Hello, > -----Original Message----- > From: linux-pci-owner@xxxxxxxxxxxxxxx [mailto:linux-pci- > owner@xxxxxxxxxxxxxxx] On Behalf Of Bjorn Helgaas > Sent: Saturday, December 07, 2013 10:36 AM > To: Yinghai Lu > Cc: linux-pci@xxxxxxxxxxxxxxx; Kenji Kaneshige; stable@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] PCI, pciehp: Turn on link a while to workaround > presense detection > > On Fri, Dec 6, 2013 at 1:22 PM, Yinghai Lu <yinghai@xxxxxxxxxx> 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. Yes. In fact things do get more complicated if we introduce link state based hot-plug, because then that requires that we do NOT disable the link permanently during power off. (Because we would want to receive future hot-plug link-up events). > > > 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 <yinghai@xxxxxxxxxx> > > Cc: Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx> > > Cc: <stable@xxxxxxxxxxxxxxx> 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 linux-pci" in > the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info > at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
