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

[Lukas Wunner <lukas@wunner.de>]

On Sat, Feb 14, 2026 at 07:01:13AM +0100, Lukas Wunner wrote:
> On Fri, Feb 13, 2026 at 03:14:28PM -0800, Kuppuswamy Sathyanarayanan wrote:
> > On Intel Catlow Lake platforms, PCH PCIe root ports do not reliably
> > update PME status registers (PME Status and PME Requester_ID in the
> > Root Status register) during D3hot to D0 transitions, even though PME
> > interrupts are delivered correctly.
> 
> Hm, so in theory we could amend the PME driver to walk the bus below the
> Root Port and see if anything has PME_Status set in the PMCSR register.
> 
> But the PME interrupt is shared with hotplug, bandwidth control etc,
> so we'd end up gratuitouly (and frequently) runtime resuming switches
> below the Root Port to see if there's anything below which is requesting
> wakeup.
> 
> So just keeping the Root Port runtime resumed all the time, as this
> patch does, is still a better approach IMO.
> 
> I'm wondering though if this causes a power regression.  Does keeping
> the Root Port in D0 prevent the Package from entering a lower power
> state?  Or is this irrelevant because the PCH is a different chip
> or tile?

I've just realized that pcie_disable_interrupt() isn't called from
pciehp_suspend() if pme_is_native() is true.  Should disabling
runtime PM cause a power regression, an alternative solution may be
to make pcie_disable_interrupt() conditional on a new pme_is_broken()
which checks for affected Catlow Lake PCH Root Ports.

The pm_runtime_disable() approach is slightly preferred because
it keeps pciehp code clean.

Thanks,

Lukas