Re: [PATCH v2] PCI: pciehp: Fix hotplug on Catlow Lake with unreliable PME status

[Kuppuswamy Sathyanarayanan]

Hi,

On 2/19/2026 3:09 AM, Rafael J. Wysocki wrote:
> On Thu, Feb 19, 2026 at 9:04 AM Lukas Wunner <lukas@xxxxxxxxx> wrote:
>>
>> On Wed, Feb 18, 2026 at 06:33:15PM +0100, Rafael J. Wysocki wrote:
>>> First, keeping the ports in D0 may gate runtime PC10.  Does it not?
>>
>> The Root Port in question is on the PCH.  I'm not sure, does keeping a
>> PCH Root Port in D0 also prevent PC10 entry or is that only the case
>> for Root Ports on the CPU die/tile?
> 
> If it is located in the PCH, it should not gate PC10 if in D0 at least
> in theory, but it would be good to verify that.
> 
> Of course, it will still gate S0ix entry through runtime idle, but
> that's a bit moot if the platform is unable to enter S0ix through
> runtime idle anyway for other reasons (which is quite likely), or if
> the power difference between S0ix and PC10 is small.

I will gather current PC10 and S0ix numbers. If there is a significant
difference between the two power savings, I will implement the
pme_is_broken() approach.


> 
>> If this does cause a power regression, the pme_is_broken() approach
>> suggested upthread might be a viable alternative.  It'll allow the
>> Root Port to go to D3hot but will keep interrupts enabled in the
>> Slot Control register.
> 
> Sounds reasonable to me.

Sounds good. 

> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer