linux-kernel - Re: [PATCH 3/3] arm64: dts: qcom: sm8450: Use GIC-ITS for PCIe0 and PCIe1

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Date:   Mon, 19 Dec 2022 23:46:03 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        andersson@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org
Cc:     bhelgaas@...gle.com, konrad.dybcio@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] arm64: dts: qcom: sm8450: Use GIC-ITS for PCIe0 and
 PCIe1

On 19/12/2022 21:14, Manivannan Sadhasivam wrote:
> Both PCIe0 and PCIe1 controllers are capable of receiving MSIs from
> endpoint devices using GIC-ITS MSI controller. Add support for it.
> 
> Currently, BDF (0:0.0) and BDF (1:0.0) are enabled and with the
> msi-map-mask of 0xff00, all the 32 devices under these two busses can
> share the same Device ID.
> 
> The GIC-ITS MSI implementation provides an advantage over internal MSI
> implementation using Locality-specific Peripheral Interrupts (LPI) that
> would allow MSIs to be targeted for each CPU core.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>   arch/arm64/boot/dts/qcom/sm8450.dtsi | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sm8450.dtsi b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> index 570475040d95..276ceba4c247 100644
> --- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> @@ -1733,9 +1733,9 @@ pcie0: pci@...0000 {
>   			ranges = <0x01000000 0x0 0x60200000 0 0x60200000 0x0 0x100000>,
>   				 <0x02000000 0x0 0x60300000 0 0x60300000 0x0 0x3d00000>;
>   
> -			interrupts = <GIC_SPI 141 IRQ_TYPE_LEVEL_HIGH>;
> -			interrupt-names = "msi";
> -			#interrupt-cells = <1>;
> +			msi-map = <0x0 &gic_its 0x5980 0x1>,
> +				  <0x100 &gic_its 0x5981 0x1>;

Does ITS support handling more than one MSI interrupt per device? 
Otherwise it might be better to switch to multi-MSI scheme using SPI 
interrupts.

> +			msi-map-mask = <0xff00>;
>   			interrupt-map-mask = <0 0 0 0x7>;
>   			interrupt-map = <0 0 0 1 &intc 0 0 0 149 IRQ_TYPE_LEVEL_HIGH>, /* int_a */
>   					<0 0 0 2 &intc 0 0 0 150 IRQ_TYPE_LEVEL_HIGH>, /* int_b */
> @@ -1842,9 +1842,9 @@ pcie1: pci@...8000 {
>   			ranges = <0x01000000 0x0 0x40200000 0 0x40200000 0x0 0x100000>,
>   				 <0x02000000 0x0 0x40300000 0 0x40300000 0x0 0x1fd00000>;
>   
> -			interrupts = <GIC_SPI 307 IRQ_TYPE_LEVEL_HIGH>;
> -			interrupt-names = "msi";
> -			#interrupt-cells = <1>;
> +			msi-map = <0x0 &gic_its 0x5a01 0x1>,
> +				  <0x100 &gic_its 0x5a00 0x1>;

Are you sure that the order is correct here?

> +			msi-map-mask = <0xff00>;
>   			interrupt-map-mask = <0 0 0 0x7>;
>   			interrupt-map = <0 0 0 1 &intc 0 0 0 434 IRQ_TYPE_LEVEL_HIGH>, /* int_a */
>   					<0 0 0 2 &intc 0 0 0 435 IRQ_TYPE_LEVEL_HIGH>, /* int_b */

-- 
With best wishes
Dmitry