On 09/25/2012 06:10 AM, Bjorn Helgaas wrote: > On Wed, Aug 22, 2012 at 9:16 AM, Jiang Liu <liuj97@xxxxxxxxx> wrote: >> From: Jiang Liu <jiang.liu@xxxxxxxxxx> >> >> Commit 0d52f54e2ef64c189dedc332e680b2eb4a34590a (PCI / ACPI: Make acpiphp >> ignore root bridges using PCIe native hotplug) added code that made the >> acpiphp driver completely ignore PCIe root complexes for which the kernel >> had been granted control of the native PCIe hotplug feature by the BIOS >> through _OSC. Later commit 619a5182d1f38a3d629ee48e04fa182ef9170052 >> "PCI hotplug: Always allow acpiphp to handle non-PCIe bridges" relaxed >> the constraints to allow acpiphp driver handle non-PCIe bridges under >> such a complex. The constraint needs to be relaxed further to allow >> acpiphp driver to hanlde PCIe ports without native PCIe hotplug capability. >> >> Some MR-IOV switch chipsets, such PLX8696, support multiple virtual PCIe >> switches and may migrate downstream ports among virtual switches. >> To migrate a downstream port from the source virtual switch to the target, >> the port needs to be hot-removed from the source and hot-added into the >> target. pciehp driver can't be used here because there's no slots within >> the virtual PCIe switch. So acpiphp driver is used to support downstream >> port migration. A typical configuration is as below: >> [Root w/o native PCIe HP] >> [Upstream port of vswitch w/o native PCIe HP] >> [Downstream port of vswitch w/ native PCIe HP] >> [PCIe enpoint] >> >> Here acpiphp driver will be used to handle root ports and upstream port >> in the virtual switch, and pciehp driver will be used to handle downstream >> ports in the virtual switch. >> >> v1->v2: use PCIe capability accessors to read PCI_EXP_SLTCAP register >> >> Acked-by: Rafael J. Wysocki <rjw@xxxxxxx> >> Signed-off-by: Jiang Liu <liuj97@xxxxxxxxx> > > I tweaked the changelog (typos, indentation) and applied this to my > "pci/jiang-acpiphp" branch. Kenji acked a previous version, but I > didn't add it here because this is slightly updated. > > If the PLX8696 supports moving downstream ports between upstream > ports, it seems like a deficiency if the upstream port doesn't support > native hotplug. If I understand correctly, this patch allows the use > of acpiphp for "hotplug" of the downstream ports, but that is only an > option if the PLX8696 is in the ACPI namespace. > > It seems like the lack of PLX8696 native hotplug for upstream ports > mean this virtual switch migration can only be done if the PLX8696 is > soldered into the system -- for instance, we don't have any way to > deal with an 8696 on a plug-in card because ACPI won't know anything > about that device. Hi Bjorn, That's true, we can't deal with 8696 on add-in cards yet. The platform we are working with is: The motherboard has a specially designed slot for a root port, which could only be used to connect an IO-extension box with 8696. So the BIOS could build ACPI objects for the 8696 chipset. Thanks! Gerry -- 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
