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Re: [Xen-devel] [PATCH] xen: arm: remove /xen-core-devices node from dom0 dtb

On 11/22/2013 02:40 PM, Ian Campbell wrote:
On Fri, 2013-11-22 at 14:18 +0000, Julien Grall wrote:

On 11/22/2013 01:47 PM, Ian Campbell wrote:
The intention of adding this node to contain the GIC, timer and memory nodes
(in 1c08d6004ea7) was to allow us to control the #address-cells and

However in the case of the memory node the #*-cells are always taken from the
root node (see ePAPR 3.1, "the following nodes shall be present at the root...
memory node"). This caused breakage on the arndale platform.

In addition it is not valid to just create sub-nodes like this. Unless they
declare themselves as a bus then they will not necessarily be enumerated
(although Linux currently does so in practice).

   - Move the memory node back to the top level.
   - Insert the timer and gic nodes in the same location as in the host DTB,
     replacing the originals. Note that the nodes here may be marked as in use
     by Xen and therefore the check must be before we discard nodes used by Xen.

If you insert the GIC and timer nodes at the same location you need to
make sure the use the right value. For instance it may happen to have
multiple GIC in the device tree.
Actually, Xen skips all the GIC nodes and create just one. Here, you
replace all the possible GIC nodes by the same value (I'm not sure how
Linux will deal with that).

Damn, I forgot about this case. I'm not sure how relevant it is to us
today though -- do we support any such systems and/or would they be
likely to just work, I would expect not?

We don't support this kind of systems. Xen only handle one GIC at time in arch/arm/gic.c. During dom0 DT building we will just remove all GIC nodes and just create one (the main controller).

For now, I think the best the solution is to check if we are the main
interrupt controller. If not, the function just need to return 0.

Means checking dt_interrupt_controller->phandle against the node in
hand, right?

You give in argument the current node pointer (ie the GIC). So you can compare this pointer to dt_interrupt_controller.

BTW, the name of the argument "parent" is wrong. It's not the parent but the current node. I would rename to "np".

Julien Grall

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