[PATCH v4 2/2] PCI: qcom: Implement shutdown() callback

[Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>]

From: Manivannan Sadhasivam <mani@kernel.org>

PCIe host controllers should bring the link down cleanly before system
shutdown/reboot proceeds to remove power/clocks from the controller.
Without this, the link may still be up and endpoints still have
transactions in flight when power/clocks are cut, which can trip SMMU
translation faults or NoC protocol errors.

Reuse dw_pcie_suspend_noirq() in the shutdown path to force the link
into L2, putting it into D3cold.

device_shutdown() runs with interrupts enabled, unlike suspend_noirq().
Mask the chained MSI IRQ(s) and the Global IRQ before tearing down the
link and clocks/PHY, since a late/spurious interrupt could otherwise
reach a handler that touches now-unclocked PARF/DBI registers.

Firmware-managed (ECAM) Root Complexes own their own link teardown and
clock/PHY shutdown; for those, only mask the MSI IRQs.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 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 b58a607b713f..fad2f4e2d6be 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1924,6 +1924,9 @@ static int qcom_pcie_ecam_host_init(struct pci_config_window *cfg)
 	pp->use_imsi_rx = true;
 	dw_pcie_msi_init(pp);
 
+	/* Stash pci so qcom_pcie_shutdown() can mask the MSI IRQ(s) later */
+	platform_set_drvdata(to_platform_device(dev), pci);
+
 	return devm_add_action_or_reset(dev, qcom_pci_free_msi, pp);
 }
 
@@ -2337,6 +2340,55 @@ static int qcom_pcie_probe(struct platform_device *pdev)
 	return ret;
 }
 
+static void qcom_pcie_mask_msi_irqs(struct dw_pcie_rp *pp)
+{
+	u32 ctrl;
+
+	/*
+	 * Mask the chained MSI IRQ(s) before tearing down the link and
+	 * clocks/PHY. Unlike suspend_noirq(), device_shutdown() runs with
+	 * interrupts enabled, so a late/spurious MSI could otherwise hit
+	 * dw_chained_msi_isr() and touch DBI registers after the controller
+	 * is powered off.
+	 */
+	for (ctrl = 0; ctrl < MAX_MSI_CTRLS; ctrl++) {
+		if (pp->msi_irq[ctrl] > 0)
+			disable_irq(pp->msi_irq[ctrl]);
+	}
+}
+
+static void qcom_pcie_shutdown(struct platform_device *pdev)
+{
+	const struct qcom_pcie_cfg *pcie_cfg = of_device_get_match_data(&pdev->dev);
+	struct qcom_pcie *pcie;
+
+	if (pcie_cfg && pcie_cfg->firmware_managed) {
+		/*
+		 * Firmware owns the link teardown and clock/PHY shutdown in
+		 * this mode; Linux only owns the chained MSI IRQ(s), which
+		 * still need to be masked off before shutdown proceeds.
+		 */
+		struct dw_pcie *pci = platform_get_drvdata(pdev);
+
+		if (pci)
+			qcom_pcie_mask_msi_irqs(&pci->pp);
+		return;
+	}
+
+	pcie = platform_get_drvdata(pdev);
+	if (pcie) {
+		qcom_pcie_mask_msi_irqs(&pcie->pci->pp);
+
+		if (pcie->global_irq)
+			disable_irq(pcie->global_irq);
+
+		dw_pcie_suspend_noirq(pcie->pci);
+	}
+
+	pm_runtime_put_sync(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+}
+
 static int qcom_pcie_suspend_noirq(struct device *dev)
 {
 	struct qcom_pcie *pcie;
@@ -2519,5 +2571,6 @@ static struct platform_driver qcom_pcie_driver = {
 		.pm = &qcom_pcie_pm_ops,
 		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
 	},
+	.shutdown = qcom_pcie_shutdown,
 };
 builtin_platform_driver(qcom_pcie_driver);

-- 
2.34.1