drm/i915: Flush untouched framebuffers before display on !llc

On a non-llc system, the objects are created with .cache_level =
CACHE_NONE and so the transition to uncached for scanout is a no-op.
However, if the object was never written to, it will still be in the CPU
domain (having been zeroed out by shmemfs). Those cachelines need to be
flushed prior to display.

Reported-and-tested-by: Vito Caputo
Fixes: a6a7cc4b7db6 ("drm/i915: Always flush the dirty CPU cache when pinning the scanout")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: <drm-intel-fixes@lists.freedesktop.org> # v4.10-rc1+
Link: http://patchwork.freedesktop.org/patch/msgid/20170109111932.6342-1-chris@chris-wilson.co.uk
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 2522d48..f3b5cb4 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3519,7 +3519,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
        vma->display_alignment = max_t(u64, vma->display_alignment, alignment);
 
        /* Treat this as an end-of-frame, like intel_user_framebuffer_dirty() */
-       if (obj->cache_dirty) {
+       if (obj->cache_dirty || obj->base.write_domain == I915_GEM_DOMAIN_CPU) {
                i915_gem_clflush_object(obj, true);
                intel_fb_obj_flush(obj, false, ORIGIN_DIRTYFB);
        }