outsourcing, Embedded Systems

  Cell: +27 82 565 4451         Snailmail:
   Tel: +27 21 761 7549            Block C, Aintree Park
   Fax: +27 21 761 7648            Doncaster Road
 Email: abraham@2d3d.co.za         Kenilworth, 7700
  Http: http://www.2d3d.com        South Africa

** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/

Re: looking for documentation on porting Linux to PowerPC platforms

[Benjamin Herrenschmidt]

> What about caches? Do you care whether caching is enabled or not?

Not really. We do enable L1 on "common" desktop CPUs, and machine
specific code may do more with L2 or L3 if any. It's up to you to
either setup additional caches prior to entering the kernel, or from
your machine init code.

Ben.


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