Linux-2.1.129 boot on MCP750 <fwd>

[Gabriel Paubert]

On Wed, 9 Dec 1998, Alois Fertl wrote:

> 
> Yes its possible to change the locations where ppcbug loads via the net
> via the "niot" command. To my experience this address is only used if
> the "network prep mode" is switched off. If you switch this off the
> ppcbug
> does no longer prepare residual data (use "nbh" and you will see that R3
> is zero). No residual data means that the raven is not detected and the
> code uses direct access to scan for PCI devices. As this will not work
> on the raven and you end up with no PCI at all.

A solution would be to add code to check if the value returned from
reading at 0x80800008 returns something like a host bridge (0x0600????
little endian). 

Oe maybe the other way around: fall back to direct config method if
after writing 0x80000008 at 0x80000cf8, 0x80000cfc does not show to be a
host bridge.

The preceding assumes that host bridge is device 0 on the PCI bus (it
usually is). But in any case I prefer to rely on residual data if
available: residual data is necessary to use the OpenPIC which is inside
the Raven. 

> I do not know however which kernel version introduced this method of
> detecting the raven via the residual data. If I remember correctly it
> was possible to boot at least 2.0.32 with network prep mode switched
> off.

Note that this was because of netboot problems onn the MVME2600 that I
started wrting my bootloader. It self relocates according to the free
areas as given by the residual data and is compiled with -m relocatable
option to make it 100% position independant. But it has other problems
since it seems to only work on MVME2603 (nor even 2604). I would like to
put my hands on some other HW because trying to debug this low level code
through the net is not fun. 

	Gabriel.


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