linux-kernel - [PATCH v10 2/6] PCI: qcom: Add ICC bandwidth vote for CPU to PCIe path

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Date: Tue, 9 Apr 2024 15:43:20 +0530
From: Krishna chaitanya chundru <quic_krichai@...cinc.com>
To: 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>
CC: <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>, <quic_krichai@...cinc.com>,
        <krzysztof.kozlowski@...aro.org>,
        Bryan O'Donoghue
	<bryan.odonoghue@...aro.org>
Subject: [PATCH v10 2/6] PCI: qcom: Add ICC bandwidth vote for CPU to PCIe
 path

To access PCIe registers of the host controller and endpoint PCIe
BAR space, 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.

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.

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 | 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",
+			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 interconnect bandwidth for CPU-PCIe: %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",
 			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);
 		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.
+	 */
+	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);
+	}
+	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);
+			return ret;
+		}
+	}
+
 	if (pcie->suspended) {
 		ret = qcom_pcie_host_init(&pcie->pci->pp);
 		if (ret)

-- 
2.42.0