On Wed, Apr 16, 2025 at 05:06:23PM +0200, Lukas Wunner wrote:
> On Tue, Apr 15, 2025 at 02:51:42PM -0600, Keith Busch wrote:
> > On Thu, Apr 10, 2025 at 05:27:10PM +0200, Lukas Wunner wrote:
> > > First of all, PCIe hotplug is deliberately ignoring link events occurring
> > > as a side effect of Downstream Port Containment. But it's not yet ignoring
> > > Presence Detect Changed events. These can happen if a hotplug bridge uses
> > > in-band presence detect. Reported by Keith Busch, patch [1/2] seeks to
> > > fix it.
> >
> > There are switches that let you
> > toggle downstream connections to change what's attached and it causes a
> > DPC event, swapping out the downstream device at the same time. So this
> > change has the pci driver resume with the wrong device if you happen to
> > be in such a situation. I don't have such switches anymore
>
> What's the error type causing the DPC event? Surprise Down?
>
> Since commit 2ae8fbbe1cd4 ("PCI/DPC: Ignore Surprise Down error on hot
> removal"), which went into v6.9, the DPC driver handles Surprise Down
> silently and it tells the hotplug driver *not* to ignore the hotplug
> event. It does that by unconditionally clearing the PCI_DPC_RECOVERED
> flag at the end of dpc_handle_surprise_removal().
>
> Hence in the situation you're describing, the hotplug driver should
> always bring down the slot and bring it back up with the new device.
I think you're right, thank you for the pointers.
