drm/i915/gen9: Propagate watermark calculation failures up the call chain

Once we move watermark calculation to the atomic check phase, we'll want
to start rejecting display configurations that exceed out watermark
limits.  At the moment we just assume that there's always a valid set of
watermarks, even though this may not actually be true.  Let's prepare by
passing return codes up through the call stack in preparation.
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463061971-19638-15-git-send-email-matthew.d.roper@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -13309,7 +13309,7 @@ static int intel_modeset_checks(struct drm_atomic_state *state)
  * phase.  The code here should be run after the per-crtc and per-plane 'check'
  * handlers to ensure that all derived state has been updated.
  */
-static void calc_watermark_data(struct drm_atomic_state *state)
+static int calc_watermark_data(struct drm_atomic_state *state)
 {
 	struct drm_device *dev = state->dev;
 	struct drm_i915_private *dev_priv = to_i915(dev);
@@ -13345,7 +13345,9 @@ static void calc_watermark_data(struct drm_atomic_state *state)
 
 	/* Is there platform-specific watermark information to calculate? */
 	if (dev_priv->display.compute_global_watermarks)
-		dev_priv->display.compute_global_watermarks(state);
+		return dev_priv->display.compute_global_watermarks(state);
+
+	return 0;
 }
 
 /**
@@ -13432,9 +13434,7 @@ static int intel_atomic_check(struct drm_device *dev,
 		return ret;
 
 	intel_fbc_choose_crtc(dev_priv, state);
-	calc_watermark_data(state);
-
-	return 0;
+	return calc_watermark_data(state);
 }
 
 static int intel_atomic_prepare_commit(struct drm_device *dev,

drivers/gpu/drm/i915/intel_pm.c

@@ -3238,13 +3238,14 @@ static bool skl_ddb_allocation_changed(const struct skl_ddb_allocation *new_ddb,
 	return false;
 }
 
-static bool skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
+static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 				struct intel_crtc_state *cstate,
 				struct intel_plane_state *intel_pstate,
 				uint16_t ddb_allocation,
 				int level,
 				uint16_t *out_blocks, /* out */
-				 uint8_t *out_lines /* out */)
+				uint8_t *out_lines, /* out */
+				bool *enabled /* out */)
 {
 	struct drm_plane_state *pstate = &intel_pstate->base;
 	struct drm_framebuffer *fb = pstate->fb;
@@ -3256,8 +3257,10 @@ static bool skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 	uint8_t cpp;
 	uint32_t width = 0, height = 0;
 
-	if (latency == 0 || !cstate->base.active || !intel_pstate->visible)
-		return false;
+	if (latency == 0 || !cstate->base.active || !intel_pstate->visible) {
+		*enabled = false;
+		return 0;
+	}
 
 	width = drm_rect_width(&intel_pstate->src) >> 16;
 	height = drm_rect_height(&intel_pstate->src) >> 16;
@@ -3318,13 +3321,16 @@ static bool skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 			res_blocks++;
 	}
 
-	if (res_blocks >= ddb_allocation || res_lines > 31)
-		return false;
+	if (res_blocks >= ddb_allocation || res_lines > 31) {
+		*enabled = false;
+		return 0;
+	}
 
 	*out_blocks = res_blocks;
 	*out_lines = res_lines;
+	*enabled = true;
 
-	return true;
+	return 0;
 }
 
 static int
@@ -3342,6 +3348,7 @@ skl_compute_wm_level(const struct drm_i915_private *dev_priv,
 	struct intel_plane_state *intel_pstate;
 	uint16_t ddb_blocks;
 	enum pipe pipe = intel_crtc->pipe;
+	int ret;
 
 	/*
 	 * We'll only calculate watermarks for planes that are actually
@@ -3379,13 +3386,16 @@ skl_compute_wm_level(const struct drm_i915_private *dev_priv,
 
 		ddb_blocks = skl_ddb_entry_size(&ddb->plane[pipe][i]);
 
