[PATCH v13 1/5] PCI/DPC: Ignore devices with no AER Capability

[Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>]

From: Bjorn Helgaas <bhelgaas@google.com>

Downstream Ports may support DPC regardless of whether they support AER
(see PCIe r7.0, sec 6.2.11.2).  Previously, if the user booted with
"pcie_ports=dpc-native", it was possible for dpc_probe() to succeed even if
the device had no AER Capability, but dpc_get_aer_uncorrect_severity()
depends on the AER Capability.

dpc_probe() previously failed if:

  !pcie_aer_is_native(pdev) && !pcie_ports_dpc_native
  !(pcie_aer_is_native() || pcie_ports_dpc_native)    # by De Morgan's law

so it succeeded if:

  pcie_aer_is_native() || pcie_ports_dpc_native

Fail dpc_probe() if the device has no AER Capability.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Olof Johansson <olof@lixom.net>
---
Changes since v12

 * Rebased to v7.3-rc3.  No other changes.

v12 posting
https://lore.kernel.org/all/20201126011816.711106-1-helgaas@kernel.org/

 drivers/pci/pcie/dpc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index 2b779bd1d861..4c2cfae27a08 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -477,6 +477,9 @@ static int dpc_probe(struct pcie_device *dev)
 	int status;
 	u16 cap;
 
+	if (!pdev->aer_cap)
+		return -ENOTSUPP;
+
 	if (!pcie_aer_is_native(pdev) && !pcie_ports_dpc_native)
 		return -ENOTSUPP;
 
-- 
2.43.0