Re: [PATCH] PCI: Always lift 2.5GT/s restriction in PCIe failed link retraining

[Bjorn Helgaas]

On Fri, Feb 20, 2026 at 12:03:17PM +0000, Maciej W. Rozycki wrote:
> On Thu, 19 Feb 2026, Bjorn Helgaas wrote:
> 
> > > Can we reconsider my patch that restricts the link retrain mechanism
> > > to the specific device that created the work-around?
> > > https://lore.kernel.org/all/20250702052430.13716-1-mattc@xxxxxxxxxxxxxxx/
> > 
> > I think we already at least potentially meddle with the link on every
> > device, and it definitely makes me nervous.  I would like it much
> > better if it's possible to limit it to devices with known defects.
> > 
> > I'll defer these for now and we can see if a consensus emerges.
> 
> As I say it's logically impossible to figure out whether or not to
> apply such a workaround where the culprit is the downstream device,
> because until you've succeeded establishing a link you have no way
> to figure out what the downstream device actually is.

IIUC Matthew [1] and Alok [2] have reported issues that only happen
when we run pcie_failed_link_retrain().  The issues seem to be with
NVMe devices, but I don't see a root cause or a solution (other than
skipping pcie_failed_link_retrain()).

[1] https://lore.kernel.org/all/20250702052430.13716-2-mattc@xxxxxxxxxxxxxxx/
[2] https://lore.kernel.org/all/c296df33-f9c0-42f7-8add-6966d89d00c4@xxxxxxxxxx/