[L/M/Unstable] [PATCH 2/2] UBUNTU: SAUCE: PCI/DPC: Disable DPC service during suspend, again

[Kai-Heng Feng]

BugLink: https://bugs.launchpad.net/bugs/2033025

When the power rail gets cut off, the hardware can create some electric
noise on the link that triggers AER. If IRQ is shared between AER with
PME, such AER noise will cause a spurious wakeup on system suspend.

When the power rail gets back, the firmware of the device resets itself
and can create unexpected behavior like sending PTM messages. For this
case, the driver will always be too late to toggle off features should
be disabled.

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 if
the power will be turned off during suspend process, disable DPC service
and re-enable it during the resume process. This should not affect the
basic functionality.

Since DPC depends on AER to function, also disable DPC.

This patch was in the Ubuntu kernel but was dropped later in the hope of
upstream version would come to light soon. However, the patch is still
under discussion, and PCI maintainer and reviewers don't have a
concensus on the final approach (D3hot vs D3cold), so let's reinstate
the fix until upstream has a final version.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=209149
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216295
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
 drivers/pci/pcie/dpc.c | 49 ++++++++++++++++++++++++++++++++----------
 1 file changed, 38 insertions(+), 11 deletions(-)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index 3ceed8e3de41..47782c7bbb87 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -347,13 +347,34 @@ 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;
@@ -368,10 +389,7 @@ 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",
@@ -384,14 +402,21 @@ 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 = {
@@ -399,6 +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