[+cc Yinghai] On Wed, Jan 8, 2014 at 11:17 AM, threeTigers Lin <threeflytigers@xxxxxxxxx> wrote: > From f7a37ed1c61b5939ccef810e28b25ecf3bfa9077 Mon Sep 17 00:00:00 2001 > From: linmuhui <linmuhui@xxxxxxxxxx> > Date: Thu, 9 Jan 2014 01:03:12 +0800 > Subject: [PATCH] PCI: Allocate prefetch mmio resource first when possible This patch is not in the standard format and does not apply cleanly. See Documentation/SubmittingPatches. > Hi Bjorn, > > PCI bus resources will be set up at pci_bridge_check_ranges() or > pci_read_bridge_bases(). In both cases, we can find that the PCI bus' > non-pref mmio will be assigned to bus->resource[1] and pref mmio will be > assigned to bus->resource[2]. So, in the scenario that we need to allocate > pref resources from PCI bus such as hotplug operation, the bus' non-pref > mmio will be quickly eaten up first if we try to allocate bus resources in > the order from bus->resource[0] to bus->resource[PCI_BRIDGE_RESOURCE_NUM - > 1] in the function pci_bus_alloc_resource(), even though there is enough > pref mmio resource of the bus. This may lead to the later requester who want > to allocate non-pref mmio cannot allocate the resource from the bus. So, I > think the order of allocating PCI bus resources in function > pci_bus_alloc_resource() should be changed to try pref mmio first when > possible. Don't we do this already? The code in __pci_assign_resource() looks like it should prefer an exact prefetching match. If that code doesn't work, we should fix it there. I don't want to fiddle with pci_bus_for_each_resource() for this -- that's a really arcane place to hide such a fix. Bjorn > Signed-off-by: Lin Muhui <linmuhui@xxxxxxxxxx> > --- > include/linux/pci.h | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 1084a15..238df8f 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -1064,7 +1064,8 @@ void pci_bus_remove_resources(struct pci_bus *bus); > > #define pci_bus_for_each_resource(bus, res, i) \ > for (i = 0; \ > - (res = pci_bus_resource_n(bus, i)) || i < > PCI_BRIDGE_RESOURCE_NUM; \ > + (res = pci_bus_resource_n(bus, (i < PCI_BRIDGE_RESOURCE_NUM ? > (PCI_BRIDGE_RESOURCE_NUM - 1 - i) : i)))\ > + || i < PCI_BRIDGE_RESOURCE_NUM; \ > i++) > > int __must_check pci_bus_alloc_resource(struct pci_bus *bus, > -- > 1.7.1 > -- 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
