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

[Claudiu Beznea <claudiu.beznea+renesas@tuxon.dev>]

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.

Thank you,
Claudiu