[PCIe spec question] How to get PCI express link up / link down notifications?

[Rajat Jain]

Hello Greg,

> 
> On Fri, Oct 04, 2013 at 01:40:49AM +0000, Rajat Jain wrote:
> > Hello,
> >
> > I have a HW which is not compliant with the PCI Express hot-plug (as
> > described in the PCI express spec) because the HP signals from the
> > downstream port are simply not connected. And I have a PCI express
> > endpoint, that in the course of its life, will routinely undergo
> > power-off and power-on on cycles. Hence the PCIe link to this device
> > is expected to come down, and come up as part of regular operation.
> 
> What hardware is this?  Why not ask the manufacturer of it as they are
> the ones in control of this type of thing.

OK, Understood :-).

Actually my question was generic. For e.g. say I have a topology where root port connects to a PCIe switch-1 that in turn connects to a PCIe switch-2. My question is if the PCIe link between the switch-1 and switch-2 goes down or up for some reason (say a power fault, or due to RESET pin assertion on the switch etc), is there a way to get notification interrupt at the root port or CPU? Essentially I am looking for a notification from downstream port of switch-1, that it saw a change in the link status.

> 
> > I'm reading the PCI express spec trying to understand if it is
> > possible to get notification interrupts, whenever the PCIe link to
> > this device goes down or goes up. Can someone please help me
> > understand if it is possible?
> 
> Notification where?

Notification to the CPU via the root port.

Thanks a bunch,

Rajat

> 
> thanks,
> 
> greg k-h
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