drm/i915: flip on a no fb -> fb transition if crtc is active v3

If the crtc is active, we can simply flip a new fb onto it, provided the
other mode setting reqs are met.  Otherwise, we'll need to do a full
mode set to re-enable the crtc.

v2: check for crtc active and set mode_changed accordingly
v3: add module parameter, i915.fastboot, to control no fb -> fb flip behavior

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 6c0014d..2ab34e5 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8676,8 +8676,16 @@ intel_set_config_compute_mode_changes(struct drm_mode_set *set,
        } else if (set->crtc->fb != set->fb) {
                /* If we have no fb then treat it as a full mode set */
                if (set->crtc->fb == NULL) {
-                       DRM_DEBUG_KMS("crtc has no fb, full mode set\n");
-                       config->mode_changed = true;
+                       struct intel_crtc *intel_crtc =
+                               to_intel_crtc(set->crtc);
+
+                       if (intel_crtc->active && i915_fastboot) {
+                               DRM_DEBUG_KMS("crtc has no fb, will flip\n");
+                               config->fb_changed = true;
+                       } else {
+                               DRM_DEBUG_KMS("inactive crtc, full mode set\n");
+                               config->mode_changed = true;
+                       }
                } else if (set->fb == NULL) {
                        config->mode_changed = true;
                } else if (set->fb->pixel_format !=