Re: [PATCH v12 01/15] PCI: Let pci_mmap_page_range() take extra resource pointer

commit 4e712b691abc5b579e3e4327f56b0b7988bdd1cb
Author: Bjorn Helgaas [off-list ref]
Date:   Wed Jun 8 14:00:14 2016 -0500

    microblaze/PCI: Remove useless __pci_mmap_set_pgprot()

    The microblaze __pci_mmap_set_pgprot() was apparently copied from powerpc,
    where it computes either an uncacheable pgprot_t or a write-combining one.
    But on microblaze, we always use the regular uncacheable pgprot_t.

    Remove the useless code in __pci_mmap_set_pgprot() and inline the
    pgprot_noncached() at the only caller.

    Signed-off-by: Bjorn Helgaas [off-list ref]

diff --git a/arch/microblaze/pci/pci-common.c b/arch/microblaze/pci/pci-common.c
index 14cba60..1974567 100644
--- a/arch/microblaze/pci/pci-common.c
+++ b/arch/microblaze/pci/pci-common.c

@@ -219,33 +219,6 @@ 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)
-{
-       pgprot_t prot = protection;
-
-       /* 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;
-       }
-
-       return pgprot_noncached(prot);
-}
-
-/*
  * 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

@@ -317,9 +290,7 @@ 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);
+       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);

commit 962972ee5e0ba6ceb680cb182bad65f8886586a6
Author: Bjorn Helgaas [off-list ref]
Date:   Wed Jun 8 14:46:54 2016 -0500

    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, ...)

    Many architectures don't allow mmap of I/O port space at all, but I don't
    think it makes sense to do a write-combining mapping on the ones that do.
    We could change proc_bus_pci_ioctl() so the user could never enable write-
    combining for I/O port space, 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, ...)

    Ignore the write-combining flag when mapping I/O port space.

    Signed-off-by: Bjorn Helgaas [off-list ref]

diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index 3f155e7..21f8d613 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c

@@ -247,7 +247,8 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)

        ret = pci_mmap_page_range(dev, vma,
                                  fpriv->mmap_state,
-                                 fpriv->write_combine);
+                                 (fpriv->mmap_state == pci_mmap_mem) ?
+                                       fpriv->write_combine : 0);
        if (ret < 0)
                return ret;