drm/i915: Introduce i915_gem_object_get_dma_address()

This utility function is a companion to i915_gem_object_get_page() that
uses the same cached iterator for the scatterlist to perform fast
sequential lookup of the dma address associated with any page within the
object.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 53d9e3f..0349c5f 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3118,6 +3118,23 @@ static inline int __sg_page_count(struct scatterlist *sg)
 struct page *
 i915_gem_object_get_dirty_page(struct drm_i915_gem_object *obj, int n);
 
+static inline dma_addr_t
+i915_gem_object_get_dma_address(struct drm_i915_gem_object *obj, int n)
+{
+       if (n < obj->get_page.last) {
+               obj->get_page.sg = obj->pages->sgl;
+               obj->get_page.last = 0;
+       }
+
+       while (obj->get_page.last + __sg_page_count(obj->get_page.sg) <= n) {
+               obj->get_page.last += __sg_page_count(obj->get_page.sg++);
+               if (unlikely(sg_is_chain(obj->get_page.sg)))
+                       obj->get_page.sg = sg_chain_ptr(obj->get_page.sg);
+       }
+
+       return sg_dma_address(obj->get_page.sg) + ((n - obj->get_page.last) << PAGE_SHIFT);
+}
+
 static inline struct page *
 i915_gem_object_get_page(struct drm_i915_gem_object *obj, int n)
 {