[PATCH v9 2/2] PCI/DPC: Disable DPC service on suspend

[Bjorn Helgaas <helgaas@kernel.org>]

From: Kai-Heng Feng <kai.heng.feng@canonical.com>

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.com
Signed-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 | 60 +++++++++++++++++++++++++++++++++---------
 1 file changed, 48 insertions(+), 12 deletions(-)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index a668820696dc..2b6ef7efa3c1 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/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 int dpc_suspend(struct pcie_device *dev)
+{
+	dpc_disable(dev);
+	return 0;
+}
+
+static int dpc_resume(struct pcie_device *dev)
+{
+	dpc_enable(dev);
+	return 0;
+}
+
 static void dpc_remove(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);
+	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,
 };
 
-- 
2.34.1