Re: [PATCH v2 5/6] PCI/ACPI: Request DPC control only together with AER control

[Kuppuswamy Sathyanarayanan]

Hi,

On 11/4/2026 8:13 AM, Yazen Ghannam wrote:
> On Tue, Oct 20, 2026 at 11:19:22AM -0700, Kuppuswamy Sathyanarayanan 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.
> 
> What about folding this last line into the rest of the comment above?
> 
> Or maybe just drop the spec details and leave that for the commit
> message?

I'll fold it into the comment above in v3.

> 
>>  	 */
>> -	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;
>> -- 
> 
> Otherwise, looks good to me.
> 
> Reviewed-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>

Thanks.

> 
> Thanks,
> Yazen

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer