[PATCH v2 1/1] PCI: qcom: Add support for system suspend and resume

[Manivannan Sadhasivam]

During the system suspend, vote for minimal interconnect bandwidth and
also turn OFF the resources like clock and PHY if there are no active
devices connected to the controller. For the controllers with active
devices, the resources are kept ON as removing the resources will
trigger access violation during the late end of suspend cycle as kernel
tries to access the config space of PCIe devices to mask the MSIs.

Also, it is not desirable to put the link into L2/L3 state as that
implies VDD supply will be removed and the devices may go into powerdown
state. This will affect the lifetime of storage devices like NVMe.

And finally, during resume, turn ON the resources if the controller was
truly suspended (resources OFF) and update the interconnect bandwidth
based on PCIe Gen speed.

Suggested-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
Acked-by: Dhruva Gole <d-gole@xxxxxx>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 53 ++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index a232b04af048..7147f0103026 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -227,6 +227,7 @@ struct qcom_pcie {
 	struct gpio_desc *reset;
 	struct icc_path *icc_mem;
 	const struct qcom_pcie_cfg *cfg;
+	bool suspended;
 };
 
 #define to_qcom_pcie(x)		dev_get_drvdata((x)->dev)
@@ -1820,6 +1821,53 @@ static int qcom_pcie_probe(struct platform_device *pdev)
 	return ret;
 }
 
+static int qcom_pcie_suspend_noirq(struct device *dev)
+{
+	struct qcom_pcie *pcie = dev_get_drvdata(dev);
+	int ret;
+
+	/* Set minimum bandwidth required to keep data path functional during suspend */
+	ret = icc_set_bw(pcie->icc_mem, 0, MBps_to_icc(250));
+	if (ret) {
+		dev_err(pcie->pci->dev, "Failed to set interconnect bandwidth: %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * Turn OFF the resources only for controllers without active PCIe devices. For controllers
+	 * with active devices, the resources are kept ON and the link is expected to be in L0/L1
+	 * (sub)states.
+	 *
+	 * Turning OFF the resources for controllers with active PCIe devices will trigger access
+	 * violation during the end of the suspend cycle, as kernel tries to access the PCIe devices
+	 * config space for masking MSIs.
+	 *
+	 * Also, it is not desirable to put the link into L2/L3 state as that implies VDD supply
+	 * will be removed and the devices may go into powerdown state. This will affect the
+	 * lifetime of the storage devices like NVMe.
+	 */
+	if (!dw_pcie_link_up(pcie->pci)) {
+		qcom_pcie_host_deinit(&pcie->pci->pp);
+		pcie->suspended = true;
+	}
+
+	return 0;
+}
+
+static int qcom_pcie_resume_noirq(struct device *dev)
+{
+	struct qcom_pcie *pcie = dev_get_drvdata(dev);
+
+	if (pcie->suspended) {
+		qcom_pcie_host_init(&pcie->pci->pp);
+		pcie->suspended = false;
+	}
+
+	qcom_pcie_icc_update(pcie);
+
+	return 0;
+}
+
 static const struct of_device_id qcom_pcie_match[] = {
 	{ .compatible = "qcom,pcie-apq8064", .data = &cfg_2_1_0 },
 	{ .compatible = "qcom,pcie-apq8084", .data = &cfg_1_0_0 },
@@ -1856,12 +1904,17 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x0302, qcom_fixup_class);
 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x1000, qcom_fixup_class);
 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x1001, qcom_fixup_class);
 
+static const struct dev_pm_ops qcom_pcie_pm_ops = {
+	NOIRQ_SYSTEM_SLEEP_PM_OPS(qcom_pcie_suspend_noirq, qcom_pcie_resume_noirq)
+};
+
 static struct platform_driver qcom_pcie_driver = {
 	.probe = qcom_pcie_probe,
 	.driver = {
 		.name = "qcom-pcie",
 		.suppress_bind_attrs = true,
 		.of_match_table = qcom_pcie_match,
+		.pm = &qcom_pcie_pm_ops,
 	},
 };
 builtin_platform_driver(qcom_pcie_driver);
-- 
2.25.1