PCI/DPC: Disable DPC service on suspend

If the link is powered off during suspend, electrical noise may cause
errors that trigger DPC.  If the DPC interrupt is enabled and shares an IRQ
with PME, that causes a spurious wakeup during suspend.

Disable DPC triggering and the DPC interrupt during suspend to prevent
this.  Clear DPC interrupt status before re-enabling DPC interrupts during
resume so we don't get an interrupt for errors that occurred during the
suspend/resume process.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=209149
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216295
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218090
Link: https://lore.kernel.org/r/20240416043225.1462548-3-kai.heng.feng@canonical.comSigned-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
[bhelgaas: clear status on resume, add comments, commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pcie/dpc.c

@@ -412,13 +412,44 @@ void pci_dpc_init(struct pci_dev *pdev)
 	}
 }
 
+static void dpc_enable(struct pcie_device *dev)
+{
+	struct pci_dev *pdev = dev->port;
+	int dpc = pdev->dpc_cap;
+	u16 ctl;
+
+	/*
+	 * Clear DPC Interrupt Status so we don't get an interrupt for an
+	 * old event when setting DPC Interrupt Enable.
+	 */
+	pci_write_config_word(pdev, dpc + PCI_EXP_DPC_STATUS,
+			      PCI_EXP_DPC_STATUS_INTERRUPT);
+
+	pci_read_config_word(pdev, dpc + PCI_EXP_DPC_CTL, &ctl);
+	ctl &= ~PCI_EXP_DPC_CTL_EN_MASK;
+	ctl |= PCI_EXP_DPC_CTL_EN_FATAL | PCI_EXP_DPC_CTL_INT_EN;
+	pci_write_config_word(pdev, dpc + PCI_EXP_DPC_CTL, ctl);
+}
+
+static void dpc_disable(struct pcie_device *dev)
+{
+	struct pci_dev *pdev = dev->port;
+	int dpc = pdev->dpc_cap;
+	u16 ctl;
+
+	/* Disable DPC triggering and DPC interrupts */
+	pci_read_config_word(pdev, dpc + PCI_EXP_DPC_CTL, &ctl);
+	ctl &= ~(PCI_EXP_DPC_CTL_EN_FATAL | PCI_EXP_DPC_CTL_INT_EN);
+	pci_write_config_word(pdev, dpc + PCI_EXP_DPC_CTL, ctl);
+}
+
 #define FLAG(x, y) (((x) & (y)) ? '+' : '-')
 static int dpc_probe(struct pcie_device *dev)
 {
 	struct pci_dev *pdev = dev->port;
 	struct device *device = &dev->device;
 	int status;
-	u16 ctl, cap;
+	u16 cap;
 
 	if (!pcie_aer_is_native(pdev) && !pcie_ports_dpc_native)
 		return -ENOTSUPP;
@@ -433,11 +464,7 @@ static int dpc_probe(struct pcie_device *dev)
 	}
 
 	pci_read_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CAP, &cap);
-
-	pci_read_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, &ctl);
-	ctl &= ~PCI_EXP_DPC_CTL_EN_MASK;
-	ctl |= PCI_EXP_DPC_CTL_EN_FATAL | PCI_EXP_DPC_CTL_INT_EN;
-	pci_write_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, ctl);
+	dpc_enable(dev);
 
 	pci_info(pdev, "enabled with IRQ %d\n", dev->irq);
 	pci_info(pdev, "error containment capabilities: Int Msg #%d, RPExt%c PoisonedTLP%c SwTrigger%c RP PIO Log %d, DL_ActiveErr%c\n",
@@ -450,14 +477,21 @@ static int dpc_probe(struct pcie_device *dev)
 	return status;
 }
 
-static void dpc_remove(struct pcie_device *dev)
+static int dpc_suspend(struct pcie_device *dev)
 {
-	struct pci_dev *pdev = dev->port;
-	u16 ctl;
+	dpc_disable(dev);
+	return 0;
+}
 
-	pci_read_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, &ctl);
-	ctl &= ~(PCI_EXP_DPC_CTL_EN_FATAL | PCI_EXP_DPC_CTL_INT_EN);
-	pci_write_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, ctl);
+static int dpc_resume(struct pcie_device *dev)
+{
+	dpc_enable(dev);
+	return 0;
+}
+
+static void dpc_remove(struct pcie_device *dev)
+{
+	dpc_disable(dev);
 }
 
 static struct pcie_port_service_driver dpcdriver = {
@@ -465,6 +499,8 @@ static struct pcie_port_service_driver dpcdriver = {
 	.port_type	= PCIE_ANY_PORT,
 	.service	= PCIE_PORT_SERVICE_DPC,
 	.probe		= dpc_probe,
+	.suspend	= dpc_suspend,
+	.resume		= dpc_resume,
 	.remove		= dpc_remove,
 };