device tree in open firmware on power6

Paul Mackerras paulus at
Thu May 8 16:32:50 EST 2008

Chandru writes:

> When I set linux 2.6.26-rc1 as default kernel to boot in 
> /etc/yaboot.conf, then the device tree in open firmware shows only one 
> memory node ( the same memory node appears in /proc/device-tree/memory at 0 
> ).  But when RHEL5.2 kernel is set as default in /etc/yaboot.conf then 
> the device tree in open firmware shows plenty of memory nodes. Following 
> is the open firmware output..

Current kernels tell the firmware that they can handle having memory
represented in the /ibm,dynamic-reconfiguration-memory node, which is
a more compact representation than having it represented in multiple
/memory at xxx nodes.  Therefore firmware reports most of the memory in
the /ibm,dynamic-reconfiguration-memory node you have here:

> linux-2.6.26-rc1:
> <snip>
> 0 > dev / ls
> ...
> 000000caf1b8:   /PowerPC,POWER6 at 6
> 000000cb0120: /memory at 0
> 000000cb83d8: /ibm,dynamic-reconfiguration-memory

and only gives you one /memory at xxx node, which represents the real
memory area.  See sections C.6.2.3 and C.6.6.2 of PAPR for more


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