Device Tree setup for 8272-based board

[Scott Wood]

On Fri, Jan 16, 2009 at 02:40:03PM +1100, Daniel Ng wrote:
> I've tried various values for 'console' but I'm quite certain 'ttyCPM0' is the
> one to use as this is what I was using when it was working with Linux 2.6.14
> and an old (pre-Device Tree) version of u-boot.

Yes, that is correct.  You can also leave it out and rely on
/chosen/linux,stdout-path.

> I've even tried enabling the 'Early serial debugging for Freescale CPM-based
> serial ports' option in the Kernel config. Unfortunately this doesn't result
> in any noticeable difference.
> 
> Can you explain why my board is freezing?
> 
> Here is my Device Tree. It is a stripped-down version of mpc8272ads.dts (PCI
> has been removed among many others). I have tried to minimise the tree just to
> keep things simple.
> 
> Perhaps I removed something I shouldn't have?-

You removed the brg node, but early debug output should still work
without it.

> /dts-v1/;
> 
> / {
> model = "HPXRED";
> compatible = "fsl,mpc8272ads";

Is it 100% compatible?  If not, change the compatible to something else
(and make sure your board code matches it).

Do you currently have mpc8272ads support enabled in the kernel?  If the
kernel doesn't find a matching ppc_md, you won't get any debug output. 

You can use udbg_printf() directly after the call to udbg_early_init()
though.

-Scott