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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2013-11-22 at 14:50 +0000, Julien Grall wrote:
> 
> 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).
> >>>
> >>> Therefore:
> >>>    - 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.

OK, so my point was that this is a bit of a non-issue, at least right
now. And running on such a system is going to take actual work beyond
some platform quirks etc.

> 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.

Right. I'll do this.

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

OK.
> 



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