12 files changed, 390 insertions, 105 deletions

diff --git a/Documentation/io-mapping.txt b/Documentation/io-mapping.txt
new file mode 100644
index 000000000000..473e43b2d588
--- /dev/null
+++ b/Documentation/io-mapping.txt
@@ -0,0 +1,82 @@
+The io_mapping functions in linux/io-mapping.h provide an abstraction for
+efficiently mapping small regions of an I/O device to the CPU. The initial
+usage is to support the large graphics aperture on 32-bit processors where
+ioremap_wc cannot be used to statically map the entire aperture to the CPU
+as it would consume too much of the kernel address space.
+
+A mapping object is created during driver initialization using
+
+        struct io_mapping *io_mapping_create_wc(unsigned long base,
+                                                unsigned long size)
+
+                'base' is the bus address of the region to be made
+                mappable, while 'size' indicates how large a mapping region to
+                enable. Both are in bytes.
+
+                This _wc variant provides a mapping which may only be used
+                with the io_mapping_map_atomic_wc or io_mapping_map_wc.
+
+With this mapping object, individual pages can be mapped either atomically
+or not, depending on the necessary scheduling environment. Of course, atomic
+maps are more efficient:
+
+        void *io_mapping_map_atomic_wc(struct io_mapping *mapping,
+                                       unsigned long offset)
+
+                'offset' is the offset within the defined mapping region.
+                Accessing addresses beyond the region specified in the
+                creation function yields undefined results. Using an offset
+                which is not page aligned yields an undefined result. The
+                return value points to a single page in CPU address space.
+
+                This _wc variant returns a write-combining map to the
+                page and may only be used with mappings created by
+                io_mapping_create_wc
+
+                Note that the task may not sleep while holding this page
+                mapped.
+
+        void io_mapping_unmap_atomic(void *vaddr)
+
+                'vaddr' must be the the value returned by the last
+                io_mapping_map_atomic_wc call. This unmaps the specified
+                page and allows the task to sleep once again.
+
+If you need to sleep while holding the lock, you can use the non-atomic
+variant, although they may be significantly slower.
+
+        void *io_mapping_map_wc(struct io_mapping *mapping,
+                                unsigned long offset)
+
+                This works like io_mapping_map_atomic_wc except it allows
+                the task to sleep while holding the page mapped.
+
+        void io_mapping_unmap(void *vaddr)
+
+                This works like io_mapping_unmap_atomic, except it is used
+                for pages mapped with io_mapping_map_wc.
+
+At driver close time, the io_mapping object must be freed:
+
+        void io_mapping_free(struct io_mapping *mapping)
+
+Current Implementation:
+
+The initial implementation of these functions uses existing mapping
+mechanisms and so provides only an abstraction layer and no new
+functionality.
+
+On 64-bit processors, io_mapping_create_wc calls ioremap_wc for the whole
+range, creating a permanent kernel-visible mapping to the resource. The
+map_atomic and map functions add the requested offset to the base of the
+virtual address returned by ioremap_wc.
+
+On 32-bit processors with HIGHMEM defined, io_mapping_map_atomic_wc uses
+kmap_atomic_pfn to map the specified page in an atomic fashion;
+kmap_atomic_pfn isn't really supposed to be used with device pages, but it
+provides an efficient mapping for this usage.
+
+On 32-bit processors without HIGHMEM defined, io_mapping_map_atomic_wc and
+io_mapping_map_wc both use ioremap_wc, a terribly inefficient function which
+performs an IPI to inform all processors about the new mapping. This results
+in a significant performance penalty.
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6f20718d3156..e60c59b81bdd 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1894,6 +1894,10 @@ config SYSVIPC_COMPAT
 endmenu
 
 
+config HAVE_ATOMIC_IOMAP
+        def_bool y
+        depends on X86_32
+
 source "net/Kconfig"
 
 source "drivers/Kconfig"
diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
index 8668a94f850e..23696d44a0af 100644
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -9,6 +9,10 @@
 
 extern int fixmaps_set;
 
