hw_entry->start, hw_entry->end);
        }
 
-       /* cursor */
-       hw_entry = &hw_ddb.plane[pipe][PLANE_CURSOR];
-       sw_entry = &sw_ddb->plane[pipe][PLANE_CURSOR];
-
-       if (!skl_ddb_entry_equal(hw_entry, sw_entry)) {
-               DRM_ERROR("mismatch in DDB state pipe %c cursor "
-                         "(expected (%u,%u), found (%u,%u))\n",
-                         pipe_name(pipe),
-                         sw_entry->start, sw_entry->end,
-                         hw_entry->start, hw_entry->end);
+       /*
+        * cursor
+        * If the cursor plane isn't active, we may not have updated it's ddb
+        * allocation. In that case since the ddb allocation will be updated
+        * once the plane becomes visible, we can skip this check
+        */
+       if (intel_crtc->cursor_addr) {
+               hw_entry = &hw_ddb.plane[pipe][PLANE_CURSOR];
+               sw_entry = &sw_ddb->plane[pipe][PLANE_CURSOR];
+
+               if (!skl_ddb_entry_equal(hw_entry, sw_entry)) {
+                       DRM_ERROR("mismatch in DDB state pipe %c cursor "
+                                 "(expected (%u,%u), found (%u,%u))\n",
+                                 pipe_name(pipe),
+                                 sw_entry->start, sw_entry->end,
+                                 hw_entry->start, hw_entry->end);
+               }
        }
 }
 
        }
 }
 
+static void skl_update_crtcs(struct drm_atomic_state *state,
+                            unsigned int *crtc_vblank_mask)
+{
+       struct drm_device *dev = state->dev;
+       struct drm_i915_private *dev_priv = to_i915(dev);
+       struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
+       struct drm_crtc *crtc;
+       struct drm_crtc_state *old_crtc_state;
+       struct skl_ddb_allocation *new_ddb = &intel_state->wm_results.ddb;
+       struct skl_ddb_allocation *cur_ddb = &dev_priv->wm.skl_hw.ddb;
+       unsigned int updated = 0;
+       bool progress;
+       enum pipe pipe;
+
+       /*
+        * Whenever the number of active pipes changes, we need to make sure we
+        * update the pipes in the right order so that their ddb allocations
+        * never overlap with eachother inbetween CRTC updates. Otherwise we'll
+        * cause pipe underruns and other bad stuff.
+        */
+       do {
+               int i;
+               progress = false;
+
+               for_each_crtc_in_state(state, crtc, old_crtc_state, i) {
+                       bool vbl_wait = false;
+                       unsigned int cmask = drm_crtc_mask(crtc);
+                       pipe = to_intel_crtc(crtc)->pipe;
+
+                       if (updated & cmask || !crtc->state->active)
+                               continue;
+                       if (skl_ddb_allocation_overlaps(state, cur_ddb, new_ddb,
+                                                       pipe))
+                               continue;
+
+                       updated |= cmask;
+
+                       /*
+                        * If this is an already active pipe, it's DDB changed,
+                        * and this isn't the last pipe that needs updating
+                        * then we need to wait for a vblank to pass for the
+                        * new ddb allocation to take effect.
+                        */
+                       if (!skl_ddb_allocation_equals(cur_ddb, new_ddb, pipe) &&
+                           !crtc->state->active_changed &&
+                           intel_state->wm_results.dirty_pipes != updated)
+                               vbl_wait = true;
+
+                       intel_update_crtc(crtc, state, old_crtc_state,
+                                         crtc_vblank_mask);
+
+                       if (vbl_wait)
+                               intel_wait_for_vblank(dev, pipe);
+
+                       progress = true;
+               }
+       } while (progress);
+}
+
 static void intel_atomic_commit_tail(struct drm_atomic_state *state)
 {
        struct drm_device *dev = state->dev;
                dev_priv->display.crtc_disable = i9xx_crtc_disable;
        }
 
-       dev_priv->display.update_crtcs = intel_update_crtcs;
-
        /* Returns the core display clock speed */
        if (IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv))
                dev_priv->display.get_display_clock_speed =
                        skl_modeset_calc_cdclk;
        }
 
+       if (dev_priv->info.gen >= 9)
+               dev_priv->display.update_crtcs = skl_update_crtcs;
+       else
+               dev_priv->display.update_crtcs = intel_update_crtcs;
+
        switch (INTEL_INFO(dev_priv)->gen) {
        case 2:
                dev_priv->display.queue_flip = intel_gen2_queue_flip;
 
