UBUNTU: SAUCE: PCI/DPC: Disable DPC interrupt during suspend

BugLink: https://bugs.launchpad.net/bugs/1913691

Commit 5031060 ("iommu/vt-d: Enable PCI ACS for platform opt in
hint") enables ACS, and some platforms lose its NVMe after resume from
firmware:
[   50.947816] pcieport 0000:00:1b.0: DPC: containment event, status:0x1f01 source:0x0000
[   50.947817] pcieport 0000:00:1b.0: DPC: unmasked uncorrectable error detected
[   50.947829] pcieport 0000:00:1b.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Receiver ID)
[   50.947830] pcieport 0000:00:1b.0:   device [8086:06ac] error status/mask=00200000/00010000
[   50.947831] pcieport 0000:00:1b.0:    [21] ACSViol                (First)
[   50.947841] pcieport 0000:00:1b.0: AER: broadcast error_detected message
[   50.947843] nvme nvme0: frozen state error detected, reset controller

Like what previous patch does to AER, introduce new helpers to disable
DPC interrupt and enable it on system suspend and resume, respectively.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=209149
Fixes: 5031060 ("iommu/vt-d: Enable PCI ACS for platform opt in hint")
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Timo Aaltonen <timo.aaltonen@canonical.com>

drivers/pci/pcie/dpc.c

@@ -279,13 +279,34 @@ void pci_dpc_init(struct pci_dev *pdev)
 	}
 }
 
+static void dpc_enable(struct pcie_device *dev)
+{
+	struct pci_dev *pdev = dev->port;
+	u16 ctl;
+
+	pci_read_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, &ctl);
+
+	ctl = (ctl & 0xfff4) | 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 void dpc_disable(struct pcie_device *dev)
+{
+	struct pci_dev *pdev = dev->port;
+	u16 ctl;
+
+	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);
+}
+
 #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;
@@ -300,10 +321,7 @@ 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 = (ctl & 0xfff4) | 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",
@@ -316,21 +334,30 @@ 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 = {
 	.name		= "dpc",
 	.port_type	= PCIE_ANY_PORT,
 	.service	= PCIE_PORT_SERVICE_DPC,
 	.probe		= dpc_probe,
+	.suspend	= dpc_suspend,
+	.resume		= dpc_resume,
 	.remove		= dpc_remove,
 };