Re: [PATCH 3/4] PCI/ACPI: Request DPC control only together with AER control

[Rafael J. Wysocki (Intel)]

On Wed, Oct 7, 2026 at 6:58 PM Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> wrote:
>
> PCI Firmware r3.3, sec 4.5.2.4, requires the OS to request AER control
> when it requests DPC control.  calculate_control() requests DPC control
> whenever CONFIG_PCIE_DPC is enabled, even if it does not request AER
> control, e.g., with "pci=noaer" or when MSI is disabled.
>
> Request DPC control only if AER control is also requested.
>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>

Acked-by: Rafael J. Wysocki (Intel) <rafael@xxxxxxxxxx>

> ---
>  drivers/acpi/pci_root.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index b0e0b33e3254..5c674d5b6bb8 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -516,8 +516,12 @@ static u32 calculate_control(void)
>          * the PCI Firmware Spec, r3.2, sec 4.5.1, table 4-5,
>          * OSC_PCI_EXPRESS_DPC_CONTROL indicates the OS supports both DPC
>          * and EDR.  EDR is always built with DPC on ACPI systems.
> +        *
> +        * PCI Firmware r3.3, sec 4.5.2.4, requires the OS to request AER
> +        * control while requesting DPC control.
>          */
> -       if (IS_ENABLED(CONFIG_PCIE_DPC))
> +       if (IS_ENABLED(CONFIG_PCIE_DPC) &&
> +           (control & OSC_PCI_EXPRESS_AER_CONTROL))
>                 control |= OSC_PCI_EXPRESS_DPC_CONTROL;
>
>         return control;
> --
> 2.43.0
>