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    SubjectRe: [PATCH 0/3] GIC OF bindings
    On 9/20/2011 6:14 PM, Grant Likely wrote:
    > On Tue, Sep 20, 2011 at 8:49 PM, David Miller<davem@davemloft.net> wrote:
    >> From: Rob Herring<robherring2@gmail.com>
    >> Date: Tue, 20 Sep 2011 15:24:01 -0500
    >>
    >>> Hopefully, this is the final or near final version of GIC binding support.
    >>>
    >>> Changes from the previous version:
    >>> - SPIs and PPIs are numbered starting at 0. Now the gic has it's own irq
    >>> domain translate function instead of the simple domain one.
    >>> - interrupt cell format has changed based on Grant's proposal.
    >>> - Dropped "ARM: gic: allow irq_start to be 0". Instead, the first 16 irqs
    >>> are skipped and the domain irq_base adjusted accordingly.
    >>> - Added a fix to of_irq_find_parent when the parent == child.
    >>> - Renamed intc_desc.parent to intc_desc.interrupt_parent.
    >>> - Implemented Grant's algorithm for walking the list of interrupt
    >>> controllers. Added a return value to interrupt init functions, so they
    >>> don't get added to the parent list on a init failure.
    >>>
    >>> The changes are significant enough that I did not include previous
    >>> acked/reviewed/tested-by's.
    >>
    >> Just out of curiosity where does this "interrupt-parent" property
    >> come from?
    >>
    >> On platforms I am familiar with, the parent path is walked to the root
    >> and we stop at device nodes that have "interrupt-map" and
    >> "interrupt-map-mask" properties.
    >>
    >> The map and mask are applied to the "reg" property of the device in
    >> question to see which map entry matches, if a match is found the map
    >> entry contains the translated interrupt.
    >>
    >> And this process continues over and over all the way to the root to get
    >> the system interrupt that processor actually deals with.
    >>
    >> The mechanism shown here seems overly simplistic and not able to handle
    >> the cases handled by existing OF property schemes in use for several
    >> years on real systems.
    >
    > interrupt-parent has been implemented for years on powerpc. I don't
    > know if it was ever an Open Firmware thing, but it is in ePAPR [1],
    > and ARM isn't doing anything novel in that regard.

    interrupt-parent has been part of the interrupt mapping spec from the
    inception of same.

    http://www.openfirmware.info/docs/rec.intmap.d09.pdf

    >
    > [1] section 2.4, page 30,
    > https://www.power.org/resources/downloads/Power_ePAPR_APPROVED_v1.1.pdf
    >
    > It is true that is cannot handle all situations, but for those
    > interrupt-map is still available.
    >
    > g.
    > _______________________________________________
    > devicetree-discuss mailing list
    > devicetree-discuss@lists.ozlabs.org
    > https://lists.ozlabs.org/listinfo/devicetree-discuss
    >
    >


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