drm/i915: Install fence register for tiled scanout on i915

With the work by Jesse Barnes to eliminate allocation of fences during
execbuffer, it becomes possible to write to the scan-out buffer with it
never acquiring a fence (simply by only ever writing to the object using
tiled GPU commands and never writing to it via the GTT). So for pre-i965
chipsets which require fenced access for tiled scan-out buffers, we need
to obtain a fence register.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 16 insertions, 4 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 028f5b66e3d8..3e1c78162119 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -828,19 +828,31 @@ intel_pipe_set_base(struct drm_crtc *crtc, int x, int y,
         }
 
         mutex_lock(&dev->struct_mutex);
-        ret = i915_gem_object_pin(intel_fb->obj, alignment);
+        ret = i915_gem_object_pin(obj, alignment);
         if (ret != 0) {
                 mutex_unlock(&dev->struct_mutex);
                 return ret;
         }
 
-        ret = i915_gem_object_set_to_gtt_domain(intel_fb->obj, 1);
+        ret = i915_gem_object_set_to_gtt_domain(obj, 1);
         if (ret != 0) {
-                i915_gem_object_unpin(intel_fb->obj);
+                i915_gem_object_unpin(obj);
                 mutex_unlock(&dev->struct_mutex);
                 return ret;
         }
 
+        /* Pre-i965 needs to install a fence for tiled scan-out */
+        if (!IS_I965G(dev) &&
+            obj_priv->fence_reg == I915_FENCE_REG_NONE &&
+            obj_priv->tiling_mode != I915_TILING_NONE) {
+                ret = i915_gem_object_get_fence_reg(obj);
+                if (ret != 0) {
+                        i915_gem_object_unpin(obj);
+                        mutex_unlock(&dev->struct_mutex);
+                        return ret;
+                }
+        }
+
         dspcntr = I915_READ(dspcntr_reg);
         /* Mask out pixel format bits in case we change it */
         dspcntr &= ~DISPPLANE_PIXFORMAT_MASK;
@@ -860,7 +872,7 @@ intel_pipe_set_base(struct drm_crtc *crtc, int x, int y,
                 break;
         default:
                 DRM_ERROR("Unknown color depth\n");
-                i915_gem_object_unpin(intel_fb->obj);
+                i915_gem_object_unpin(obj);
                 mutex_unlock(&dev->struct_mutex);
                 return -EINVAL;
         }