drm/i915: Avoid allocating a vmap arena for a single page

If we want a contiguous mapping of a single page sized object, we can
forgo using vmap() and just use a regular kmap(). Note that this is only
suitable if the desired pgprot_t is compatible.

v2: Use is_vmalloc_addr()

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Dave Gordon <david.s.gordon@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460113874-17366-7-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>

1 files changed, 14 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index eaf906875cd8..f1455faecbd2 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2233,7 +2233,10 @@ i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
         list_del(&obj->global_list);
 
         if (obj->mapping) {
-                vunmap(obj->mapping);
+                if (is_vmalloc_addr(obj->mapping))
+                        vunmap(obj->mapping);
+                else
+                        kunmap(kmap_to_page(obj->mapping));
                 obj->mapping = NULL;
         }
 
@@ -2418,13 +2421,19 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj)
         i915_gem_object_pin_pages(obj);
 
         if (obj->mapping == NULL) {
-                struct sg_page_iter sg_iter;
                 struct page **pages;
-                int n;
 
-                n = obj->base.size >> PAGE_SHIFT;
-                pages = drm_malloc_gfp(n, sizeof(*pages), GFP_TEMPORARY);
+                pages = NULL;
+                if (obj->base.size == PAGE_SIZE)
+                        obj->mapping = kmap(sg_page(obj->pages->sgl));
+                else
+                        pages = drm_malloc_gfp(obj->base.size >> PAGE_SHIFT,
+                                               sizeof(*pages),
+                                               GFP_TEMPORARY);
                 if (pages != NULL) {
+                        struct sg_page_iter sg_iter;
+                        int n;
+
                         n = 0;
                         for_each_sg_page(obj->pages->sgl, &sg_iter,
                                          obj->pages->nents, 0)