[PATCH 034/131] drm/i915: Choose partial chunksize based on tile row size

[Chris Wilson]

In order to support setting up fences for partial mappings of an object,
we have to align those mappings with the fence. The minimum chunksize we
choose is at least the size of a single tile row.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index ec1a200fe0d8..1dd18608adac 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1650,6 +1650,16 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
 	return 0;
 }
 
+static unsigned int tile_row_pages(struct drm_i915_gem_object *obj)
+{
+	u64 size;
+
+	size = i915_gem_object_get_stride(obj);
+	size *= i915_gem_object_get_tiling(obj) == I915_TILING_Y ? 32 : 8;
+
+	return size >> PAGE_SHIFT;
+}
+
 /**
  * i915_gem_fault - fault a page into the GTT
  * @vma: VMA in question
@@ -1708,7 +1718,11 @@ int i915_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	/* Use a partial view if the object is bigger than the aperture. */
 	if (obj->base.size >= dev_priv->ggtt.mappable_end &&
 	    !i915_gem_object_is_tiled(obj)) {
-		static const unsigned int chunk_size = 256; // 1 MiB
+		unsigned int chunk_size;
+
+		chunk_size = 256; /* 1 MiB */
+		if (i915_gem_object_is_tiled(obj))
+			chunk_size = max(chunk_size, tile_row_pages(obj));
 
 		memset(&view, 0, sizeof(view));
 		view.type = I915_GGTT_VIEW_PARTIAL;
-- 
2.8.1