Re: [PATCH] Add MPC8641 HPCN Device Tree Source file.

On Wed, Aug 02, 2006 at 02:50:17PM -0500, Hollis Blanchard wrote:

On Wed, 2006-08-02 at 13:48 -0500, Jon Loeliger wrote:

quoted

+               PowerPC,8641@0 {
+                       device_type = "cpu";
+                       reg = <0>;
+                       d-cache-line-size = <20>;       // 32 bytes
+                       i-cache-line-size = <20>;       // 32 bytes
+                       d-cache-size = <8000>;          // L1, 32K
+                       i-cache-size = <8000>;          // L1, 32K
+                       timebase-frequency = <0>;       // 33 MHz,
from uboot
+                       bus-frequency = <0>;            // From uboot
+                       clock-frequency = <0>;          // From uboot
+                       32-bit;
+                       linux,boot-cpu;
+               }; 

I need to do something similar for Xen, so I was curious: I guess the
preferred way for runtime software to fill in values is by *overwriting*
bogus values inserted at compile time?

The other alternative would be for the runtime code to insert new
properties (presumably via memmove()), but overwriting definitely seems
simpler.

Two reasons you may want to overwrite instead of insert a new one (at
least for now):

1) Strictly opinion: Its nice to be able to see the completely
functional tree and not one that's missing a critical property
that is magically inserted behind the scenes.

2) Strictly practical for now: If you plan on using a zImage with
the fdt patches that are being discussed right now, the fdt code
doesn't currently support inserting a new property, only modifying an
existing one.  Patches always welcome though! :)

Mark