+extern pte_t *kmap_pte;
+extern pgprot_t kmap_prot;
+extern pte_t *pkmap_page_table;
+
 void __native_set_fixmap(enum fixed_addresses idx, pte_t pte);
 void native_set_fixmap(enum fixed_addresses idx,
                        unsigned long phys, pgprot_t flags);
diff --git a/arch/x86/include/asm/fixmap_32.h b/arch/x86/include/asm/fixmap_32.h
index 09f29ab5c139..c7115c1d7217 100644
--- a/arch/x86/include/asm/fixmap_32.h
+++ b/arch/x86/include/asm/fixmap_32.h
@@ -28,10 +28,8 @@ extern unsigned long __FIXADDR_TOP;
 #include <asm/acpi.h>
 #include <asm/apicdef.h>
 #include <asm/page.h>
-#ifdef CONFIG_HIGHMEM
 #include <linux/threads.h>
 #include <asm/kmap_types.h>
-#endif
 
 /*
  * Here we define all the compile-time 'special' virtual
@@ -75,10 +73,8 @@ enum fixed_addresses {
 #ifdef CONFIG_X86_CYCLONE_TIMER
         FIX_CYCLONE_TIMER, /*cyclone timer register*/
 #endif
-#ifdef CONFIG_HIGHMEM
         FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
         FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
-#endif
 #ifdef CONFIG_PCI_MMCONFIG
         FIX_PCIE_MCFG,
 #endif
diff --git a/arch/x86/include/asm/highmem.h b/arch/x86/include/asm/highmem.h
index a3b3b7c3027b..bf9276bea660 100644
--- a/arch/x86/include/asm/highmem.h
+++ b/arch/x86/include/asm/highmem.h
@@ -25,14 +25,11 @@
 #include <asm/kmap_types.h>
 #include <asm/tlbflush.h>
 #include <asm/paravirt.h>
+#include <asm/fixmap.h>
 
 /* declarations for highmem.c */
 extern unsigned long highstart_pfn, highend_pfn;
 
-extern pte_t *kmap_pte;
-extern pgprot_t kmap_prot;
-extern pte_t *pkmap_page_table;
-
 /*
  * Right now we initialize only a single pte table. It can be extended
  * easily, subsequent pte tables have to be allocated in one physical
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 59f89b434b45..fea4565ff576 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -1,7 +1,7 @@
 obj-y   :=  init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o \
             pat.o pgtable.o gup.o
 
-obj-$(CONFIG_X86_32)            += pgtable_32.o
+obj-$(CONFIG_X86_32)            += pgtable_32.o iomap_32.o
 
 obj-$(CONFIG_HUGETLB_PAGE)      += hugetlbpage.o
 obj-$(CONFIG_X86_PTDUMP)        += dump_pagetables.o
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 8396868e82c5..c483f4242079 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -334,7 +334,6 @@ int devmem_is_allowed(unsigned long pagenr)
         return 0;
 }
 
-#ifdef CONFIG_HIGHMEM
 pte_t *kmap_pte;
 pgprot_t kmap_prot;
 
@@ -357,6 +356,7 @@ static void __init kmap_init(void)
         kmap_prot = PAGE_KERNEL;
 }
 
+#ifdef CONFIG_HIGHMEM
 static void __init permanent_kmaps_init(pgd_t *pgd_base)
 {
         unsigned long vaddr;
@@ -436,7 +436,6 @@ static void __init set_highmem_pages_init(void)
 #endif /* !CONFIG_NUMA */
 
