From: Yinghai Lu <yinghai@kernel.org>

The powerpc-specific __pci_mmap_set_pgprot() does two things:

  1) Disables write combining for I/O port space mappings

     This only affects procfs mappings.  The pci_mmap_resource() sysfs path
     only requests write combining for resources with IORESOURCE_PREFETCH
     set, which doesn't include I/O resources.

     The only way to request write combining for I/O port space mappings
     was via the PCIIOC_WRITE_COMBINE ioctl and the proc_bus_pci_mmap()
     path, and we recently changed that path to ignore write combining for
     I/O, so this code in powerpc is no longer needed.

  2) Automatically enables write combining for mappings of prefetchable
     resources, even if not requested by the user

     Both procfs (via PCIIOC_MMAP_IS_MEM and PCIIOC_WRITE_COMBINE ioctls)
     and sysfs (via "resourceN_wc" files, which are created for resources
     with IORESOURCE_PREFETCH) provide ways for the user to map PCI memory
     space with write combining.

     Users that desire write combining should use one of those ways instead
     of relying on powerpc-specific behavior.

Remove the powerpc-specific __pci_mmap_set_pgprot().

The user-visible effect of this change is that users mapping prefetchable
PCI memory space via procfs without PCIIOC_WRITE_COMBINE or via sysfs
"resourceN" (not "resourceN_wc") will get regular uncacheable mappings
instead of the write combining mappings they used to get.

The new behavior matches the behavior on all other arches that support
write combining mapping.

[bhelgaas: changelog]
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
 arch/powerpc/kernel/pci-common.c |   37 ++++---------------------------------
 1 file changed, 4 insertions(+), 33 deletions(-)

diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index 0f7a60f..8c6beb0 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c

@@ -356,36 +356,6 @@ static struct resource *__pci_mmap_make_offset(struct pci_dev *dev,
 }
 
 /*
- * Set vm_page_prot of VMA, as appropriate for this architecture, for a pci
- * device mapping.
- */
-static pgprot_t __pci_mmap_set_pgprot(struct pci_dev *dev, struct resource *rp,
-				      pgprot_t protection,
-				      enum pci_mmap_state mmap_state,
-				      int write_combine)
-{
-
-	/* Write combine is always 0 on non-memory space mappings. On
-	 * memory space, if the user didn't pass 1, we check for a
-	 * "prefetchable" resource. This is a bit hackish, but we use
-	 * this to workaround the inability of /sysfs to provide a write
-	 * combine bit
-	 */
-	if (mmap_state != pci_mmap_mem)
-		write_combine = 0;
-	else if (write_combine == 0) {
-		if (rp->flags & IORESOURCE_PREFETCH)
-			write_combine = 1;
-	}
-
-	/* XXX would be nice to have a way to ask for write-through */
-	if (write_combine)
-		return pgprot_noncached_wc(protection);
-	else
-		return pgprot_noncached(protection);
-}
-
-/*
  * This one is used by /dev/mem and fbdev who have no clue about the
  * PCI device, it tries to find the PCI device first and calls the
  * above routine

@@ -458,9 +428,10 @@ int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
 		return -EINVAL;
 
 	vma->vm_pgoff = offset >> PAGE_SHIFT;
-	vma->vm_page_prot = __pci_mmap_set_pgprot(dev, rp,
-						  vma->vm_page_prot,
-						  mmap_state, write_combine);
+	if (write_combine)
+		vma->vm_page_prot = pgprot_noncached_wc(vma->vm_page_prot);
+	else
+		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 
 	ret = remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
 			       vma->vm_end - vma->vm_start, vma->vm_page_prot);