[Intel-gfx] [PATCH] drm/i915: Revoke partial fences when installing on the scanout

[Chris Wilson]

In commit 50349247ea80 ("drm/i915: Drop ORIGIN_GTT for untracked GTT
writes") partial mmaps were updated to indicate that writes through them
were not tracked automatically by the hardware and that the expected
subsequent manual invalidations by the application (on calling dirtyfb at
the end of the frame) take over from the hardware tracking. However, not
all applications actually call dirtyfb on the scanout after they dirty it
and so those writes through partial GTT mmaps are not being tracked and
triggering FBC updates.

Fixes: a61007a83a46 ("drm/i915: Fix partial GGTT faulting")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at intel.com>
Cc: "Zanoni, Paulo R" <paulo.r.zanoni at intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c        | 25 ++++++++++++++++++++-----
 drivers/gpu/drm/i915/i915_gem_object.h |  2 ++
 drivers/gpu/drm/i915/intel_display.c   | 10 +++++++++-
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index f379c5484a84..d51c9b209837 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1882,11 +1882,6 @@ int i915_gem_fault(struct vm_area_struct *area, struct vm_fault *vmf)
 			compute_partial_view(obj, area,
 					     page_offset, MIN_CHUNK_PAGES);
 
-		/* Userspace is now writing through an untracked VMA, abandon
-		 * all hope that the hardware is able to track future writes.
-		 */
-		obj->frontbuffer_ggtt_origin = ORIGIN_CPU;
-
 		vma = i915_gem_object_ggtt_pin(obj, &view, 0, 0, PIN_MAPPABLE);
 	}
 	if (IS_ERR(vma)) {
@@ -2015,6 +2010,26 @@ i915_gem_release_mmap(struct drm_i915_gem_object *obj)
 	intel_runtime_pm_put(i915);
 }
 
+bool i915_gem_object_has_partial_fences(struct drm_i915_gem_object *obj)
+{
+	struct i915_vma *vma;
+
+	lockdep_assert_held(&obj->base.dev->struct_mutex);
+
+	list_for_each_entry(vma, &obj->vma_list, obj_link) {
+		if (!i915_vma_is_ggtt(vma))
+			break;
+
+		if (vma->ggtt_view.type != I915_GGTT_VIEW_NORMAL)
+			continue;
+
+		if (vma->fence)
+			return true;
+	}
+
+	return false;
+}
+
 void i915_gem_runtime_suspend(struct drm_i915_private *dev_priv)
 {
 	struct drm_i915_gem_object *obj, *on;
diff --git a/drivers/gpu/drm/i915/i915_gem_object.h b/drivers/gpu/drm/i915/i915_gem_object.h
index 36e0c50e2099..03c066cbdbfd 100644
--- a/drivers/gpu/drm/i915/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/i915_gem_object.h
@@ -333,5 +333,7 @@ i915_gem_object_last_write_engine(struct drm_i915_gem_object *obj)
 	return engine;
 }
 
+bool i915_gem_object_has_partial_fences(struct drm_i915_gem_object *obj);
+
 #endif
 
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index aaec753e510e..89d8dffed546 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2236,8 +2236,16 @@ intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb, unsigned int rotation)
 		 * something and try to run the system in a "less than optimal"
 		 * mode that matches the user configuration.
 		 */
-		if (i915_vma_get_fence(vma) == 0)
+		if (i915_vma_get_fence(vma) == 0) {
 			i915_vma_pin_fence(vma);
+
+			/* Revoke any partial fences and force users of
+			 * those mmapings to transfer over to this fence
+			 * under the watchful gaze of FBC.
+			 */
+			if (i915_gem_object_has_partial_fences(obj))
+				i915_gem_release_mmap(obj);
+		}
 	}
 
 	i915_vma_get(vma);
-- 
2.11.0