On 05/04/12 14:34, Rob Herring wrote:
> On 04/05/2012 07:59 AM, Marc Zyngier wrote:
>> On 03/04/12 16:35, Grant Likely wrote:
>>
>> Hi Grant,
>>
>>> On Tue, 03 Apr 2012 10:53:44 +0100, Marc Zyngier <[email protected]>
>>> wrote:
>>>> On 03/04/12 10:22, David Vrabel wrote:
>>>>
>>>> Hi David,
>>>>
>>>>> On 02/04/12 17:30, Marc Zyngier wrote:
>>>>>> The GICv2 can have virtualization extension support, consisting
>>>>>> of an additional set of registers and interrupts. Add the necessary
>>>>>> binding to the GIC DT documentation.
>>>>>
>>>>> The Xen hypervisor's device tree support is very much incomplete so I've
>>>>> not looked into this is much detail.
>>>>>
>>>>> Would it make more sense to extend the existing gic binding with the the
>>>>> additional information rather than adding a new node?
>>>>
>>>> I'm actually torn between the two approaches. On one side, the VGIC is
>>>> part of the GIC spec, hence should be part of the GIC node. On the other
>>>> hand, it is logically handled by a different piece of software (the
>>>> hypervisor), and would normally be probed separately. Having a separate
>>>> node makes the probing more sensible.
>>>
>>> Don't get too hung up on the software side of things. Describe it in
>>> a way that makes sense for the hardware. There is lots of precidence
>>> for two hunks of software initializating from the same node; either by
>>> probe kicking off two init hooks, or by early init code going looking
>>> for the node manually.
>>
>> What I'm trying to avoid is a royal mess in the future if we get some
>> other extension to the GIC.
>>
>
> But that would be a new compatible string as is this case.
Yes, probably.
>> Let's say we implement the following:
>>
>> gic: interrupt-controller@2c001000 {
>> compatible = "arm,cortex-a15-gic";
>> #interrupt-cells = <3>;
>> #address-cells = <1>;
>> interrupt-controller;
>> reg = <0x2c001000 0x1000>,
>> <0x2c002000 0x100>,
>> <0x2c004000 0x2000>,
>> <0x2c006000 0x2000>;
>> interrupts = <1 9 0xf04>;
>
> Does this work having an interrupt within the parent itself? Normally
> this would be the connection to the next level up.
In this case we don't have an interrupt parent property, so the GIC is
properly identified as the top-level interrupt controller. This is
admittedly a bit fragile, and contradicts the current wording of the
binding.
>> };
>>
>> It's all fine (the two last regions and the interrupt are for VGIC),
>> until someone comes up with extension FOO which requires two new regions
>> and am interrupt. It is then impossible to distinguish between the two,
>> short of adding more attributes.
>>
>> How about this?
>>
>> gic: interrupt-controller@2c001000 {
>> compatible = "arm,cortex-a15-gic";
>> #interrupt-cells = <3>;
>> #address-cells = <1>;
>> #size-cells = <1>;
>> interrupt-controller;
>> reg = <0x2c001000 0x1000>,
>> <0x2c002000 0x100>;
>>
>> vgic@2c004000 {
>> compatible = "arm,cortex-a15-vgic", "arm,vgic";
>> reg = <0x2c004000 0x2000>,
>> <0x2c006000 0x2000>;
>> interrupts = <1 9 0xf04>;
>> };
>> };
>>
>> It cleanly separate the extension from the core GIC, and still make it
>> part of the GIC node.
>>
>> What do you think?
>>
>
> I prefer the first option.
The first I posted (vgic node outside of the gic), or the one with
everything in the same node?
M.
--
Jazz is not dead. It just smells funny...
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