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Date: Tue, 30 Apr 2024 10:51:25 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To: Krishna chaitanya chundru <quic_krichai@quicinc.com>
Cc: Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= <kw@linux.com>,
	Bjorn Helgaas <bhelgaas@google.com>, johan+linaro@kernel.org,
	bmasney@redhat.com, djakov@kernel.org,
	linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
	vireshk@kernel.org, quic_vbadigan@quicinc.com,
	quic_skananth@quicinc.com, quic_nitegupt@quicinc.com,
	quic_parass@quicinc.com, krzysztof.kozlowski@linaro.org,
	Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Subject: Re: [PATCH v12 2/6] PCI: qcom: Add ICC bandwidth vote for CPU to
 PCIe path
Message-ID: <20240430052125.GC3301@thinkpad>
References: <20240427-opp_support-v12-0-f6beb0a1f2fc@quicinc.com>
 <20240427-opp_support-v12-2-f6beb0a1f2fc@quicinc.com>
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In-Reply-To: <20240427-opp_support-v12-2-f6beb0a1f2fc@quicinc.com>

On Sat, Apr 27, 2024 at 07:22:35AM +0530, 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@linaro.org>
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

- Mani

> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 44 ++++++++++++++++++++++++++++++----
>  1 file changed, 40 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 14772edcf0d3..465d63b4be1c 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -245,6 +245,7 @@ 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;
> @@ -1409,6 +1410,9 @@ 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.
> @@ -1418,7 +1422,20 @@ 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);
> +		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);
>  		return ret;
>  	}
> @@ -1448,7 +1465,7 @@ 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);
>  	}
>  }
> @@ -1610,7 +1627,7 @@ 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;
>  	}
>  
> @@ -1634,7 +1651,18 @@ 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)
> @@ -1642,6 +1670,14 @@ 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)
> 
> -- 
> 2.42.0
> 

-- 
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