[Skiboot] PowerNV PCIe hotplug support?

[Mahesh J Salgaonkar]

On 2024-05-14 18:09:17 Tue, Dan Horák wrote:
> On Thu, 28 Dec 2023 13:31:53 -0600 (CST)
> Timothy Pearson <tpearson at raptorengineering.com> wrote:
> 
> > Resend to skiboot since I think skiboot is actually responsible for trying to bring the links back up / providing new DT information to Linux:
> > 
> > I've been evaluating some new options for our POWER9-based hardware in the NVMe space, and would like some clarification on the current status of PCIe hotplug for the PowerNV platforms.
> > 
> > From what I understand, the pnv_php driver provides the basic hotplug functionality on PowerNV.  What I'm not clear on is to what extent this is intended to flow downstream to attached PCIe switches.
> > 
> > I have a test setup here that consists of a PMC 8533 switch and several downstream NVMe drives, with the switch attached directly to the PHB4 root port.  After loading the pnv_php module, I can disconnect the downstream NVMe devices by either using echo 0 on /sys/bus/pcu/slots/Snnnnnnn/power, or by doing a physical surprise unplug, however nothing I try can induce a newly plugged device to train and be detected on the bus.  Even trying a echo 0 and subsequent echo 1 to /sys/bus/pcu/slots/Snnnnnnn/power only results in the device going offline, there seems to be no way to bring the device back online short of a reboot.
> > 
> > Hotplug of other devices connected directly to the PHB4 appears to work properly (I can online and offline via the power node); the issue seems to be restricted to downstream devices connected to the (theoretically hotplug capable) PMC 8533 switch.
> > 
> > Is this the intended behavior for downstream (non-IBM) PCIe ports?  Raptor can provide resources to assist in a fix if needed, but I would like to understand if this is a bug or an unimplemented feature first, and if the latter what the main issues are likely to be in implementation.
> 
> isn't
> https://lists.ozlabs.org/pipermail/linuxppc-dev/2024-May/271751.html
> fixing the issue mentioned here?

Yes, that series is targeted to fix the issue that Timothy reported.

Timothy, Did you get chance to try the fix ?

Thanks,
-Mahesh.

> 
> 
> 		Dan
> _______________________________________________
> Skiboot mailing list
> Skiboot at lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/skiboot

-- 
Mahesh J Salgaonkar