PCI: Allocate 64-bit BARs above 4G when possible

Try to allocate space for 64-bit BARs above 4G first, to preserve the space
below 4G for 32-bit BARs.  If there's no space above 4G available, fall
back to allocating anywhere.

[bhelgaas: reworked starting from http://lkml.kernel.org/r/1387485843-17403-2-git-send-email-yinghai@kernel.org]
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index c30baae929f4..86fb8ec5e448 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -102,6 +102,8 @@ static struct pci_bus_region pci_32_bit = {0, 0xffffffffULL};
 #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
 static struct pci_bus_region pci_64_bit = {0,
                                 (dma_addr_t) 0xffffffffffffffffULL};
+static struct pci_bus_region pci_high = {(dma_addr_t) 0x100000000ULL,
+                                (dma_addr_t) 0xffffffffffffffffULL};
 #endif
 
 /*
@@ -198,8 +200,7 @@ static int pci_bus_alloc_from_region(struct pci_bus *bus, struct resource *res,
  * alignment and type, try to find an acceptable resource allocation
  * for a specific device resource.
  */
-int
-pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
+int pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
                 resource_size_t size, resource_size_t align,
                 resource_size_t min, unsigned int type_mask,
                 resource_size_t (*alignf)(void *,
@@ -209,10 +210,19 @@ pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
                 void *alignf_data)
 {
 #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
-        if (res->flags & IORESOURCE_MEM_64)
+        int rc;
+
+        if (res->flags & IORESOURCE_MEM_64) {
+                rc = pci_bus_alloc_from_region(bus, res, size, align, min,
+                                               type_mask, alignf, alignf_data,
+                                               &pci_high);
+                if (rc == 0)
+                        return 0;
+
                 return pci_bus_alloc_from_region(bus, res, size, align, min,
                                                  type_mask, alignf, alignf_data,
                                                  &pci_64_bit);
+        }
 #endif
 
         return pci_bus_alloc_from_region(bus, res, size, align, min,