From: Yinghai Lu <yinghai@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
---
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);
--
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