 #else
-# define kmap_init()                            do { } while (0)
 # define permanent_kmaps_init(pgd_base)         do { } while (0)
 # define set_highmem_pages_init()       do { } while (0)
 #endif /* CONFIG_HIGHMEM */
diff --git a/arch/x86/mm/iomap_32.c b/arch/x86/mm/iomap_32.c
new file mode 100644
index 000000000000..d0151d8ce452
--- /dev/null
+++ b/arch/x86/mm/iomap_32.c
@@ -0,0 +1,59 @@
+/*
+ * Copyright © 2008 Ingo Molnar
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include <asm/iomap.h>
+#include <linux/module.h>
+
+/* Map 'pfn' using fixed map 'type' and protections 'prot'
+ */
+void *
+iomap_atomic_prot_pfn(unsigned long pfn, enum km_type type, pgprot_t prot)
+{
+        enum fixed_addresses idx;
+        unsigned long vaddr;
+
+        pagefault_disable();
+
+        idx = type + KM_TYPE_NR*smp_processor_id();
+        vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+        set_pte(kmap_pte-idx, pfn_pte(pfn, prot));
+        arch_flush_lazy_mmu_mode();
+
+        return (void*) vaddr;
+}
+EXPORT_SYMBOL_GPL(iomap_atomic_prot_pfn);
+
+void
+iounmap_atomic(void *kvaddr, enum km_type type)
+{
+        unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
+        enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
+
+        /*
+         * Force other mappings to Oops if they'll try to access this pte
+         * without first remap it.  Keeping stale mappings around is a bad idea
+         * also, in case the page changes cacheability attributes or becomes
+         * a protected page in a hypervisor.
+         */
+        if (vaddr == __fix_to_virt(FIX_KMAP_BEGIN+idx))
+                kpte_clear_flush(kmap_pte-idx, vaddr);
+
+        arch_flush_lazy_mmu_mode();
+        pagefault_enable();
+}
+EXPORT_SYMBOL_GPL(iounmap_atomic);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index cc8a9f3f7a60..572dcd0e3e0d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -31,6 +31,7 @@
 #define _I915_DRV_H_
 
 #include "i915_reg.h"
+#include <linux/io-mapping.h>
 
 /* General customization:
  */
@@ -246,6 +247,8 @@ typedef struct drm_i915_private {
         struct {
                 struct drm_mm gtt_space;
 
+                struct io_mapping *gtt_mapping;
+
                 /**
                  * List of objects currently involved in rendering from the
                  * ringbuffer.
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index c1733ac4a7f5..b0ec73fa6a93 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -193,35 +193,50 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
         return 0;
 }
 
-/*
- * Try to write quickly with an atomic kmap. Return true on success.
- *
- * If this fails (which includes a partial write), we'll redo the whole
- * thing with the slow version.
- *
- * This is a workaround for the low performance of iounmap (approximate
- * 10% cpu cost on normal 3D workloads).  kmap_atomic on HIGHMEM kernels
- * happens to let us map card memory without taking IPIs.  When the vmap
- * rework lands we should be able to dump this hack.
+/* This is the fast write path which cannot handle
+ * page faults in the source data
  */
-static inline int fast_user_write(unsigned long pfn, char __user *user_data,
-                                  int l, int o)
+
+static inline int
+fast_user_write(struct io_mapping *mapping,
+                loff_t page_base, int page_offset,
+                char __user *user_data,
+                int length)
 {
-#ifdef CONFIG_HIGHMEM
-        unsigned long unwritten;
         char *vaddr_atomic;
+        unsigned long unwritten;
 
-        vaddr_atomic = kmap_atomic_pfn(pfn, KM_USER0);
-#if WATCH_PWRITE
-        DRM_INFO("pwrite i %d o %d l %d pfn %ld vaddr %p\n",
-                 i, o, l, pfn, vaddr_atomic);
-#endif
-        unwritten = __copy_from_user_inatomic_nocache(vaddr_atomic + o, user_data, l);
-        kunmap_atomic(vaddr_atomic, KM_USER0);
-        return !unwritten;
-#else
+        vaddr_atomic = io_mapping_map_atomic_wc(mapping, page_base);
+        unwritten = __copy_from_user_inatomic_nocache(vaddr_atomic + page_offset,
+                                                      user_data, length);
+        io_mapping_unmap_atomic(vaddr_atomic);
+        if (unwritten)
+                return -EFAULT;
+        return 0;
+}
+
+/* Here's the write path which can sleep for
+ * page faults
+ */
+
+static inline int
+slow_user_write(struct io_mapping *mapping,
+                loff_t page_base, int page_offset,
+                char __user *user_data,
+                int length)
+{
+        char __iomem *vaddr;
+        unsigned long unwritten;
+
+        vaddr = io_mapping_map_wc(mapping, page_base);
+        if (vaddr == NULL)
+                return -EFAULT;
+        unwritten = __copy_from_user(vaddr + page_offset,
+                                     user_data, length);
+        io_mapping_unmap(vaddr);
+        if (unwritten)
+                return -EFAULT;
         return 0;
-#endif
 }
 
