PCI: Remove pci_mmap_page_range() wrapper

The ARCH_GENERIC_PCI_MMAP_RESOURCE symbol came up in a recent discussion,
and I noticed that this was left behind by an unfinished cleanup from 2017.

The only architecture that still relies on providing its own
pci_mmap_page_range() helper instead of using the generic
pci_mmap_resource_range() is sparc. Presumably the reasons for this have
not changed, but at least this can be simplified by converting sparc to use
the same interface as the others.

The only difference between the two is the device-specific offset that gets
added to or subtracted from vma->vm_pgoff.

Change the only caller of pci_mmap_page_range() in common code to subtract
this offset and call the modern interface, while adding it back in the
sparc implementation to preserve the existing behavior.

This removes the complexities of the dual interfaces from the common code,
and keeps it all specific to the sparc architecture code. According to
David Miller, the sparc code lets user space poke into the VGA I/O port
registers by mmapping the I/O space of the parent bridge device, which is
something that the generic pci_mmap_resource_range() code apparently does
not.

Link: https://lore.kernel.org/lkml/1519887203.622.3.camel@infradead.org/t/
Link: https://lore.kernel.org/lkml/20220714214657.2402250-3-shorne@gmail.com/
Link: https://lore.kernel.org/r/20220715153617.3393420-1-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Stafford Horne <shorne@gmail.com>

Documentation/PCI/sysfs-pci.rst

@@ -125,7 +125,7 @@ implementation of that functionality. To support the historical interface of
 mmap() through files in /proc/bus/pci, platforms may also set HAVE_PCI_MMAP.
 
 Alternatively, platforms which set HAVE_PCI_MMAP may provide their own
-implementation of pci_mmap_page_range() instead of defining
+implementation of pci_mmap_resource_range() instead of defining
 ARCH_GENERIC_PCI_MMAP_RESOURCE.
 
 Platforms which support write-combining maps of PCI resources must define

arch/sparc/kernel/pci.c

@@ -876,17 +876,22 @@ static void __pci_mmap_set_pgprot(struct pci_dev *dev, struct vm_area_struct *vm
 
 /* Perform the actual remap of the pages for a PCI device mapping, as appropriate
  * for this architecture.  The region in the process to map is described by vm_start
- * and vm_end members of VMA, the base physical address is found in vm_pgoff.
+ * and vm_end members of VMA, the BAR relative address is found in vm_pgoff.
  * The pci device structure is provided so that architectures may make mapping
  * decisions on a per-device or per-bus basis.
  *
  * Returns a negative error code on failure, zero on success.
  */
-int pci_mmap_page_range(struct pci_dev *dev, int bar,
+int pci_mmap_resource_range(struct pci_dev *dev, int bar,
-			struct vm_area_struct *vma,
+			    struct vm_area_struct *vma,
-			enum pci_mmap_state mmap_state, int write_combine)
+			    enum pci_mmap_state mmap_state, int write_combine)
 {
 	int ret;
+	resource_size_t start, end;
+
+	/* convert per-BAR address to PCI bus address */
+	pci_resource_to_user(dev, bar, &dev->resource[bar], &start, &end);
+	vma->vm_pgoff += start >> PAGE_SHIFT;
 
 	ret = __pci_mmap_make_offset(dev, vma, mmap_state);
 	if (ret < 0)

drivers/pci/mmap.c

@@ -13,27 +13,6 @@
 
 #ifdef ARCH_GENERIC_PCI_MMAP_RESOURCE
 
-/*
- * Modern setup: generic pci_mmap_resource_range(), and implement the legacy
- * pci_mmap_page_range() (if needed) as a wrapper round it.
- */
-
-#ifdef HAVE_PCI_MMAP
-int pci_mmap_page_range(struct pci_dev *pdev, int bar,
-			struct vm_area_struct *vma,
-			enum pci_mmap_state mmap_state, int write_combine)
-{
-	resource_size_t start, end;
-
-	pci_resource_to_user(pdev, bar, &pdev->resource[bar], &start, &end);
-
-	/* Adjust vm_pgoff to be the offset within the resource */
-	vma->vm_pgoff -= start >> PAGE_SHIFT;
-	return pci_mmap_resource_range(pdev, bar, vma, mmap_state,
-				       write_combine);
-}
-#endif
-
 static const struct vm_operations_struct pci_phys_vm_ops = {
 #ifdef CONFIG_HAVE_IOREMAP_PROT
 	.access = generic_access_phys,
@@ -70,27 +49,4 @@ int pci_mmap_resource_range(struct pci_dev *pdev, int bar,
 				  vma->vm_page_prot);
 }
 
-#elif defined(HAVE_PCI_MMAP) /* && !ARCH_GENERIC_PCI_MMAP_RESOURCE */
-
-/*
- * Legacy setup: Implement pci_mmap_resource_range() as a wrapper around
- * the architecture's pci_mmap_page_range(), converting to "user visible"
- * addresses as necessary.
- */
-
-int pci_mmap_resource_range(struct pci_dev *pdev, int bar,
-			    struct vm_area_struct *vma,
-			    enum pci_mmap_state mmap_state, int write_combine)
-{
-	resource_size_t start, end;
-
-	/*
-	 * pci_mmap_page_range() expects the same kind of entry as coming
-	 * from /proc/bus/pci/ which is a "user visible" value. If this is
-	 * different from the resource itself, arch will do necessary fixup.
-	 */
-	pci_resource_to_user(pdev, bar, &pdev->resource[bar], &start, &end);
-	vma->vm_pgoff += start >> PAGE_SHIFT;
-	return pci_mmap_page_range(pdev, bar, vma, mmap_state, write_combine);
-}
 #endif

drivers/pci/proc.c

@@ -244,6 +244,7 @@ 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;
+	resource_size_t start, end;
 	int i, ret, write_combine = 0, res_bit = IORESOURCE_MEM;
 
 	if (!capable(CAP_SYS_RAWIO) ||
@@ -278,7 +279,11 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
 	    iomem_is_exclusive(dev->resource[i].start))
 		return -EINVAL;
 
-	ret = pci_mmap_page_range(dev, i, vma,
+	pci_resource_to_user(dev, i, &dev->resource[i], &start, &end);
+
+	/* Adjust vm_pgoff to be the offset within the resource */
+	vma->vm_pgoff -= start >> PAGE_SHIFT;
+	ret = pci_mmap_resource_range(dev, i, vma,
 				  fpriv->mmap_state, write_combine);
 	if (ret < 0)
 		return ret;

include/linux/pci.h

@@ -1909,24 +1909,14 @@ pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
 
 #include <asm/pci.h>
 
-/* These two functions provide almost identical functionality. Depending
+/*
- * on the architecture, one will be implemented as a wrapper around the
- * other (in drivers/pci/mmap.c).
- *
  * pci_mmap_resource_range() maps a specific BAR, and vm->vm_pgoff
  * is expected to be an offset within that region.
  *
- * pci_mmap_page_range() is the legacy architecture-specific interface,
- * which accepts a "user visible" resource address converted by
- * pci_resource_to_user(), as used in the legacy mmap() interface in
- * /proc/bus/pci/.
  */
 int pci_mmap_resource_range(struct pci_dev *dev, int bar,
 			    struct vm_area_struct *vma,
 			    enum pci_mmap_state mmap_state, int write_combine);
-int pci_mmap_page_range(struct pci_dev *pdev, int bar,
-			struct vm_area_struct *vma,
-			enum pci_mmap_state mmap_state, int write_combine);
 
 #ifndef arch_can_pci_mmap_wc
 #define arch_can_pci_mmap_wc()		0