On Tue, May 22, 2012 at 8:31 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> On Tue, May 22, 2012 at 7:43 PM, Jason Baron <jbaron@xxxxxxxxxx> wrote:
>> On Tue, May 22, 2012 at 02:21:13PM -0700, Yinghai Lu wrote:
>>> On Tue, May 22, 2012 at 1:11 PM, Jason Baron <jbaron@xxxxxxxxxx> wrote:
>>> > I'm tyring to support bridge hotplug and devices below it in qemu via acpi
>>> > hotplug. Currently only 1 level or 32 slots are supported. By allowing for a
>>> > second level, we will be able to support 32^2 devices.
>>> >
>>> > If I first hotplug the bridge with no devices intially below it, the hotplug
>>> > code sets the bridge memory window to 0 and does not increase it when
>>> > subsequent devices are added below it.
>>> >
>>> > Fix this, by calling pci_rescan_bus_bridge_resize(), on the bridge directly
>>> > below the root to re-size all the birdge windows that may have changed.
>>> >
>>> > Signed-off-by: Jason Baron <jbaron@xxxxxxxxxx>
>>> > ---
>>> > drivers/pci/hotplug/acpiphp_glue.c | 8 ++++++++
>>> > 1 files changed, 8 insertions(+), 0 deletions(-)
>>> >
>>> > diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
>>> > index 806c44f..8960c1e 100644
>>> > --- a/drivers/pci/hotplug/acpiphp_glue.c
>>> > +++ b/drivers/pci/hotplug/acpiphp_glue.c
>>> > @@ -792,6 +792,7 @@ static int __ref enable_device(struct acpiphp_slot *slot)
>>> > {
>>> > struct pci_dev *dev;
>>> > struct pci_bus *bus = slot->bridge->pci_bus;
>>> > + struct pci_bus *rescan_bus;
>>> > struct acpiphp_func *func;
>>> > int retval = 0;
>>> > int num, max, pass;
>>> > @@ -821,6 +822,13 @@ static int __ref enable_device(struct acpiphp_slot *slot)
>>> > }
>>> > }
>>> >
>>> > + /* Ensure we rescan/setup a bridge for new devs hanging off of it */
>>> > + rescan_bus = bus;
>>> > + while (rescan_bus->parent && rescan_bus->parent->self)
>>> > + rescan_bus = rescan_bus->parent;
>>> > + if (rescan_bus->self)
>>> > + pci_rescan_bus_bridge_resize(rescan_bus->self);
>>> > +
>>>
>>> No, you can not do that. some parents bus could have other devices
>>> and driver could be loaded for those devices.
>>> so can not release resources that are used by those devices to resize
>>> parent bridges.
>>>
>>
>> hmmm...this patch also does what I want:
>>
>>
>> diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
>> index 806c44f..be63c72 100644
>> --- a/drivers/pci/hotplug/acpiphp_glue.c
>> +++ b/drivers/pci/hotplug/acpiphp_glue.c
>> @@ -821,6 +821,10 @@ static int __ref enable_device(struct acpiphp_slot *slot)
>> }
>> }
>>
>> + /* Ensure we rescan/setup a bridge for new devs hanging off of it */
>> + if (bus->self)
>> + pci_assign_unassigned_bridge_resources(bus->self);
>> +
>> list_for_each_entry(func, &slot->funcs, sibling)
>> acpiphp_bus_add(func);
>>
>>
>> There appears to be a precedant for something very similar in:
>> drivers/pci/hotplug/pciehp_pci.c:pciehp_configure_device(), where there
>> is a call to 'pci_assign_unassigned_bridge_resources(), when a new
>> device is added...
>
> the bus could have other devices under that bridge already.
>
> so pci_assign_unassigned_bridge_resources() will still try to release
> the bridge resource and
> those devices resources.
>
> but pciehp we could do that, because it will only have one device
> under that pcie root port or downstream port.
>
> so you can make qemu to support pcie and pciehp.
>
> for hot add one hotplug bridge support, we have
> bus->self->is_hotplug_bridge to set, so it will have allocate
> minimum resource.
>
> so you also could try to use quirk etc to get that bit set.
> please check
> drivers/pci/quirks.c::
> /* Allow manual resource allocation for PCI hotplug bridges
> * via pci=hpmemsize=nnM and pci=hpiosize=nnM parameters. For
> * some PCI-PCI hotplug bridges, like PLX 6254 (former HINT HB6),
> * kernel fails to allocate resources when hotplug device is
> * inserted and PCI bus is rescanned.
> */
> static void __devinit quirk_hotplug_bridge(struct pci_dev *dev)
> {
> dev->is_hotplug_bridge = 1;
> }
>
> DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_HINT, 0x0020, quirk_hotplug_bridge);
>
> but still would prefer you to make qemu to support pciehp.
another solution could be:
in qemu acpi dsdt, you could set bridge size for new added bridge.
current pbus_size_mem() will not shrink the old bridge resource size.
Thanks
Yinghai Lu
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