 static int
@@ -230,10 +245,12 @@ i915_gem_gtt_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
                     struct drm_file *file_priv)
 {
         struct drm_i915_gem_object *obj_priv = obj->driver_private;
+        drm_i915_private_t *dev_priv = dev->dev_private;
         ssize_t remain;
-        loff_t offset;
+        loff_t offset, page_base;
         char __user *user_data;
-        int ret = 0;
+        int page_offset, page_length;
+        int ret;
 
         user_data = (char __user *) (uintptr_t) args->data_ptr;
         remain = args->size;
@@ -257,57 +274,37 @@ i915_gem_gtt_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
         obj_priv->dirty = 1;
 
         while (remain > 0) {
-                unsigned long pfn;
-                int i, o, l;
-
                 /* Operation in this page
                  *
-                 * i = page number
-                 * o = offset within page
-                 * l = bytes to copy
+                 * page_base = page offset within aperture
+                 * page_offset = offset within page
+                 * page_length = bytes to copy for this page
                  */
-                i = offset >> PAGE_SHIFT;
-                o = offset & (PAGE_SIZE-1);
-                l = remain;
-                if ((o + l) > PAGE_SIZE)
-                        l = PAGE_SIZE - o;
-
-                pfn = (dev->agp->base >> PAGE_SHIFT) + i;
-
-                if (!fast_user_write(pfn, user_data, l, o)) {
-                        unsigned long unwritten;
-                        char __iomem *vaddr;
-
-                        vaddr = ioremap_wc(pfn << PAGE_SHIFT, PAGE_SIZE);
-#if WATCH_PWRITE
-                        DRM_INFO("pwrite slow i %d o %d l %d "
-                                 "pfn %ld vaddr %p\n",
-                                 i, o, l, pfn, vaddr);
-#endif
-                        if (vaddr == NULL) {
-                                ret = -EFAULT;
-                                goto fail;
-                        }
-                        unwritten = __copy_from_user(vaddr + o, user_data, l);
-#if WATCH_PWRITE
-                        DRM_INFO("unwritten %ld\n", unwritten);
-#endif
-                        iounmap(vaddr);
-                        if (unwritten) {
-                                ret = -EFAULT;
+                page_base = (offset & ~(PAGE_SIZE-1));
+                page_offset = offset & (PAGE_SIZE-1);
+                page_length = remain;
+                if ((page_offset + remain) > PAGE_SIZE)
+                        page_length = PAGE_SIZE - page_offset;
+
+                ret = fast_user_write (dev_priv->mm.gtt_mapping, page_base,
+                                       page_offset, user_data, page_length);
+
+                /* If we get a fault while copying data, then (presumably) our
+                 * source page isn't available. In this case, use the
+                 * non-atomic function
+                 */
+                if (ret) {
+                        ret = slow_user_write (dev_priv->mm.gtt_mapping,
+                                               page_base, page_offset,
+                                               user_data, page_length);
+                        if (ret)
                                 goto fail;
-                        }
                 }
 
