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Date: Mon, 22 Apr 2024 20:01:43 +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 v10 2/6] PCI: qcom: Add ICC bandwidth vote for CPU to
 PCIe path
Message-ID: <20240422143143.GD9775@thinkpad>
References: <20240409-opp_support-v10-0-1956e6be343f@quicinc.com>
 <20240409-opp_support-v10-2-1956e6be343f@quicinc.com>
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In-Reply-To: <20240409-opp_support-v10-2-1956e6be343f@quicinc.com>

On Tue, Apr 09, 2024 at 03:43:20PM +0530, Krishna chaitanya chundru wrote:
> To access PCIe registers of the host controller and endpoint PCIe
> BAR space, config space the CPU-PCIe ICC (interconnect) path should

'To access the host controller registers and endpoint BAR/Config space,'

> 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.
> 
> In suspend to ram case there can be some DBI access. Except in suspend
> to ram case disable CPU-PCIe ICC path after register space access
> is done.
> 

During S2RAM (Suspend-to-RAM), 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>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 43 ++++++++++++++++++++++++++++++----
>  1 file changed, 39 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 14772edcf0d3..e53422171c01 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 interconnect bandwidth for PCIe-MEM: %d\n",

'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

Single space after 'a'

> +	 * 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 interconnect bandwidth for CPU-PCIe: %d\n",

'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 interconnect bandwidth for PCIe-MEM: %d\n",

'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 interconnect bandwidth for PCIe-MEM: %d\n", ret);

'Failed to set bandwidth for PCIe-MEM interconnect path: %d\n'

>  		return ret;
>  	}
>  
> @@ -1634,7 +1651,17 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>  		pcie->suspended = true;
>  	}
>  
> -	return 0;
> +	/*
> +	 * In suspend to ram case there are DBI access, except in suspend to ram case
> +	 * remove the vote for CPU-PCIe path now, since at this point onwards,
> +	 * no register access will be done.
> +	 */

	/*
	 * 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 Interconnect path of CPU-PCIe: %d\n", ret);

'Failed to disable CPU-PCIe interconnect path: %d\n'

> +	}
> +	return ret;
>  }
>  
>  static int qcom_pcie_resume_noirq(struct device *dev)
> @@ -1642,6 +1669,14 @@ 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 Interconnect path of CPU-PCIe: %d\n", ret);

'Failed to enable CPU-PCIe interconnect path: %d\n'

- Mani

-- 
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