Re: [PATCH v2] PCI: rzg3s-host: Re-enumerate the bus on PCIe link-state changes

On Thu, Jul 16, 2026 at 03:04:56PM +0300, Claudiu Beznea wrote:
> Hi, Mani,
> 
> On 7/14/26 19:58, Manivannan Sadhasivam wrote:
> > On Tue, Jun 30, 2026 at 02:17:20PM +0000, John Madieu wrote:
> > > The RZ/G3E PCIe controller does not expose the standard PCIe Slot
> > > Capability registers, so the generic pciehp driver cannot be used. The
> > > only link-state signal the hardware provides is the DL_UpDown bit in the
> > > PEIS0 event status register, which is raised on every Data Link layer
> > > up/down transition.
> > > 
> > > Enable DL_UpDown in PEIE0 and hook up an interrupt handler so the driver
> > > can react to link-state changes: a device that trains after boot gets
> > > enumerated, and a device that disappears on link loss is removed. This
> > > provides hotplug-like behaviour without the PCI hotplug core, which is
> > > unavailable for the reason above.
> > > 
> > > On a DL_UpDown event the handler acks the W1C status bit and schedules a
> > > worker that inspects PCSTAT1.DL_DOWN_STS:
> > > 
> > >    - link up: re-run max link speed negotiation, wait for the link to
> > >      settle and pci_rescan_bus() the root bus;
> > >    - link down: walk the bus in reverse and
> > >      pci_stop_and_remove_bus_device() each child.
> > > 
> > > Both paths take pci_lock_rescan_remove() to serialise against the PCI
> > > core.
> > > 
> > > Link events are only acted upon once the controller is fully
> > > initialised. A DL_UpDown latched while the registers are not configured,
> > > for example when the event IRQ is used as a system wakeup source during
> > > resume, is acknowledged but does not schedule a rescan.
> > This is not correct. I don't see the patch configuring 'event IRQ' as a wakeup
> > source.
> > 
> > Rest of the patch LGTM. If you confirm above, I can reword while applying.
> 
> John is not with Renesas anymore so I confirm on his behalf it is OK for you
> to amend it while applying.
> 
> However, I checked if this patch applies on top of next-20260715 or v7.2-rc1
> and it doesn't on neither of these two HEADs.
> 
> I can re-base and re-send. Please let me know otherwise.
> 

Please do so. Thanks for checking!

- Mani

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