[PATCH] drm/i915: fix relaxed tiling on gen2

[Daniel Vetter <daniel.vetter@ffwll.ch>]

A tile on gen2 has a size of 2kb, stride of 128 bytes and 16 rows.

Userspace was broken and assumed 8 rows. Complain with a printk_once
and disallow such tiling requests.

Also experiments and randoms cues from i81x docs suggest that y-tiling
doesn't work with fences (it's already known to be broken on the blitter).
Original idea seems to be to use y-tiling for textures with a manually
tiling upload path. Hence also disallow y-tiling - current userspace
doesn't use it at all, anyway.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
IMO a -next patch. If people keep on complaining that .2.6.38 broke their
machines we can backport the printk_once; return -EINVAL hunk.
-Daniel

 drivers/gpu/drm/i915/i915_gem.c        |    5 +++--
 drivers/gpu/drm/i915/i915_gem_tiling.c |    9 +++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 4554b2f..bc96e70 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1452,8 +1452,9 @@ i915_gem_get_unfenced_gtt_alignment(struct drm_i915_gem_object *obj)
 	 * edge of an even tile row (where tile rows are counted as if the bo is
 	 * placed in a fenced gtt region).
 	 */
-	if (IS_GEN2(dev) ||
-	    (obj->tiling_mode == I915_TILING_Y && HAS_128_BYTE_Y_TILING(dev)))
+	if (IS_GEN2(dev))
+		tile_height = 16;
+	else if (obj->tiling_mode == I915_TILING_Y && HAS_128_BYTE_Y_TILING(dev))
 		tile_height = 32;
 	else
 		tile_height = 8;
diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
index 281ad3d..693e6e8 100644
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -190,6 +190,9 @@ i915_tiling_ok(struct drm_device *dev, int stride, int size, int tiling_mode)
 	if (tiling_mode == I915_TILING_NONE)
 		return true;
 
+	if (IS_GEN2(dev) && tiling_mode == I915_TILING_Y)
+		return false;
+
 	if (IS_GEN2(dev) ||
 	    (tiling_mode == I915_TILING_Y && HAS_128_BYTE_Y_TILING(dev)))
 		tile_width = 128;
@@ -226,6 +229,12 @@ i915_tiling_ok(struct drm_device *dev, int stride, int size, int tiling_mode)
 	if (stride < tile_width)
 		return false;
 
+	if (IS_GEN2(dev) && (size / tile_width) % 16 != 0) {
+		printk_once("broken userspace detected, "
+			    "please upgrade libdrm and xf86-video-intel\n");
+		return false;
+	}
+
 	if (stride & (stride - 1))
 		return false;
 
-- 
1.7.4.1