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powerpc/pci: Remove __pci_mmap_set_pgprot() 

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 powerpc 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>
This commit is contained in:
Yinghai Lu 2016-06-17 14:43:33 -05:00 committed by Bjorn Helgaas
parent 3a92c319c4
commit 1e70cdd6e6
1 changed files with 4 additions and 33 deletions
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37
arch/powerpc/kernel/pci-common.c
View File

@ -355,36 +355,6 @@ static struct resource *__pci_mmap_make_offset(struct pci_dev *dev,
return NULL;
}
/*
* 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
@ -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);