drm/i915: Emit a backtrace if we attempt to rebind a pinned buffer

This debugging trace was useful for finding the fbcon regression on
i965, and it may prove useful again in future.

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

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 24ee4622484f..b0fb394b9ff4 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4198,6 +4198,10 @@ i915_gem_object_pin(struct drm_gem_object *obj, uint32_t alignment)
                 if (alignment == 0)
                         alignment = i915_gem_get_gtt_alignment(obj);
                 if (obj_priv->gtt_offset & (alignment - 1)) {
+                        WARN(obj_priv->pin_count,
+                             "bo is already pinned with incorrect alignment:"
+                             " offset=%x, req.alignment=%x\n",
+                             obj_priv->gtt_offset, alignment);
                         ret = i915_gem_object_unbind(obj);
                         if (ret)
                                 return ret;