[PATCH v6 3/3] PCI/DPC: Disable DPC interrupt during suspend

[Kai-Heng Feng]

PCIe services that share an IRQ with PME, such as AER or DPC, may cause a
spurious wakeup on system suspend. Since DPC depends on AER to work, disable
DPC interrupt notification during the system suspend process as AER interrupt
notification is already disabled by previous patch.

As Per PCIe Base Spec 5.0, section 5.2, titled "Link State Power Management",
TLP and DLLP transmission are disabled for a Link in L2/L3 Ready (D3hot), L2
(D3cold with aux power) and L3 (D3cold) states. So disabling the DPC
notification during suspend and re-enabling them during the resume process
should not affect the basic functionality.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216295
Reviewed-by: Mika Westerberg <mika.westerberg at linux.intel.com>
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
v6:
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