Re: [PATCH] pci: pciehp update the slot bridge res to get big rangefor pcie devices

[Kenji Kaneshige]

Yinghai Lu wrote:
> Kenji Kaneshige wrote:
> > Yinghai Lu wrote:
> > > move out bus_size_bridges and assign resources out of pciehp_add_bridge()
> > > and at last do them all together one time including slot bridge, to
> > > avoid to call
> > > assign resources several times, when there are several bridges under
> > > the slot bridge.
> > >
> > > need to introduce pci_bridge_assign_resources there.
> > >
> > > handle the case the first bridge that doesn't get pre-allocated big
> > > enough res from FW.
> > > for example pcie devices need 256M, but the bridge only get
> > > preallocated 2M...
> > Though I have not looked at the patch deeply yet (sorry), I have
> > some questions and concerns about this change. Please correct me
> > if my understanding is not correct.
> >
> > - Your patch doesn't seems to have the code to free resources.
> >  If we need to expand the resource range, don't we need to free
> >  preallocated resource before allocating the new one?
>
> that is done with pci_bus_size_bridges ==> pbus_size_io/pbus_size_mem ==> find_free_bus_resource ==> release_resource.

I didn't noticed that find_free_bus_resource() was changed to call
release_resource() recently...

By the way, does this (release_resource() by find_bus_resource())
change the resource assignment by BIOS also for bridges other than
the ports with hotplug slot (switch upstreamport, for example)?

> > - Your patch seems to update BARs for bridge itself. I think it
> >  would break the bridge's driver (port service driver) that if
> >  it controls the device's capability by using IO/Mem, though I
> >  don't know if such driver or capabilities exists now.
>
> port service driver will be AER and pciehotplug.
> it seems those driver are not use those BAR...
> those BAR are supposed for the devices under the pcie bridge.

I understand that there are only two port service drivers (AER and
PCIe hotplug) and both doesn't use BAR. But I still have a concern
that changing bridge's BARs might cause problems in the future. In
my understanding, what you need is expanding IO/Mem base and limit
of root or switch downstream ports. If so, I think we should only
touch IO/Mem base/limit, and should not touch bridge's BARs.

Thanks,
Kenji Kaneshige

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