PCI: Support 64-bit bridge windows if we have 64-bit dma_addr_t

Aaron reported that a 32-bit x86 kernel with Physical Address Extension
(PAE) support complains about bridge prefetchable memory windows above 4GB:

  pci_bus 0000:00: root bus resource [mem 0x380000000000-0x383fffffffff]
  ...
  pci 0000:03:00.0: reg 0x10: [mem 0x383fffc00000-0x383fffdfffff 64bit pref]
  pci 0000:03:00.0: reg 0x20: [mem 0x383fffe04000-0x383fffe07fff 64bit pref]
  pci 0000:03:00.1: reg 0x10: [mem 0x383fffa00000-0x383fffbfffff 64bit pref]
  pci 0000:03:00.1: reg 0x20: [mem 0x383fffe00000-0x383fffe03fff 64bit pref]
  pci 0000:00:02.2: PCI bridge to [bus 03-04]
  pci 0000:00:02.2:   bridge window [io  0x1000-0x1fff]
  pci 0000:00:02.2:   bridge window [mem 0x91900000-0x91cfffff]
  pci 0000:00:02.2: can't handle 64-bit address space for bridge

In this kernel, unsigned long is 32 bits and dma_addr_t is 64 bits.
Previously we used "unsigned long" to hold the bridge window address.  But
this is a bus address, so we should use dma_addr_t instead.

Use dma_addr_t to hold the bridge window base and limit.

The question of whether the CPU can actually *address* the window is
separate and depends on what the physical address space of the CPU is and
whether the host bridge does any address translation.

[bhelgaas: fix "shift count > width of type", changelog, stable tag]
Fixes: d56dbf5bab8c ("PCI: Allocate 64-bit BARs above 4G when possible")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=88131
Reported-by: Aaron Ma <mapengyu@gmail.com>
Tested-by: Aaron Ma <mapengyu@gmail.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v3.14+

drivers/pci/probe.c

@@ -407,15 +407,16 @@ static void pci_read_bridge_mmio_pref(struct pci_bus *child)
 {
 	struct pci_dev *dev = child->self;
 	u16 mem_base_lo, mem_limit_lo;
-	unsigned long base, limit;
+	u64 base64, limit64;
+	dma_addr_t base, limit;
 	struct pci_bus_region region;
 	struct resource *res;
 
 	res = child->resource[2];
 	pci_read_config_word(dev, PCI_PREF_MEMORY_BASE, &mem_base_lo);
 	pci_read_config_word(dev, PCI_PREF_MEMORY_LIMIT, &mem_limit_lo);
-	base = ((unsigned long) mem_base_lo & PCI_PREF_RANGE_MASK) << 16;
-	limit = ((unsigned long) mem_limit_lo & PCI_PREF_RANGE_MASK) << 16;
+	base64 = (mem_base_lo & PCI_PREF_RANGE_MASK) << 16;
+	limit64 = (mem_limit_lo & PCI_PREF_RANGE_MASK) << 16;
 
 	if ((mem_base_lo & PCI_PREF_RANGE_TYPE_MASK) == PCI_PREF_RANGE_TYPE_64) {
 		u32 mem_base_hi, mem_limit_hi;
@@ -429,17 +430,20 @@ static void pci_read_bridge_mmio_pref(struct pci_bus *child)
 		 * this, just assume they are not being used.
 		 */
 		if (mem_base_hi <= mem_limit_hi) {
-#if BITS_PER_LONG == 64
-			base |= ((unsigned long) mem_base_hi) << 32;
-			limit |= ((unsigned long) mem_limit_hi) << 32;
-#else
-			if (mem_base_hi || mem_limit_hi) {
-				dev_err(&dev->dev, "can't handle 64-bit address space for bridge\n");
-				return;
-			}
-#endif
+			base64 |= (u64) mem_base_hi << 32;
+			limit64 |= (u64) mem_limit_hi << 32;
 		}
 	}
+
+	base = (dma_addr_t) base64;
+	limit = (dma_addr_t) limit64;
+
+	if (base != base64) {
+		dev_err(&dev->dev, "can't handle bridge window above 4GB (bus address %#010llx)\n",
+			(unsigned long long) base64);
+		return;
+	}
+
 	if (base <= limit) {
 		res->flags = (mem_base_lo & PCI_PREF_RANGE_TYPE_MASK) |
 					 IORESOURCE_MEM | IORESOURCE_PREFETCH;