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

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Date: Sun, 7 Apr 2024 10:07:35 +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 v9 2/6] PCI: qcom: Add ICC bandwidth vote for CPU to PCIe
 path

To access PCIe registers, PCIe BAR space, config space the CPU-PCIe
ICC (interconnect consumers) path should be voted otherwise it may
lead to NoC (Network on chip) timeout. We are surviving because of
other driver vote 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 recommended
by HW team.

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
+	 * 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.
+	 */
+	ret = icc_disable(pcie->icc_cpu);
+	if (ret)
+		dev_err(dev, "failed to disable icc path of CPU-PCIe: %d\n", ret);
+
+	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);
+		return ret;
+	}
+
 	if (pcie->suspended) {
 		ret = qcom_pcie_host_init(&pcie->pci->pp);
 		if (ret)

-- 
2.42.0