[PATCH 0/6] PCI: dwc: Revert Link Up IRQ support

[Manivannan Sadhasivam]

On Tue, Nov 11, 2025 at 12:08:59PM +0100, Lukas Wunner wrote:
> On Tue, Nov 11, 2025 at 11:51:00AM +0100, Niklas Cassel wrote:
> > Revert all patches related to pcie-designware Root Complex Link Up IRQ
> > support.
> > 
> > While this fake hotplugging was a nice idea, it has shown that this feature
> > does not handle PCIe switches correctly:
> [...]
> > During the initial scan, PCI core doesn't see the switch and since the Root
> > Port is not hot plug capable, the secondary bus number gets assigned as the
> > subordinate bus number. This means, the PCI core assumes that only one bus
> > will appear behind the Root Port since the Root Port is not hot plug
> > capable.
> > 
> > This works perfectly fine for PCIe endpoints connected to the Root Port,
> > since they don't extend the bus. However, if a PCIe switch is connected,
> > then there is a problem when the downstream busses starts showing up and
> > the PCI core doesn't extend the subordinate bus number after initial scan
> > during boot.
> 
> In principle it is possible to set the is_hotplug_bridge flag on the
> bridge to force allocation of more buses.  We've already got a quirk
> to set the flag on a Conventional PCI bridge whose hotplug capability
> cannot be discovered otherwise (see quirk_hotplug_bridge() in
> drivers/pci/quirks.c).

But here, the bridges are not hotplug capable at all. They do not support the
PCI Hot-Plug Specification. So setting the flag would be incorrect.

- Mani

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