On Fri, Dec 6, 2013 at 1:22 PM, Yinghai Lu <[email protected]> wrote: > During hotplug test on platform, found slot status register does not > report present status correctly. That present bit does not get cleared > even after that card is removed. > > That problem is caused by commit: > | commit 2debd9289997fc5d1c0043b41201a8b40d5e11d0 > | > | PCI: pciehp: Disable/enable link during slot power off/on > > It looks like chipset bug, that PresDet bit is "OR" operation between > sideband input from FPGA, and chipset inband detection from pcie link.
This doesn't sound like a chipset bug. It sounds like exactly what the spec describes: "Presence Detect State – This bit indicates the presence of an adapter in the slot, reflected by the logical “OR” of the Physical Layer in-band presence detect mechanism and, if present, any out-of-band presence detect mechanism defined for the slot’s corresponding form factor" (PCIe 3.0, sec 7.8.11). So I want to fix this pciehp problem, but between 2debd9289997 and this patch, pciehp_power_off_slot() is accumulating warts that make it look like we're just reacting to things that break rather than making a robust design to start with. > It does not like if we disable pcie link at first and power off > other side device, and it has input from inband detection > always 1. > > Workaround: Try turn on link a while after power off. > > After this patch, PresDet report correct status when removing or adding > card later. > > Signed-off-by: Yinghai Lu <[email protected]> > Cc: Kenji Kaneshige <[email protected]> > Cc: <[email protected]> 3.4+ > > --- > drivers/pci/hotplug/pciehp_hpc.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > Index: linux-2.6/drivers/pci/hotplug/pciehp_hpc.c > =================================================================== > --- linux-2.6.orig/drivers/pci/hotplug/pciehp_hpc.c > +++ linux-2.6/drivers/pci/hotplug/pciehp_hpc.c > @@ -637,6 +637,15 @@ int pciehp_power_off_slot(struct slot * > } > ctrl_dbg(ctrl, "%s: SLOTCTRL %x write cmd %x\n", __func__, > pci_pcie_cap(ctrl->pcie->port) + PCI_EXP_SLTCTL, slot_cmd); > + > + /* > + * Enable link for a while so chipset could settle down > + * inband presence detection logic > + */ > + pciehp_link_enable(ctrl); > + msleep(20); > + pciehp_link_disable(ctrl); > + > return 0; > } > -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
