On Wed, Oct 14, 2015 at 5:18 AM, Qais Yousef <qais.yousef@xxxxxxxxxx> wrote: > Hi, > > This is an attempt to revive a discussion on the right list this time with > all the correct people hopefully on CC. devicetree-spec would be more appropriate list for something like this. > While trying to upstream a driver, Thomas and Marc Zyngier pointed out the > need for a generic IPI support in the kernel to allow driver to reserve and > send ones. Hopefully my latest RFC patch will help to clarify what's being > done. > > https://lkml.org/lkml/2015/10/13/227 > > We need a generic DT binding support to accompany that to allow a driver to > reserve an IPI using this new mechanism. > > MarcZ had the following suggestion: > > https://lkml.org/lkml/2015/8/24/628 > > Which in summary is > > mydevice@f0000000 { > interrupt-source = <&intc INT_SPEC 2 &inttarg1 &inttarg1>; What is INT_SPEC and "2"? A drawing of the h/w connections and then what the binding looks like would be helpful. > }; > > inttarg1: mydevice@f1000000 { > interrupt-sink = <&intc HWAFFINITY1>; What is HWAFFINITY1? I want to be able to see if say this value is 1, then the affinity is for cpu0. > }; > > inttarg2: cpu@1 { > interrupt-sink = <&intc HWAFFINITY2>; > }; > > > interrupt-sink requests to reserve an IPI that it will receive at HWAFFINITY > cpumask. interrupt-source will not do any reservation. It will simply > connect an IPI reserved by interrupt-sink to the device that will be > responsible for generating that IPI. This description should allow > connecting any 2 devices. > Correct me Marc if I got it wrong please. > > I suggested a simplification by assuming that IPIs will only be between host > OS and a coprocessor which would gives us this form which I think is easier > to deal with > > coprocessor { > interrupt-source = <&intc INT_SPEC COP_HWAFFINITY>; > interrupt-sink = <&intc INT_SPEC CPU_HWAFFINITY>; > } > > > interrupt-source here reserves an IPI to be sent from host OS to coprocessor > at COP_HWAFFINITY. interrupt-sink will reserve an IPI to be received by host > OS at CPU_HWAFFINITY. Less generic but I don't know how important it is for > host OS to setup IPIs between 2 external coprocessors and whether it should > really be doing that. Could we use the existing interrupts binding for interrupt-sink? > > What do the DT experts think? Any preference or a better suggestion? Depends how you would assign coproc to coproc IPIs in a system. It may be fixed in firmware, or more complex coprocs may read the dtb. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
