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

[Yazen Ghannam]

On Tue, Oct 20, 2026 at 11:19:19AM -0700, Kuppuswamy Sathyanarayanan wrote:
> From: Lukas Wunner <lukas@xxxxxxxxx>
> 
> 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@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v5.8+

Another open question from the other set:
https://lore.kernel.org/all/02a33171-b901-400b-921a-c40fe167b424@xxxxxxxxxxxxxxx/

Maybe the issue is more about how to handle the Fixes tag?

The recent commit is where this seems to functionally break.

The older commit is where this logically broke. 

> ---
>  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);
> -- 

But I agree this is okay otherwise.

Reviewed-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>

Thanks,
Yazen