linux-kernel - Re: [PATCH v2 3/3] arm64: dts: qcom: sm8450: Use GIC-ITS for PCIe0 and PCIe1

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Date:   Fri, 23 Dec 2022 19:18:32 +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 v2 3/3] arm64: dts: qcom: sm8450: Use GIC-ITS for PCIe0
 and PCIe1

On 22/12/2022 15:31, 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.
> 
> It should be noted that the MSIs for BDF (1:0.0) only works with Device
> ID of 0x5980 and 0x5a00. Hence, the IDs are swapped.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>   arch/arm64/boot/dts/qcom/sm8450.dtsi | 20 ++++++++++++++------
>   1 file changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sm8450.dtsi b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> index 570475040d95..c4dd5838fac6 100644
> --- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> @@ -1733,9 +1733,13 @@ 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>;
> +			/*
> +			 * MSIs for BDF (1:0.0) only works with Device ID 0x5980.
> +			 * Hence, the IDs are swapped.
> +			 */
> +			msi-map = <0x0 &gic_its 0x5981 0x1>,
> +				  <0x100 &gic_its 0x5980 0x1>;

This definitely doesn't match what has been used in the downstream.

Also if I understand correctly this change would prevent us from using 
multiple MSI interrupts for the connected device, as the last value of 
the 0x100 mapping is 0x1, while the vendor kernel uses <0x100 &its 
0x5981 0x20>.

Do you know by chance, why do we differ from the vendor dtsi?

> +			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 +1846,13 @@ 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>;
> +			/*
> +			 * MSIs for BDF (1:0.0) only works with Device ID 0x5a00.
> +			 * Hence, the IDs are swapped.
> +			 */
> +			msi-map = <0x0 &gic_its 0x5a01 0x1>,
> +				  <0x100 &gic_its 0x5a00 0x1>;
> +			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