linux-kernel - Re: [PATCH v3 5/5] arm64: dts: qcom: sa8775p: Add ep pcie0 controller node

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Date:   Wed, 25 Oct 2023 13:22:24 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Mrinmay Sarkar <quic_msarkar@...cinc.com>
Cc:     agross@...nel.org, andersson@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        konrad.dybcio@...aro.org, quic_shazhuss@...cinc.com,
        quic_nitegupt@...cinc.com, quic_ramkri@...cinc.com,
        quic_nayiluri@...cinc.com, dmitry.baryshkov@...aro.org,
        robh@...nel.org, quic_krichai@...cinc.com,
        quic_vbadigan@...cinc.com, quic_parass@...cinc.com,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Vinod Koul <vkoul@...nel.org>, linux-pci@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, mhi@...ts.linux.dev,
        linux-phy@...ts.infradead.org
Subject: Re: [PATCH v3 5/5] arm64: dts: qcom: sa8775p: Add ep pcie0
 controller node

On Thu, Oct 19, 2023 at 05:07:10PM +0530, Mrinmay Sarkar wrote:
> Add ep pcie dtsi node for pcie0 controller found on sa8775p platform.
> It supports gen4 and x2 link width. Due to some stability issue in
> gen4 enabling gen3 as of now.
> 
> Signed-off-by: Mrinmay Sarkar <quic_msarkar@...cinc.com>
> ---
>  arch/arm64/boot/dts/qcom/sa8775p.dtsi | 48 +++++++++++++++++++++++++++++++++++
>  1 file changed, 48 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sa8775p.dtsi b/arch/arm64/boot/dts/qcom/sa8775p.dtsi
> index 13dd44d..2aa7383 100644
> --- a/arch/arm64/boot/dts/qcom/sa8775p.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sa8775p.dtsi
> @@ -3714,4 +3714,52 @@
>  
>  		status = "disabled";
>  	};
> +
> +	pcie0_ep: pcie-ep@...0000 {
> +		compatible = "qcom,sa8775p-pcie-ep";
> +		reg = <0x0 0x01c00000 0x0 0x3000>,
> +		      <0x0 0x40000000 0x0 0xf20>,
> +		      <0x0 0x40000f20 0x0 0xa8>,
> +		      <0x0 0x40001000 0x0 0x4000>,
> +		      <0x0 0x40200000 0x0 0x100000>,
> +		      <0x0 0x01c03000 0x0 0x1000>,
> +		      <0x0 0x40005000 0x0 0x2000>;

Can we sort the reg entries?

> +		reg-names = "parf", "dbi", "elbi", "atu", "addr_space",
> +			    "mmio", "dma";
> +
> +		clocks = <&gcc GCC_PCIE_0_AUX_CLK>,
> +			<&gcc GCC_PCIE_0_CFG_AHB_CLK>,
> +			<&gcc GCC_PCIE_0_MSTR_AXI_CLK>,
> +			<&gcc GCC_PCIE_0_SLV_AXI_CLK>,
> +			<&gcc GCC_PCIE_0_SLV_Q2A_AXI_CLK>;
> +
> +		clock-names = "aux",
> +			      "cfg",
> +			      "bus_master",
> +			      "bus_slave",
> +			      "slave_q2a";
> +
> +		interrupts = <GIC_SPI 306 IRQ_TYPE_LEVEL_HIGH>,
> +			     <GIC_SPI 147 IRQ_TYPE_LEVEL_HIGH>,
> +			     <GIC_SPI 630 IRQ_TYPE_LEVEL_HIGH>;
> +
> +		interrupt-names = "global", "doorbell", "dma";
> +
> +		interconnects = <&pcie_anoc MASTER_PCIE_0 0 &mc_virt SLAVE_EBI1 0>,
> +				<&gem_noc MASTER_APPSS_PROC 0 &config_noc SLAVE_PCIE_0 0>;
> +		interconnect-names = "pcie-mem", "cpu-pcie";
> +
> +		iommu-map = <0x0 &pcie_smmu 0x0000 0x1>,
> +			    <0x100 &pcie_smmu 0x0001 0x1>;

I think I recommended using "iommu-map" instead of "iommus" property. But
looking at it again, I think it is fine to use just "iommus" property as the SID
will be associated with the EP directly.

Unless you want to have different SID for each function.

> +
> +		resets = <&gcc GCC_PCIE_0_BCR>;
> +		reset-names = "core";
> +		power-domains = <&gcc PCIE_0_GDSC>;
> +		phys = <&pcie0_phy>;
> +		phy-names = "pciephy";
> +		max-link-speed = <3>;

Please add a comment here that you are limiting the Gen speed due to stability
issues. Like,

		max-link-speed = <3>; /* FIXME: Limiting the Gen speed due to stability issues */

> +		num-lanes = <2>;

Can you check if the controller is cache coherent? If so, we should add
"dma-coherent" property.

- Mani

> +
> +		status = "disabled";
> +	};
>  };
> -- 
> 2.7.4
> 

-- 
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