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PCI: Add arch_can_pci_mmap_wc() macro

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Most of the almost-identical versions of pci_mmap_page_range() silently
ignore the 'write_combine' argument and give uncached mappings.

Yet we allow the PCIIOC_WRITE_COMBINE ioctl in /proc/bus/pci, expose the
'resourceX_wc' file in sysfs, and allow an attempted mapping to apparently
succeed.

To fix this, introduce a macro arch_can_pci_mmap_wc() which indicates
whether the platform can do a write-combining mapping.  On x86 this ends up
being pat_enabled(), while the few other platforms that support it can just
set it to a literal '1'.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
David Woodhouse 2017-04-12 13:25:54 +01:00 • committed by Bjorn Helgaas
parent 03a064b431
commit ae749c7ab4
7 changed files with 25 additions and 11 deletions
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2
arch/ia64/include/asm/pci.h
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@ -51,6 +51,8 @@ extern unsigned long ia64_max_iommu_merge_mask;
#define PCI_DMA_BUS_IS_PHYS (ia64_max_iommu_merge_mask == ~0UL)
#define HAVE_PCI_MMAP
#define arch_can_pci_mmap_wc() 1
extern int pci_mmap_page_range (struct pci_dev *dev, struct vm_area_struct *vma,
enum pci_mmap_state mmap_state, int write_combine);
#define HAVE_PCI_LEGACY