drm/i915: don't force full modeset if primary plane is disabled (v2)

In a future patch, we'll allow the primary plane to be disabled by
userspace via the universal plane API.  If a modeset is requested while
the primary plane is disabled, crtc->primary->fb will be NULL which
generally triggers a full modeset (except in fastboot situations).  If
we detect that the crtc is active, but there's no primary plane fb,
we should still allow a simple plane update rather than a full modeset
if the mode isn't actually changing (after re-enabling the primary plane
of course).

v2:
 - Enable plane after set_base to avoid enabling the plane if set_base
   fails, and to make flip+enable atomic (suggested by Ville)
 - Drop BUG to WARN if we somehow enter the 'fb_changed' modeset case
   with the crtc disabled (suggested by Ville)

Reviewed-by: Chon Ming Lee <chon.ming.lee@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
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 8635bb7..d99be95 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -10562,12 +10562,17 @@ intel_set_config_compute_mode_changes(struct drm_mode_set *set,
        if (is_crtc_connector_off(set)) {
                config->mode_changed = true;
        } else if (set->crtc->primary->fb != set->fb) {
-               /* If we have no fb then treat it as a full mode set */
+               /*
+                * If we have no fb, we can only flip as long as the crtc is
+                * active, otherwise we need a full mode set.  The crtc may
+                * be active if we've only disabled the primary plane, or
+                * in fastboot situations.
+                */
                if (set->crtc->primary->fb == NULL) {
                        struct intel_crtc *intel_crtc =
                                to_intel_crtc(set->crtc);
 
-                       if (intel_crtc->active && i915.fastboot) {
+                       if (intel_crtc->active) {
                                DRM_DEBUG_KMS("crtc has no fb, will flip\n");
                                config->fb_changed = true;
                        } else {
@@ -10805,10 +10810,24 @@ static int intel_crtc_set_config(struct drm_mode_set *set)
                ret = intel_set_mode(set->crtc, set->mode,
                                     set->x, set->y, set->fb);
        } else if (config->fb_changed) {
+               struct drm_i915_private *dev_priv = dev->dev_private;
+               struct intel_crtc *intel_crtc = to_intel_crtc(set->crtc);
+
                intel_crtc_wait_for_pending_flips(set->crtc);
 
                ret = intel_pipe_set_base(set->crtc,
                                          set->x, set->y, set->fb);
+
+               /*
+                * We need to make sure the primary plane is re-enabled if it
+                * has previously been turned off.
+                */
+               if (!intel_crtc->primary_enabled && ret == 0) {
+                       WARN_ON(!intel_crtc->active);
+                       intel_enable_primary_hw_plane(dev_priv, intel_crtc->plane,
+                                                     intel_crtc->pipe);
+               }
+
                /*
                 * In the fastboot case this may be our only check of the
                 * state after boot.  It would be better to only do it on