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From:   Jassi Brar <jassisinghbrar@gmail.com>
Date:   Thu, 28 Jul 2022 16:07:45 -0500
Message-ID: <CABb+yY0JzztBB+giBu+RCt-dzgwYWF32sCR3WKKP9U5K9UvhxA@mail.gmail.com>
Subject: Re: [PATCH] dt-bindings: mailbox: arm,mhu: Make secure interrupt optional
To:     Rob Herring <robh@kernel.org>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Jassi Brar <jaswinder.singh@linaro.org>,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
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On Thu, Jul 28, 2022 at 3:17 PM Jassi Brar <jassisinghbrar@gmail.com> wrote:
>
> On Thu, Jul 28, 2022 at 2:08 PM Rob Herring <robh@kernel.org> wrote:
> >
> > The secure interrupt is only useful to secure world, therefore for NS
> > users it shouldn't be required. Make it optional.
> >
> > This fixes a warning on Arm Juno board:
> >
> > mhu@2b1f0000: interrupts: [[0, 36, 4], [0, 35, 4]] is too short
> >
> > Signed-off-by: Rob Herring <robh@kernel.org>
> > ---
> >  Documentation/devicetree/bindings/mailbox/arm,mhu.yaml | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/Documentation/devicetree/bindings/mailbox/arm,mhu.yaml b/Documentation/devicetree/bindings/mailbox/arm,mhu.yaml
> > index bd49c201477d..d9a4f4a02d7c 100644
> > --- a/Documentation/devicetree/bindings/mailbox/arm,mhu.yaml
> > +++ b/Documentation/devicetree/bindings/mailbox/arm,mhu.yaml
> > @@ -57,6 +57,7 @@ properties:
> >      maxItems: 1
> >
> >    interrupts:
> > +    minItems: 2
> >      items:
> >        - description: low-priority non-secure
> >        - description: high-priority non-secure
> >
> Do we also want to specify that only the secure-irq is optional
> because irqs are directly mapped onto channels in the driver, and only
> omitting the secure (last) irq will work.
>
I could learn why specifying secure irq isn't desirable?
No non-secure client node would ask for that secure irq/channel, which
will simply lay unused.

The programming of the secure channel doesn't care if the mode is
indeed secure. It all relies on providing accurate information in the
device tree :- the controller provides secure and non-secure channels
but only non-secure channels are _used_ in non-secure mode.

diff --git a/arch/arm64/boot/dts/arm/juno-base.dtsi
b/arch/arm64/boot/dts/arm/juno-base.dtsi
index f6c55877fbd94..004b1566be74d 100644
--- a/arch/arm64/boot/dts/arm/juno-base.dtsi
+++ b/arch/arm64/boot/dts/arm/juno-base.dtsi
@@ -26,7 +26,8 @@ mailbox: mhu@2b1f0000 {
        compatible = "arm,mhu", "arm,primecell";
        reg = <0x0 0x2b1f0000 0x0 0x1000>;
        interrupts = <GIC_SPI 36 IRQ_TYPE_LEVEL_HIGH>,
-                <GIC_SPI 35 IRQ_TYPE_LEVEL_HIGH>;
+                <GIC_SPI 35 IRQ_TYPE_LEVEL_HIGH>,
+                <GIC_SPI 37 IRQ_TYPE_LEVEL_HIGH>;
        interrupt-names = "mhu_lpri_rx",
                  "mhu_hpri_rx";
        #mbox-cells = <1>;

If this works for you, I could submit a proper patch.

thanks.