[PATCH v3 2/2] PCI/DPC: Use _OSC to determine DPC support

[Jon Derrick]

After a5bf8719af: "PCI/AER: Use only _OSC to determine AER ownership",
_OSC is the primary determiner of ownership of Firmware First error
handling rather than HEST.

With the addition of DPC to _OSC [1], OSPM is able to negotiate DPC
services from Firmware. ACPI Root Bus enumeration sets the Host Bridge's
Native DPC flag on negotiation of those service. This patch changes DPC
probing to check DPC control as determined by _OSC, by checking the Host
Bridge's Native DPC member.

As most older platforms won't have DPC negotiable by _OSC, this patch
doesn't attempt to change behavior that assumes if OSPM has negotiated
AER by _OSC, OSPM will also want DPC control.

[1] https://members.pcisig.com/wg/PCI-SIG/document/12888

Signed-off-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
---
 drivers/pci/pcie/dpc.c          | 3 ---
 drivers/pci/pcie/portdrv_core.c | 3 ++-
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index 7621704..9104929 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -284,9 +284,6 @@ static int dpc_probe(struct pcie_device *dev)
 	int status;
 	u16 ctl, cap;
 
-	if (pcie_aer_get_firmware_first(pdev) && !pcie_ports_dpc_native)
-		return -ENOTSUPP;
-
 	status = devm_request_threaded_irq(device, dev->irq, dpc_irq,
 					   dpc_handler, IRQF_SHARED,
 					   "pcie-dpc", pdev);
diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index 50a9522..f2139a1 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -256,7 +256,8 @@ static int get_port_device_capability(struct pci_dev *dev)
 	 */
 	if (pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DPC) &&
 	    pci_aer_available() &&
-	    (pcie_ports_dpc_native || (services & PCIE_PORT_SERVICE_AER)))
+	    (pcie_ports_dpc_native || host->native_dpc ||
+	     (services & PCIE_PORT_SERVICE_AER)))
 		services |= PCIE_PORT_SERVICE_DPC;
 
 	if (pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM ||
-- 
1.8.3.1