Re: [PATCH v2 4/6] PCI/portdrv: Don't require AER to bind DPC service

[Yazen Ghannam]

On Tue, Oct 20, 2026 at 11:19:21AM -0700, Kuppuswamy Sathyanarayanan wrote:
> get_port_device_capability() binds the DPC service only if
> pci_aer_available() is true.  pci_aer_available() is false with
> "pci=noaer" or when MSI is disabled.
> 
> The DPC driver does not need either of these.  pci_aer_available()
> depends on MSI only because the AER driver does not work with INTx
> (commit 3e77a3f7895e ("PCI: Disable AER with pci=nomsi")).  The DPC
> driver does not depend on MSI or on the AER driver, and it works on
> ports without an AER capability.
> 
> PCIe r7.0 sec 6.2.11 recommends that the OS link control of DPC to
> control of AER.  PCI Firmware r3.3, sec 4.5.2.4, requires the same for
> _OSC.  Both are about ownership, not about using the AER driver.
> host->native_aer and the _OSC negotiation already cover ownership.
> 
> Drop the pci_aer_available() check.
> 
> The changes in behavior are:
> 
>   - ACPI systems booted with "pci=noaer" or with MSI disabled, and with
>     "pcie_ports=native" or "pcie_ports=dpc-native".  The OS now uses DPC
>     there, which is what those options ask for.  Without them nothing
>     changes, because the OS does not request AER control in _OSC, so
>     host->native_aer is not set.
> 
>   - Non-ACPI systems booted with "pci=noaer" or with MSI disabled.
>     host->native_aer is set there, so the OS now uses DPC.  An
>     uncorrectable error that used to be ignored with "pci=noaer" now
>     triggers DPC, which takes the link down and resets the devices below
>     the port.
> 
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> ---
>  drivers/pci/pcie/portdrv.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/portdrv.c b/drivers/pci/pcie/portdrv.c
> index 32fc623dd410..b77680fd3b75 100644
> --- a/drivers/pci/pcie/portdrv.c
> +++ b/drivers/pci/pcie/portdrv.c
> @@ -263,7 +263,6 @@ static int get_port_device_capability(struct pci_dev *dev)
>  	 * permission to use AER.
>  	 */
>  	if (pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DPC) &&
> -	    pci_aer_available() &&
>  	    (pcie_ports_dpc_native || host->native_aer))
>  		services |= PCIE_PORT_SERVICE_DPC;
>  
> -- 

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

Thanks,
Yazen