drm/i915: Support for extra alignment for tiled surfaces

SKL+ needs >4K alignment for tiled surfaces, so make
intel_compute_page_offset() handle it.

The way we do it is first we compute the closest tile boundary
as before, and then figure out how many tiles we need to go
to reach the desired alignment. The difference in the offset
is then added into the x/y offsets.

v2: Be less confusing wrt. units (pixels vs. bytes) (Daniel)
v3: Use u32 for offsets
    Have intel_adjust_tile_offset() return the new offset (will be
    useful later)
    Add an offset_aligned variable (Daniel)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1455569699-27905-5-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -2463,6 +2463,35 @@ static void intel_unpin_fb_obj(struct drm_framebuffer *fb,
 	i915_gem_object_unpin_from_display_plane(obj, &view);
 }
 
+/*
+ * Adjust the tile offset by moving the difference into
+ * the x/y offsets.
+ *
+ * Input tile dimensions and pitch must already be
+ * rotated to match x and y, and in pixel units.
+ */
+static u32 intel_adjust_tile_offset(int *x, int *y,
+				    unsigned int tile_width,
+				    unsigned int tile_height,
+				    unsigned int tile_size,
+				    unsigned int pitch_tiles,
+				    u32 old_offset,
+				    u32 new_offset)
+{
+	unsigned int tiles;
+
+	WARN_ON(old_offset & (tile_size - 1));
+	WARN_ON(new_offset & (tile_size - 1));
+	WARN_ON(new_offset > old_offset);
+
+	tiles = (old_offset - new_offset) / tile_size;
+
+	*y += tiles / pitch_tiles * tile_height;
+	*x += tiles % pitch_tiles * tile_width;
+
+	return new_offset;
+}
+
 /*
  * Computes the linear offset to the base tile and adjusts
  * x, y. bytes per pixel is assumed to be a power-of-two.
@@ -2478,6 +2507,12 @@ u32 intel_compute_tile_offset(struct drm_i915_private *dev_priv,
 			      unsigned int pitch,
 			      unsigned int rotation)
 {
+	u32 offset, offset_aligned, alignment;
+
+	alignment = intel_surf_alignment(dev_priv, fb_modifier);
+	if (alignment)
+		alignment--;
+
 	if (fb_modifier != DRM_FORMAT_MOD_NONE) {
 		unsigned int tile_size, tile_width, tile_height;
 		unsigned int tile_rows, tiles, pitch_tiles;
@@ -2499,16 +2534,21 @@ u32 intel_compute_tile_offset(struct drm_i915_private *dev_priv,
 		tiles = *x / tile_width;
 		*x %= tile_width;
 
-		return (tile_rows * pitch_tiles + tiles) * tile_size;
-	} else {
-		unsigned int alignment = intel_linear_alignment(dev_priv) - 1;
-		unsigned int offset;
+		offset = (tile_rows * pitch_tiles + tiles) * tile_size;
+		offset_aligned = offset & ~alignment;
 
+		intel_adjust_tile_offset(x, y, tile_width, tile_height,
+					 tile_size, pitch_tiles,
+					 offset, offset_aligned);
+	} else {
 		offset = *y * pitch + *x * cpp;
+		offset_aligned = offset & ~alignment;
+
 		*y = (offset & alignment) / pitch;
 		*x = ((offset & alignment) - *y * pitch) / cpp;
-		return offset & ~alignment;
 	}
+
+	return offset_aligned;
 }
 
 static int i9xx_format_to_fourcc(int format)