[PATCH v3 4/4] 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.

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), so we don't lose
much here to disable DPC during system suspend.

This is very similar to previous attempts to suspend AER and DPC [1],
but with a different reason.

[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>
---
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 a5d7c69b764e..98bdefde6df1 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -385,6 +385,30 @@ 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;
@@ -400,6 +424,8 @@ 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