> However, hardware could have already set LBMS when the device was > connected to the port i.e when the state was DL_Up or DL_Active. Some > hardwares would have even attempted retrain going into recovery mode, > just before transitioning to DL_Down. > > Thus the set LBMS is never cleared and might force software to cause link > speed drops when there is no link [2]. > > Dmesg before: > pcieport 0000:20:01.1: pciehp: Slot(59): Link Down > pcieport 0000:20:01.1: pciehp: Slot(59): Card present > pcieport 0000:20:01.1: broken device, retraining non-functional downstream link at 2.5GT/s > pcieport 0000:20:01.1: retraining failed > pcieport 0000:20:01.1: pciehp: Slot(59): No link > > Dmesg after: > pcieport 0000:20:01.1: pciehp: Slot(59): Link Down > pcieport 0000:20:01.1: pciehp: Slot(59): Card present > pcieport 0000:20:01.1: pciehp: Slot(59): No link I'm a little confused about the problem being solved here. Obviously the message is extraneous. I guess the slot is empty, so retraining is meaningless and will always fail. Maybe avoiding it avoids a delay? Is the benefit that we get rid of the message and a delay? > [1] PCI Express Base Specification Revision 6.2, Jan 25 2024. > https://members.pcisig.com/wg/PCI-SIG/document/20590 > [2] Commit a89c82249c37 ("PCI: Work around PCIe link training failures") > > Fixes: a89c82249c37 ("PCI: Work around PCIe link training failures") Lukas asked about this; did you confirm that it is related? Asking because the Fixes tag may cause this to be backported along with a89c82249c37. > Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@xxxxxxx> > --- > Link to v1: > https://lore.kernel.org/all/20240424033339.250385-1-Smita.KoralahalliChannabasappa@xxxxxxx/ > > v2: > Cleared LBMS unconditionally. (Ilpo) > Added Fixes Tag. (Lukas) > --- > drivers/pci/hotplug/pciehp_pci.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/pci/hotplug/pciehp_pci.c b/drivers/pci/hotplug/pciehp_pci.c > index ad12515a4a12..dae73a8932ef 100644 > --- a/drivers/pci/hotplug/pciehp_pci.c > +++ b/drivers/pci/hotplug/pciehp_pci.c > @@ -134,4 +134,7 @@ void pciehp_unconfigure_device(struct controller *ctrl, bool presence) > } > > pci_unlock_rescan_remove(); > + > + pcie_capability_write_word(ctrl->pcie->port, PCI_EXP_LNKSTA, > + PCI_EXP_LNKSTA_LBMS); > } > -- > 2.17.1 >
