linux-kernel - Re: [PATCH v5 3/3] PCI: qcom-ep: Add ICC bandwidth voting support

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Message-ID: <bdce0719-4f12-4e75-a8e7-1b38d269ac15@quicinc.com>
Date:   Tue, 27 Jun 2023 12:05:23 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Krishna chaitanya chundru <quic_krichai@...cinc.com>
CC:     <manivannan.sadhasivam@...aro.org>, <helgaas@...nel.org>,
        <linux-pci@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_vbadigan@...cinc.com>,
        <quic_nitegupt@...cinc.com>, <quic_skananth@...cinc.com>,
        <quic_ramkri@...cinc.com>, <krzysztof.kozlowski@...aro.org>,
        "Manivannan Sadhasivam" <mani@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v5 3/3] PCI: qcom-ep: Add ICC bandwidth voting support

On Tue, Jun 27, 2023 at 06:31:31AM +0530, Krishna chaitanya chundru wrote:
> +static void qcom_pcie_ep_icc_update(struct qcom_pcie_ep *pcie_ep)
> +{
> +	struct dw_pcie *pci = &pcie_ep->pci;
> +	u32 offset, status, bw;
> +	int speed, width;
> +	int ret;
> +
> +	if (!pcie_ep->icc_mem)
> +		return;
> +

Is this check needed? interconnect is added as required property and
probe is failed if interconnect get fails. qcom_pcie_enable_resources()
which gets called before enabling this interrupt is assuming that
interconnect available.


> +	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> +	status = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
> +
> +	speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, status);
> +	width = FIELD_GET(PCI_EXP_LNKSTA_NLW, status);
> +
> +	switch (speed) {
> +	case 1:
> +		bw = MBps_to_icc(PCIE_GEN1_BW_MBPS);
> +		break;
> +	case 2:
> +		bw = MBps_to_icc(PCIE_GEN2_BW_MBPS);
> +		break;
> +	case 3:
> +		bw = MBps_to_icc(PCIE_GEN3_BW_MBPS);
> +		break;
> +	default:
> +		dev_warn(pci->dev, "using default GEN4 bandwidth\n");
> +		fallthrough;
> +	case 4:
> +		bw = MBps_to_icc(PCIE_GEN4_BW_MBPS);
> +		break;
> +	}
> +
> +	ret = icc_set_bw(pcie_ep->icc_mem, 0, width * bw);
> +	if (ret) {
> +		dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
> +			ret);
> +	}

Are you not seeing the below warning from checkpatch?

WARNING: braces {} are not necessary for single statement blocks

> +}
> +
>  static int qcom_pcie_enable_resources(struct qcom_pcie_ep *pcie_ep)
>  {
>  	int ret;
> +	struct dw_pcie *pci = &pcie_ep->pci;
>  
>  	ret = clk_bulk_prepare_enable(pcie_ep->num_clks, pcie_ep->clks);
>  	if (ret)
> @@ -277,6 +331,20 @@ static int qcom_pcie_enable_resources(struct qcom_pcie_ep *pcie_ep)
>  	if (ret)
>  		goto err_phy_exit;
>  
> +	/*
> +	 * Some Qualcomm platforms require interconnect bandwidth constraints
> +	 * to be set before enabling interconnect clocks.
> +	 *
> +	 * Set an initial peak bandwidth corresponding to single-lane Gen 1
> +	 * for the pcie-mem path.
> +	 */
> +	ret = icc_set_bw(pcie_ep->icc_mem, 0, MBps_to_icc(PCIE_GEN1_BW_MBPS));
> +	if (ret) {
> +		dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
> +			ret);
> +		goto err_phy_exit;
> +	}
> +
>  	return 0;

Thanks,
Pavan