                           wm->plane[pipe][plane][level]);
        }
        I915_WRITE(PLANE_WM_TRANS(pipe, plane), wm->plane_trans[pipe][plane]);
+
+       skl_ddb_entry_write(dev_priv, PLANE_BUF_CFG(pipe, plane),
+                           &wm->ddb.plane[pipe][plane]);
+       skl_ddb_entry_write(dev_priv, PLANE_NV12_BUF_CFG(pipe, plane),
+                           &wm->ddb.y_plane[pipe][plane]);
 }
 
 void skl_write_cursor_wm(struct intel_crtc *intel_crtc,
                           wm->plane[pipe][PLANE_CURSOR][level]);
        }
        I915_WRITE(CUR_WM_TRANS(pipe), wm->plane_trans[pipe][PLANE_CURSOR]);
-}
-
-static void skl_write_wm_values(struct drm_i915_private *dev_priv,
-                               const struct skl_wm_values *new)
-{
-       struct drm_device *dev = &dev_priv->drm;
-       struct intel_crtc *crtc;
-
-       for_each_intel_crtc(dev, crtc) {
-               int i;
-               enum pipe pipe = crtc->pipe;
-
-               if ((new->dirty_pipes & drm_crtc_mask(&crtc->base)) == 0)
-                       continue;
-               if (!crtc->active)
-                       continue;
-
-               for (i = 0; i < intel_num_planes(crtc); i++) {
-                       skl_ddb_entry_write(dev_priv,
-                                           PLANE_BUF_CFG(pipe, i),
-                                           &new->ddb.plane[pipe][i]);
-                       skl_ddb_entry_write(dev_priv,
-                                           PLANE_NV12_BUF_CFG(pipe, i),
-                                           &new->ddb.y_plane[pipe][i]);
-               }
 
-               skl_ddb_entry_write(dev_priv, CUR_BUF_CFG(pipe),
-                                   &new->ddb.plane[pipe][PLANE_CURSOR]);
-       }
+       skl_ddb_entry_write(dev_priv, CUR_BUF_CFG(pipe),
+                           &wm->ddb.plane[pipe][PLANE_CURSOR]);
 }
 
-/*
- * When setting up a new DDB allocation arrangement, we need to correctly
- * sequence the times at which the new allocations for the pipes are taken into
- * account or we'll have pipes fetching from space previously allocated to
- * another pipe.
- *
- * Roughly the sequence looks like:
- *  1. re-allocate the pipe(s) with the allocation being reduced and not
- *     overlapping with a previous light-up pipe (another way to put it is:
- *     pipes with their new allocation strickly included into their old ones).
- *  2. re-allocate the other pipes that get their allocation reduced
- *  3. allocate the pipes having their allocation increased
- *
- * Steps 1. and 2. are here to take care of the following case:
- * - Initially DDB looks like this:
- *     |   B    |   C    |
- * - enable pipe A.
- * - pipe B has a reduced DDB allocation that overlaps with the old pipe C
- *   allocation
- *     |  A  |  B  |  C  |
- *
- * We need to sequence the re-allocation: C, B, A (and not B, C, A).
- */
-
-static void
-skl_wm_flush_pipe(struct drm_i915_private *dev_priv, enum pipe pipe, int pass)
+bool skl_ddb_allocation_equals(const struct skl_ddb_allocation *old,
+                              const struct skl_ddb_allocation *new,
+                              enum pipe pipe)
 {
-       int plane;
-
-       DRM_DEBUG_KMS("flush pipe %c (pass %d)\n", pipe_name(pipe), pass);
-
-       for_each_plane(dev_priv, pipe, plane) {
-               I915_WRITE(PLANE_SURF(pipe, plane),
-                          I915_READ(PLANE_SURF(pipe, plane)));
-       }
-       I915_WRITE(CURBASE(pipe), I915_READ(CURBASE(pipe)));
+       return new->pipe[pipe].start == old->pipe[pipe].start &&
+              new->pipe[pipe].end == old->pipe[pipe].end;
 }
 
-static bool
-skl_ddb_allocation_included(const struct skl_ddb_allocation *old,
-                           const struct skl_ddb_allocation *new,
-                           enum pipe pipe)
+static inline bool skl_ddb_entries_overlap(const struct skl_ddb_entry *a,
+                                          const struct skl_ddb_entry *b)
 {
-       uint16_t old_size, new_size;
-
-       old_size = skl_ddb_entry_size(&old->pipe[pipe]);
-       new_size = skl_ddb_entry_size(&new->pipe[pipe]);
-
-       return old_size != new_size &&
-              new->pipe[pipe].start >= old->pipe[pipe].start &&
-              new->pipe[pipe].end <= old->pipe[pipe].end;
+       return a->start < b->end && b->start < a->end;
 }
 
