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 <marc.zyng...@arm.com> >> 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. > 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. > }; > > 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. Rob > M. _______________________________________________ devicetree-discuss mailing list devicetree-discuss@lists.ozlabs.org https://lists.ozlabs.org/listinfo/devicetree-discuss