----- Original Message -----

From: "Bjorn Helgaas" <helgaas@kernel.org>
To: "Timothy Pearson" <tpearson@raptorengineering.com>
Cc: "linuxppc-dev" <redacted>, "linux-kernel" <redacted>, "linux-pci"
[off-list ref], "Madhavan Srinivasan" [off-list ref], "Michael Ellerman" [off-list ref],
"christophe leroy" [off-list ref], "Naveen N Rao" [off-list ref], "Bjorn Helgaas"
[off-list ref], "Shawn Anastasio" [off-list ref], "Lukas Wunner" [off-list ref]
Sent: Wednesday, June 18, 2025 2:44:00 PM
Subject: Re: [PATCH v2 2/6] pci/hotplug/pnv_php: Work around switches with broken

[+cc Lukas, pciehp expert]

On Wed, Jun 18, 2025 at 11:56:54AM -0500, Timothy Pearson wrote:

quoted

 presence detection

(subject/commit wrapping seems to be on all of these patches)

quoted

The Microsemi Switchtec PM8533 PFX 48xG3 [11f8:8533] PCIe switch system
was observed to incorrectly assert the Presence Detect Set bit in its
capabilities when tested on a Raptor Computing Systems Blackbird system,
resulting in the hot insert path never attempting a rescan of the bus
and any downstream devices not being re-detected.

Seems like this switch supports standard PCIe hotplug?  Quite a bit of
this driver looks similar to things in pciehp.  Is there some reason
we can't use pciehp directly?  Maybe pciehp could work if there were
hooks for the PPC-specific bits?

While that is a good long term goal that Raptor is willing to work toward, it is non-trivial and will require buy-in from other stakeholders (e.g. IBM).  If practical, I'd like to get this series merged first, to fix the broken hotplug on our hardware that is deployed worldwide, then in parallel see what can be done to merge PowerNV support into pciehp.  Would that work?