Hi Bjorn,
You still seem to have the old version of this patch in enumeration
branch.
Could you please consider replacing it with this v3 one that is slightly
better (use_lt was changed to true because it makes more sense).
On Mon, 26 Aug 2024, Ilpo Järvinen wrote:
> On Sun, 25 Aug 2024, Maciej W. Rozycki wrote:
>
> > When `pcie_failed_link_retrain' has failed to retrain the link by hand
> > it leaves the link speed restricted to 2.5GT/s, which will then affect
> > any device that has been plugged in later on, which may not suffer from
> > the problem that caused the speed restriction to have been attempted.
> > Consequently such a downstream device will suffer from an unnecessary
> > communication throughput limitation and therefore performance loss.
> >
> > Remove the speed restriction then and revert the Link Control 2 register
> > to its original state if link retraining with the speed restriction in
> > place has failed. Retrain the link again afterwards so as to remove any
> > residual state, waiting on LT rather than DLLLA to avoid an excessive
> > delay and ignoring the result as this training is supposed to fail anyway.
> >
> > Fixes: a89c82249c37 ("PCI: Work around PCIe link training failures")
> > Reported-by: Matthew W Carlis <mattc@xxxxxxxxxxxxxxx>
> > Link: https://lore.kernel.org/r/20240806000659.30859-1-mattc@xxxxxxxxxxxxxxx/
> > Link: https://lore.kernel.org/r/20240722193407.23255-1-mattc@xxxxxxxxxxxxxxx/
> > Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx # v6.5+
> > ---
> > Changes from v2:
> >
> > - Wait on LT rather than DLLLA with clean-up retraining with the speed
> > restriction lifted, so as to avoid an excessive delay as it's supposed
> > to fail anyway.
> >
> > New change in v2.
> > ---
> > drivers/pci/quirks.c | 11 ++++++++++-
> > 1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > linux-pcie-failed-link-retrain-fail-unclamp.diff
> > Index: linux-macro/drivers/pci/quirks.c
> > ===================================================================
> > --- linux-macro.orig/drivers/pci/quirks.c
> > +++ linux-macro/drivers/pci/quirks.c
> > @@ -66,7 +66,7 @@
> > * apply this erratum workaround to any downstream ports as long as they
> > * support Link Active reporting and have the Link Control 2 register.
> > * Restrict the speed to 2.5GT/s then with the Target Link Speed field,
> > - * request a retrain and wait 200ms for the data link to go up.
> > + * request a retrain and check the result.
> > *
> > * If this turns out successful and we know by the Vendor:Device ID it is
> > * safe to do so, then lift the restriction, letting the devices negotiate
> > @@ -74,6 +74,10 @@
> > * firmware may have already arranged and lift it with ports that already
> > * report their data link being up.
> > *
> > + * Otherwise revert the speed to the original setting and request a retrain
> > + * again to remove any residual state, ignoring the result as it's supposed
> > + * to fail anyway.
> > + *
> > * Return TRUE if the link has been successfully retrained, otherwise FALSE.
> > */
> > bool pcie_failed_link_retrain(struct pci_dev *dev)
> > @@ -92,6 +96,8 @@ bool pcie_failed_link_retrain(struct pci
> > pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta);
> > if ((lnksta & (PCI_EXP_LNKSTA_LBMS | PCI_EXP_LNKSTA_DLLLA)) ==
> > PCI_EXP_LNKSTA_LBMS) {
> > + u16 oldlnkctl2 = lnkctl2;
> > +
> > pci_info(dev, "broken device, retraining non-functional downstream link at 2.5GT/s\n");
> >
> > lnkctl2 &= ~PCI_EXP_LNKCTL2_TLS;
> > @@ -100,6 +106,9 @@ bool pcie_failed_link_retrain(struct pci
> >
> > if (pcie_retrain_link(dev, false)) {
> > pci_info(dev, "retraining failed\n");
> > + pcie_capability_write_word(dev, PCI_EXP_LNKCTL2,
> > + oldlnkctl2);
> > + pcie_retrain_link(dev, true);
>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
--
i.
