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    SubjectRe: [PATCH 4/4] arm64: dts: uniphier: Add NX1 SoC and boards support
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    On 2022/10/27 20:28, Arnd Bergmann wrote:
    > On Thu, Oct 27, 2022, at 13:19, Kunihiko Hayashi wrote:
    >> On 2022/10/27 19:01, Arnd Bergmann wrote:
    >>> On Thu, Oct 27, 2022, at 06:51, Kunihiko Hayashi wrote:
    >
    >>>> + #interrupt-cells = <1>;
    >>>> + interrupt-names = "dma", "msi";
    >>>> + interrupts = <GIC_SPI 84 IRQ_TYPE_LEVEL_HIGH>,
    >>>> + <GIC_SPI 85 IRQ_TYPE_LEVEL_HIGH>;
    >>>> + interrupt-map-mask = <0 0 0 7>;
    >>>> + interrupt-map = <0 0 0 1 &pcie_intc 0>, /* INTA */
    >>>> + <0 0 0 2 &pcie_intc 1>, /* INTB */
    >>>> + <0 0 0 3 &pcie_intc 2>, /* INTC */
    >>>> + <0 0 0 4 &pcie_intc 3>; /* INTD */
    >>>> + phy-names = "pcie-phy";
    >>>> + phys = <&pcie_phy>;
    >>>> +
    >>>> + pcie_intc: legacy-interrupt-controller {
    >>>> + interrupt-controller;
    >>>> + #interrupt-cells = <1>;
    >>>> + interrupt-parent = <&gic>;
    >>>> + interrupts = <GIC_SPI 86
    >>> IRQ_TYPE_LEVEL_HIGH>;
    >>>> + };
    >>>> + };
    >>>
    >>> Shouldn't there be an "msi-map" or "msi-parent" property pointing at
    >>> the GIC?
    >>
    >> Since Designware PCIe receives an interrupt from GIC with interrupt-name
    > "msi"
    >> and passes the interrupt to the linear irq domain corresponding to MSI,
    >> I think there is neither "msi-map" nor "msi-parent" properties.
    >
    > Usually, you have the choice to use either the built-in
    > MSI logic of the PCIe controller, or the one built into the
    > GIC itself, assuming you have a modern enough GIC implemetation.

    I recognize ITS built into GICv3 can perform the parent of MSI.

    > Using the GIC is preferred here, because otherwise you lose
    > all the benefits that MSIs offer, regarding latency and CPU
    > affinity.

    I understand, however, unfortunately GIC-ITS (or something alternative)
    isn't supported in this SoC, so I think it is difficult to use the GIC
    itself as msi-parent.

    Thank you,

    ---
    Best Regards
    Kunihiko Hayashi

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