Date: Fri, 14 Jun 2024 15:14:10 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Krishna chaitanya chundru <quic_krichai@...cinc.com>
cc: Bjorn Andersson <andersson@...nel.org>, 
    Konrad Dybcio <konrad.dybcio@...aro.org>, Rob Herring <robh@...nel.org>, 
    Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
    Conor Dooley <conor+dt@...nel.org>, 
    Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
    Lorenzo Pieralisi <lpieralisi@...nel.org>, 
    Krzysztof Wilczyński <kw@...ux.com>, 
    Bjorn Helgaas <bhelgaas@...gle.com>, johan+linaro@...nel.org, 
    bmasney@...hat.com, djakov@...nel.org, 
    Krzysztof Kozlowski <krzk+dt@...nel.org>, linux-arm-msm@...r.kernel.org, 
    devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
    linux-pci@...r.kernel.org, vireshk@...nel.org, quic_vbadigan@...cinc.com, 
    quic_skananth@...cinc.com, quic_nitegupt@...cinc.com, 
    quic_parass@...cinc.com, krzysztof.kozlowski@...aro.org, 
    Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Subject: Re: [PATCH v14 1/4] PCI: qcom: Add ICC bandwidth vote for CPU to
 PCIe path

On Sun, 9 Jun 2024, Krishna chaitanya chundru wrote:

> To access the host controller registers of the host controller and the
> endpoint BAR/config space, the CPU-PCIe ICC (interconnect) path should
> be voted otherwise it may lead to NoC (Network on chip) timeout.
> We are surviving because of other driver voting for this path.
> 
> As there is less access on this path compared to PCIe to mem path
> add minimum vote i.e 1KBps bandwidth always which is sufficient enough
> to keep the path active and is recommended by HW team.
> 
> During S2RAM (Suspend-to-RAM), the DBI access can happen very late (while
> disabling the boot CPU). So do not disable the CPU-PCIe interconnect path
> during S2RAM as that may lead to NoC error.
> 
> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 45 +++++++++++++++++++++++++++++++---
>  1 file changed, 41 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 5f9f0ff19baa..ff1d891c8b9a 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -253,6 +253,7 @@ struct qcom_pcie {
>  	struct phy *phy;
>  	struct gpio_desc *reset;
>  	struct icc_path *icc_mem;
> +	struct icc_path *icc_cpu;
>  	const struct qcom_pcie_cfg *cfg;
>  	struct dentry *debugfs;
>  	bool suspended;
> @@ -1369,6 +1370,9 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
>  	if (IS_ERR(pcie->icc_mem))
>  		return PTR_ERR(pcie->icc_mem);
>  
> +	pcie->icc_cpu = devm_of_icc_get(pci->dev, "cpu-pcie");
> +	if (IS_ERR(pcie->icc_cpu))
> +		return PTR_ERR(pcie->icc_cpu);
>  	/*
>  	 * Some Qualcomm platforms require interconnect bandwidth constraints
>  	 * to be set before enabling interconnect clocks.
> @@ -1378,11 +1382,25 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
>  	 */
>  	ret = icc_set_bw(pcie->icc_mem, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));
>  	if (ret) {
> -		dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
> +		dev_err(pci->dev, "Failed to set bandwidth for PCIe-MEM interconnect path: %d\n",
>  			ret);

I think it would be better to separate these message clarifications into a 
separate patch. It would make both patches more into the point.

Other than that, the change looked okay to me.

-- 
 i.

>  		return ret;
>  	}
>  
> +	/*
> +	 * Since the CPU-PCIe path is only used for activities like register
> +	 * access of the host controller and endpoint Config/BAR space access,
> +	 * HW team has recommended to use a minimal bandwidth of 1KBps just to
> +	 * keep the path active.
> +	 */
> +	ret = icc_set_bw(pcie->icc_cpu, 0, kBps_to_icc(1));
> +	if (ret) {
> +		dev_err(pci->dev, "Failed to set bandwidth for CPU-PCIe interconnect path: %d\n",
> +			ret);
> +		icc_set_bw(pcie->icc_mem, 0, 0);
> +		return ret;
> +	}
> +
>  	return 0;
>  }
>  
> @@ -1408,7 +1426,7 @@ static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
>  
>  	ret = icc_set_bw(pcie->icc_mem, 0, width * QCOM_PCIE_LINK_SPEED_TO_BW(speed));
>  	if (ret) {
> -		dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
> +		dev_err(pci->dev, "Failed to set bandwidth for PCIe-MEM interconnect path: %d\n",
>  			ret);
>  	}
>  }
> @@ -1570,7 +1588,7 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>  	 */
>  	ret = icc_set_bw(pcie->icc_mem, 0, kBps_to_icc(1));
>  	if (ret) {
> -		dev_err(dev, "Failed to set interconnect bandwidth: %d\n", ret);
> +		dev_err(dev, "Failed to set bandwidth for PCIe-MEM interconnect path: %d\n", ret);
>  		return ret;
>  	}
>  
> @@ -1594,7 +1612,18 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>  		pcie->suspended = true;
>  	}
>  
> -	return 0;
> +	/*
> +	 * Only disable CPU-PCIe interconnect path if the suspend is non-S2RAM.
> +	 * Because on some platforms, DBI access can happen very late during the
> +	 * S2RAM and a non-active CPU-PCIe interconnect path may lead to NoC
> +	 * error.
> +	 */
> +	if (pm_suspend_target_state != PM_SUSPEND_MEM) {
> +		ret = icc_disable(pcie->icc_cpu);
> +		if (ret)
> +			dev_err(dev, "Failed to disable CPU-PCIe interconnect path: %d\n", ret);
> +	}
> +	return ret;
>  }
>  
>  static int qcom_pcie_resume_noirq(struct device *dev)
> @@ -1602,6 +1631,14 @@ static int qcom_pcie_resume_noirq(struct device *dev)
>  	struct qcom_pcie *pcie = dev_get_drvdata(dev);
>  	int ret;
>  
> +	if (pm_suspend_target_state != PM_SUSPEND_MEM) {
> +		ret = icc_enable(pcie->icc_cpu);
> +		if (ret) {
> +			dev_err(dev, "Failed to enable CPU-PCIe interconnect path: %d\n", ret);
> +			return ret;
> +		}
> +	}
> +
>  	if (pcie->suspended) {
>  		ret = qcom_pcie_host_init(&pcie->pci->pp);
>  		if (ret)
> 
> 

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