-                remain -= l;
-                user_data += l;
-                offset += l;
+                remain -= page_length;
+                user_data += page_length;
+                offset += page_length;
         }
-#if WATCH_PWRITE && 1
-        i915_gem_clflush_object(obj);
-        i915_gem_dump_object(obj, args->offset + args->size, __func__, ~0);
-        i915_gem_clflush_object(obj);
-#endif
 
 fail:
         i915_gem_object_unpin(obj);
@@ -1525,12 +1522,12 @@ i915_gem_object_pin_and_relocate(struct drm_gem_object *obj,
                                  struct drm_i915_gem_exec_object *entry)
 {
         struct drm_device *dev = obj->dev;
+        drm_i915_private_t *dev_priv = dev->dev_private;
         struct drm_i915_gem_relocation_entry reloc;
         struct drm_i915_gem_relocation_entry __user *relocs;
         struct drm_i915_gem_object *obj_priv = obj->driver_private;
         int i, ret;
-        uint32_t last_reloc_offset = -1;
-        void __iomem *reloc_page = NULL;
+        void __iomem *reloc_page;
 
         /* Choose the GTT offset for our buffer and put it there. */
         ret = i915_gem_object_pin(obj, (uint32_t) entry->alignment);
@@ -1653,26 +1650,11 @@ i915_gem_object_pin_and_relocate(struct drm_gem_object *obj,
                  * perform.
                  */
                 reloc_offset = obj_priv->gtt_offset + reloc.offset;
-                if (reloc_page == NULL ||
-                    (last_reloc_offset & ~(PAGE_SIZE - 1)) !=
-                    (reloc_offset & ~(PAGE_SIZE - 1))) {
-                        if (reloc_page != NULL)
-                                iounmap(reloc_page);
-
-                        reloc_page = ioremap_wc(dev->agp->base +
-                                                (reloc_offset &
-                                                 ~(PAGE_SIZE - 1)),
-                                                PAGE_SIZE);
-                        last_reloc_offset = reloc_offset;
-                        if (reloc_page == NULL) {
-                                drm_gem_object_unreference(target_obj);
-                                i915_gem_object_unpin(obj);
-                                return -ENOMEM;
-                        }
-                }
-
+                reloc_page = io_mapping_map_atomic_wc(dev_priv->mm.gtt_mapping,
+                                                      (reloc_offset &
+                                                       ~(PAGE_SIZE - 1)));
                 reloc_entry = (uint32_t __iomem *)(reloc_page +
-                                           (reloc_offset & (PAGE_SIZE - 1)));
+                                                   (reloc_offset & (PAGE_SIZE - 1)));
                 reloc_val = target_obj_priv->gtt_offset + reloc.delta;
 
 #if WATCH_BUF
@@ -1681,6 +1663,7 @@ i915_gem_object_pin_and_relocate(struct drm_gem_object *obj,
                           readl(reloc_entry), reloc_val);
 #endif
                 writel(reloc_val, reloc_entry);
+                io_mapping_unmap_atomic(reloc_page);
 
                 /* Write the updated presumed offset for this entry back out
                  * to the user.
@@ -1696,9 +1679,6 @@ i915_gem_object_pin_and_relocate(struct drm_gem_object *obj,
                 drm_gem_object_unreference(target_obj);
         }
 
-        if (reloc_page != NULL)
-                iounmap(reloc_page);
-
 #if WATCH_BUF
         if (0)
                 i915_gem_dump_object(obj, 128, __func__, ~0);
@@ -2540,6 +2520,10 @@ i915_gem_entervt_ioctl(struct drm_device *dev, void *data,
         if (ret != 0)
                 return ret;
 
+        dev_priv->mm.gtt_mapping = io_mapping_create_wc(dev->agp->base,
+                                                        dev->agp->agp_info.aper_size
+                                                        * 1024 * 1024);
+
         mutex_lock(&dev->struct_mutex);
         BUG_ON(!list_empty(&dev_priv->mm.active_list));
         BUG_ON(!list_empty(&dev_priv->mm.flushing_list));
@@ -2557,11 +2541,13 @@ int
 i915_gem_leavevt_ioctl(struct drm_device *dev, void *data,
                        struct drm_file *file_priv)
 {
+        drm_i915_private_t *dev_priv = dev->dev_private;
         int ret;
 
         ret = i915_gem_idle(dev);
         drm_irq_uninstall(dev);
 