-static void skl_flush_wm_values(struct drm_i915_private *dev_priv,
-                               struct skl_wm_values *new_values)
+bool skl_ddb_allocation_overlaps(struct drm_atomic_state *state,
+                                const struct skl_ddb_allocation *old,
+                                const struct skl_ddb_allocation *new,
+                                enum pipe pipe)
 {
-       struct drm_device *dev = &dev_priv->drm;
-       struct skl_ddb_allocation *cur_ddb, *new_ddb;
-       bool reallocated[I915_MAX_PIPES] = {};
-       struct intel_crtc *crtc;
-       enum pipe pipe;
-
-       new_ddb = &new_values->ddb;
-       cur_ddb = &dev_priv->wm.skl_hw.ddb;
-
-       /*
-        * First pass: flush the pipes with the new allocation contained into
-        * the old space.
-        *
-        * We'll wait for the vblank on those pipes to ensure we can safely
-        * re-allocate the freed space without this pipe fetching from it.
-        */
-       for_each_intel_crtc(dev, crtc) {
-               if (!crtc->active)
-                       continue;
-
-               pipe = crtc->pipe;
-
-               if (!skl_ddb_allocation_included(cur_ddb, new_ddb, pipe))
-                       continue;
-
-               skl_wm_flush_pipe(dev_priv, pipe, 1);
-               intel_wait_for_vblank(dev, pipe);
-
-               reallocated[pipe] = true;
-       }
-
-
-       /*
-        * Second pass: flush the pipes that are having their allocation
-        * reduced, but overlapping with a previous allocation.
-        *
-        * Here as well we need to wait for the vblank to make sure the freed
-        * space is not used anymore.
-        */
-       for_each_intel_crtc(dev, crtc) {
-               if (!crtc->active)
-                       continue;
+       struct drm_device *dev = state->dev;
+       struct intel_crtc *intel_crtc;
+       enum pipe otherp;
 
-               pipe = crtc->pipe;
+       for_each_intel_crtc(dev, intel_crtc) {
+               otherp = intel_crtc->pipe;
 
-               if (reallocated[pipe])
+               if (otherp == pipe)
                        continue;
 
-               if (skl_ddb_entry_size(&new_ddb->pipe[pipe]) <
-                   skl_ddb_entry_size(&cur_ddb->pipe[pipe])) {
-                       skl_wm_flush_pipe(dev_priv, pipe, 2);
-                       intel_wait_for_vblank(dev, pipe);
-                       reallocated[pipe] = true;
-               }
+               if (skl_ddb_entries_overlap(&new->pipe[pipe],
+                                           &old->pipe[otherp]))
+                       return true;
        }
 
-       /*
-        * Third pass: flush the pipes that got more space allocated.
-        *
-        * We don't need to actively wait for the update here, next vblank
-        * will just get more DDB space with the correct WM values.
-        */
-       for_each_intel_crtc(dev, crtc) {
-               if (!crtc->active)
-                       continue;
-
-               pipe = crtc->pipe;
-
-               /*
-                * At this point, only the pipes more space than before are
-                * left to re-allocate.
-                */
-               if (reallocated[pipe])
-                       continue;
-
-               skl_wm_flush_pipe(dev_priv, pipe, 3);
-       }
+       return false;
 }
 
 static int skl_update_pipe_wm(struct drm_crtc_state *cstate,
        struct skl_wm_values *hw_vals = &dev_priv->wm.skl_hw;
        struct intel_crtc_state *cstate = to_intel_crtc_state(crtc->state);
        struct skl_pipe_wm *pipe_wm = &cstate->wm.skl.optimal;
-       int pipe;
+       enum pipe pipe = intel_crtc->pipe;
 
        if ((results->dirty_pipes & drm_crtc_mask(crtc)) == 0)
                return;
 
        mutex_lock(&dev_priv->wm.wm_mutex);
 
-       skl_write_wm_values(dev_priv, results);
-       skl_flush_wm_values(dev_priv, results);
-
        /*
-        * Store the new configuration (but only for the pipes that have
-        * changed; the other values weren't recomputed).
+        * If this pipe isn't active already, we're going to be enabling it
+        * very soon. Since it's safe to update a pipe's ddb allocation while
+        * the pipe's shut off, just do so here. Already active pipes will have
+        * their watermarks updated once we update their planes.
         */
-       for_each_pipe_masked(dev_priv, pipe, results->dirty_pipes)
-               skl_copy_wm_for_pipe(hw_vals, results, pipe);
+       if (crtc->state->active_changed) {
+               int plane;
+
+               for (plane = 0; plane < intel_num_planes(intel_crtc); plane++)
+                       skl_write_plane_wm(intel_crtc, results, plane);
+
+               skl_write_cursor_wm(intel_crtc, results);
+       }
+
+       skl_copy_wm_for_pipe(hw_vals, results, pipe);
 
        mutex_unlock(&dev_priv->wm.wm_mutex);
 }