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authorBjorn Helgaas <bhelgaas@google.com>2016-06-08 22:46:54 +0300
committerBjorn Helgaas <bhelgaas@google.com>2016-06-17 22:43:33 +0300
commit3a92c319c44a7bcee9f48dff9d97d001943b54c6 (patch)
treeb9bee26ae26404cc873d2d24817981ff77ffc449 /drivers/pci/proc.c
parentaf8c34ce6ae32addda3788d54a7e340cad22516b (diff)
downloadlinux-3a92c319c44a7bcee9f48dff9d97d001943b54c6.tar.xz
PCI: Ignore write combining when mapping I/O port space
PCI exposes files like /proc/bus/pci/00/00.0 in procfs. These files support operations like this: ioctl(fd, PCIIOC_MMAP_IS_IO); # request I/O port space ioctl(fd, PCIIOC_WRITE_COMBINE, 1); # request write-combining mmap(fd, ...) Write combining is useful on PCI memory space, but I don't think it makes sense on PCI I/O port space. We *could* change proc_bus_pci_ioctl() to make it impossible to set mmap_state == pci_mmap_io and write_combine at the same time, but that would break the following sequence, which is currently legal: mmap(fd, ...) # default is I/O, non-combining ioctl(fd, PCIIOC_WRITE_COMBINE, 1); # request write-combining ioctl(fd, PCIIOC_MMAP_IS_MEM); # request memory space mmap(fd, ...) # get write-combining mapping Ignore the write-combining flag when mapping I/O port space. This patch should have no functional effect, based on this analysis of all implementations of pci_mmap_page_range(): - ia64 mips parisc sh unicore32 x86 do not support mapping of I/O port space at all. - arm cris microblaze mn10300 sparc xtensa support mapping of I/O port space, but ignore the write_combine argument to pci_mmap_page_range(). - powerpc supports mapping of I/O port space and uses write_combine, and it disables write combining for I/O port space in __pci_mmap_set_pgprot(). This patch makes it possible to remove __pci_mmap_set_pgprot() from powerpc, which simplifies that path. Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'drivers/pci/proc.c')
-rw-r--r--drivers/pci/proc.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index 3f155e78513f..2408abe4ee8c 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -231,7 +231,7 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
{
struct pci_dev *dev = PDE_DATA(file_inode(file));
struct pci_filp_private *fpriv = file->private_data;
- int i, ret;
+ int i, ret, write_combine;
if (!capable(CAP_SYS_RAWIO))
return -EPERM;
@@ -245,9 +245,12 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
if (i >= PCI_ROM_RESOURCE)
return -ENODEV;
+ if (fpriv->mmap_state == pci_mmap_mem)
+ write_combine = fpriv->write_combine;
+ else
+ write_combine = 0;
ret = pci_mmap_page_range(dev, vma,
- fpriv->mmap_state,
- fpriv->write_combine);
+ fpriv->mmap_state, write_combine);
if (ret < 0)
return ret;