+        io_mapping_free(dev_priv->mm.gtt_mapping);
         return ret;
 }
 
diff --git a/include/asm-x86/iomap.h b/include/asm-x86/iomap.h
new file mode 100644
index 000000000000..c1f06289b14b
--- /dev/null
+++ b/include/asm-x86/iomap.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright © 2008 Ingo Molnar
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/uaccess.h>
+#include <asm/cacheflush.h>
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+
+void *
+iomap_atomic_prot_pfn(unsigned long pfn, enum km_type type, pgprot_t prot);
+
+void
+iounmap_atomic(void *kvaddr, enum km_type type);
diff --git a/include/linux/io-mapping.h b/include/linux/io-mapping.h
new file mode 100644
index 000000000000..82df31726a54
--- /dev/null
+++ b/include/linux/io-mapping.h
@@ -0,0 +1,125 @@
+/*
+ * Copyright © 2008 Keith Packard <keithp@keithp.com>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#ifndef _LINUX_IO_MAPPING_H
+#define _LINUX_IO_MAPPING_H
+
+#include <linux/types.h>
+#include <asm/io.h>
+#include <asm/page.h>
+#include <asm/iomap.h>
+
+/*
+ * The io_mapping mechanism provides an abstraction for mapping
+ * individual pages from an io device to the CPU in an efficient fashion.
+ *
+ * See Documentation/io_mapping.txt
+ */
+
+/* this struct isn't actually defined anywhere */
+struct io_mapping;
+
+#ifdef CONFIG_HAVE_ATOMIC_IOMAP
+
+/*
+ * For small address space machines, mapping large objects
+ * into the kernel virtual space isn't practical. Where
+ * available, use fixmap support to dynamically map pages
+ * of the object at run time.
+ */
+
+static inline struct io_mapping *
+io_mapping_create_wc(unsigned long base, unsigned long size)
+{
+        return (struct io_mapping *) base;
+}
+
+static inline void
+io_mapping_free(struct io_mapping *mapping)
+{
+}
+
+/* Atomic map/unmap */
+static inline void *
+io_mapping_map_atomic_wc(struct io_mapping *mapping, unsigned long offset)
+{
+        offset += (unsigned long) mapping;
+        return iomap_atomic_prot_pfn(offset >> PAGE_SHIFT, KM_USER0,
+                                     __pgprot(__PAGE_KERNEL_WC));
+}
+
+static inline void
+io_mapping_unmap_atomic(void *vaddr)
+{
+        iounmap_atomic(vaddr, KM_USER0);
+}
+
+static inline void *
+io_mapping_map_wc(struct io_mapping *mapping, unsigned long offset)
+{
+        offset += (unsigned long) mapping;
+        return ioremap_wc(offset, PAGE_SIZE);
+}
+
+static inline void
+io_mapping_unmap(void *vaddr)
+{
+        iounmap(vaddr);
+}
+
+#else
+
+/* Create the io_mapping object*/
+static inline struct io_mapping *
+io_mapping_create_wc(unsigned long base, unsigned long size)
+{
+        return (struct io_mapping *) ioremap_wc(base, size);
+}
+
+static inline void
+io_mapping_free(struct io_mapping *mapping)
+{
+        iounmap(mapping);
+}
+
+/* Atomic map/unmap */
+static inline void *
+io_mapping_map_atomic_wc(struct io_mapping *mapping, unsigned long offset)
+{
+        return ((char *) mapping) + offset;
+}
+
+static inline void
+io_mapping_unmap_atomic(void *vaddr)
+{
+}
+
+/* Non-atomic map/unmap */
+static inline void *
+io_mapping_map_wc(struct io_mapping *mapping, unsigned long offset)
+{
+        return ((char *) mapping) + offset;
+}
+
+static inline void
+io_mapping_unmap(void *vaddr)
+{
+}
+
+#endif /* HAVE_ATOMIC_IOMAP */
+
+#endif /* _LINUX_IO_MAPPING_H */