[PATCH v5 3/3] PCI/DPC: Disable DPC interrupt during suspend

[Kai-Heng Feng <kai.heng.feng@canonical.com>]

PCIe service that shares IRQ with PME may cause spurious wakeup on
system suspend.

Since AER is conditionally disabled in previous patch, also apply the
same logic to disable DPC which depends on AER to work.

It's okay to disable DPC because PCIe Base Spec 5.0, section 5.2 "Link
State Power Management" states that TLP and DLLP transmission is
disabled for a Link in L2/L3 Ready (D3hot), L2 (D3cold with aux power)
and L3 (D3cold), hence we don't lose much here to disable DPC during system
suspend.

[1] https://lore.kernel.org/linux-pci/20220408153159.106741-1-kai.heng.feng@canonical.com/
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216295

Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
v5:
 - Wording.

v4:
v3:
 - No change.

v2:
 - Only disable DPC IRQ.
 - No more check on PME IRQ#.
 drivers/pci/pcie/dpc.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index 3ceed8e3de41..d2d845c20438 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -384,6 +384,30 @@ static int dpc_probe(struct pcie_device *dev)
 	return status;
 }
 
+static int dpc_suspend(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_INT_EN;
+	pci_write_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, ctl);
+
+	return 0;
+}
+
+static int dpc_resume(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_INT_EN;
+	pci_write_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, ctl);
+
+	return 0;
+}
+
 static void dpc_remove(struct pcie_device *dev)
 {
 	struct pci_dev *pdev = dev->port;
@@ -399,6 +423,8 @@ 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