[PATCH v2 2/6] PCI/DPC: Reinstate support for AER-incapable ports

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

From: Lukas Wunner <lukas@wunner.de>

Downstream Port Containment does not mandate presence of an Advanced Error
Reporting capability, so a Downstream Port may support DPC, but not AER
(PCIe r7.1 sec 6.2.11.2).

Commit 708b20003624 ("PCI/AER: Remove HEST/FIRMWARE_FIRST parsing for AER
ownership") seemingly inadvertently constrained DPC to AER-supporting
Downstream Ports by inserting a call to pcie_aer_is_native() in
dpc_probe(), which implicitly checks for presence of an AER capability.

Drop the call.  It is superfluous because it duplicates the conditions
applied by the PCIe port service driver when it decides whether to
instantiate a DPC port service (see get_port_device_capability()).
If the conditions are not met, no port service is instantiated and
dpc_probe() isn't executed.

The only difference between the conditions in dpc_probe() and the ones in
get_port_device_capability() is the check for the AER capability, so by
removing the checks from dpc_probe(), DPC is supported on AER-incapable
Downstream Ports again.

Fixes: 708b20003624 ("PCI/AER: Remove HEST/FIRMWARE_FIRST parsing for AER ownership")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org # v5.8+
---
 drivers/pci/pcie/dpc.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index 793a799053f1..104ff2b91f1f 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -474,9 +474,6 @@ static int dpc_probe(struct pcie_device *dev)
 	int status;
 	u16 cap;
 
-	if (!pcie_aer_is_native(pdev) && !pcie_ports_dpc_native)
-		return -ENOTSUPP;
-
 	status = devm_request_threaded_irq(device, dev->irq, dpc_irq,
 					   dpc_handler, IRQF_SHARED,
 					   "pcie-dpc", pdev);
-- 
2.43.0