linux-kernel - Re: [PATCH v9 2/6] PCI: qcom: Add ICC bandwidth vote for CPU to PCIe path

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Message-ID: <20240407143902.GB2679@thinkpad>
Date: Sun, 7 Apr 2024 20:09:02 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
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>,
	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,
	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 v9 2/6] PCI: qcom: Add ICC bandwidth vote for CPU to PCIe
 path

On Sun, Apr 07, 2024 at 10:07:35AM +0530, Krishna chaitanya chundru wrote:
> To access PCIe registers, PCIe BAR space, config space the CPU-PCIe

Please specify whether you are referencing PCIe host controller or endpoint
device or both.

> ICC (interconnect consumers) path should be voted otherwise it may

ICC is just 'Interconnect' unless I misunderstood.

> lead to NoC (Network on chip) timeout. We are surviving because of
> other driver vote for this path.
> 

s/vote/voting

> As there is less access on this path compared to PCIe to mem path
> add minimum vote i.e 1KBps bandwidth always which is recommended
> by HW team.
> 

'which is sufficient enough to keep the path active.'

> When suspending, disable this path after register space access
> is done.
> 
> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 38 ++++++++++++++++++++++++++++++----
>  1 file changed, 34 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 14772edcf0d3..b4893214b2d3 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 +1422,19 @@ 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 interconnect bandwidth for PCIe-MEM: %d\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	/*
> +	 * Since the CPU-PCIe path is only used for activities like register

Again, differentiate PCIe controller and endpoint device access.

> +	 * access, Config/BAR space access, HW team has recommended to use a
> +	 * minimal bandwidth of 1KBps just to keep the link active.
> +	 */
> +	ret = icc_set_bw(pcie->icc_cpu, 0, kBps_to_icc(1));
> +	if (ret) {
> +		dev_err(pci->dev, "failed to set interconnect bandwidth for CPU-PCIe: %d\n",
>  			ret);
>  		return ret;
>  	}
> @@ -1448,7 +1464,7 @@ 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 interconnect bandwidth for PCIe-MEM: %d\n",
>  			ret);
>  	}
>  }
> @@ -1610,7 +1626,7 @@ 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 interconnect bandwidth for PCIe-MEM: %d\n", ret);
>  		return ret;
>  	}
>  
> @@ -1634,7 +1650,15 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>  		pcie->suspended = true;
>  	}
>  
> -	return 0;
> +	/*
> +	 * Remove the vote for CPU-PCIe path now, since at this point onwards,
> +	 * no register access will be done.
> +	 */

Are you sure? Didn't we see late access to DBI registers on sc7280?

> +	ret = icc_disable(pcie->icc_cpu);
> +	if (ret)
> +		dev_err(dev, "failed to disable icc path of CPU-PCIe: %d\n", ret);

s/failed to disable icc path/Failed to disable Interconnect path between CPU-PCIe

> +
> +	return ret;
>  }
>  
>  static int qcom_pcie_resume_noirq(struct device *dev)
> @@ -1642,6 +1666,12 @@ static int qcom_pcie_resume_noirq(struct device *dev)
>  	struct qcom_pcie *pcie = dev_get_drvdata(dev);
>  	int ret;
>  
> +	ret = icc_enable(pcie->icc_cpu);
> +	if (ret) {
> +		dev_err(dev, "failed to enable icc path of CPU-PCIe: %d\n", ret);

Same as above.

- Mani

-- 
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