-		result->plane_en[i] = skl_compute_plane_wm(dev_priv,
+		ret = skl_compute_plane_wm(dev_priv,
 					   cstate,
 					   intel_pstate,
 					   ddb_blocks,
 					   level,
 					   &result->plane_res_b[i],
-						&result->plane_res_l[i]);
+					   &result->plane_res_l[i],
+					   &result->plane_en[i]);
+		if (ret)
+			return ret;
 	}
 
 	return 0;
@@ -3422,21 +3432,26 @@ static void skl_compute_transition_wm(struct intel_crtc_state *cstate,
 	}
 }
 
-static void skl_build_pipe_wm(struct intel_crtc_state *cstate,
+static int skl_build_pipe_wm(struct intel_crtc_state *cstate,
 			     struct skl_ddb_allocation *ddb,
 			     struct skl_pipe_wm *pipe_wm)
 {
 	struct drm_device *dev = cstate->base.crtc->dev;
 	const struct drm_i915_private *dev_priv = dev->dev_private;
 	int level, max_level = ilk_wm_max_level(dev);
+	int ret;
 
 	for (level = 0; level <= max_level; level++) {
-		skl_compute_wm_level(dev_priv, ddb, cstate,
+		ret = skl_compute_wm_level(dev_priv, ddb, cstate,
 					   level, &pipe_wm->wm[level]);
+		if (ret)
+			return ret;
 	}
 	pipe_wm->linetime = skl_compute_linetime_wm(cstate);
 
 	skl_compute_transition_wm(cstate, &pipe_wm->trans_wm);
+
+	return 0;
 }
 
 static void skl_compute_wm_results(struct drm_device *dev,
@@ -3683,21 +3698,27 @@ static void skl_flush_wm_values(struct drm_i915_private *dev_priv,
 	}
 }
 
-static bool skl_update_pipe_wm(struct drm_crtc_state *cstate,
+static int skl_update_pipe_wm(struct drm_crtc_state *cstate,
 			      struct skl_ddb_allocation *ddb, /* out */
-			       struct skl_pipe_wm *pipe_wm /* out */)
+			      struct skl_pipe_wm *pipe_wm, /* out */
+			      bool *changed /* out */)
 {
 	struct intel_crtc *intel_crtc = to_intel_crtc(cstate->crtc);
 	struct intel_crtc_state *intel_cstate = to_intel_crtc_state(cstate);
+	int ret;
 
-	skl_build_pipe_wm(intel_cstate, ddb, pipe_wm);
+	ret = skl_build_pipe_wm(intel_cstate, ddb, pipe_wm);
+	if (ret)
+		return ret;
 
 	if (!memcmp(&intel_crtc->wm.active.skl, pipe_wm, sizeof(*pipe_wm)))
-		return false;
+		*changed = false;
+	else
+		*changed = true;
 
 	intel_crtc->wm.active.skl = *pipe_wm;
 
-	return true;
+	return 0;
 }
 
 static void skl_update_other_pipe_wm(struct drm_device *dev,
@@ -3730,8 +3751,8 @@ static void skl_update_other_pipe_wm(struct drm_device *dev,
 		if (!intel_crtc->active)
 			continue;
 
-		wm_changed = skl_update_pipe_wm(intel_crtc->base.state,
-						&r->ddb, &pipe_wm);
+		skl_update_pipe_wm(intel_crtc->base.state,
+				   &r->ddb, &pipe_wm, &wm_changed);
 
 		/*
 		 * If we end up re-computing the other pipe WM values, it's
@@ -3841,14 +3862,15 @@ static void skl_update_wm(struct drm_crtc *crtc)
 	struct skl_wm_values *results = &dev_priv->wm.skl_results;
 	struct intel_crtc_state *cstate = to_intel_crtc_state(crtc->state);
 	struct skl_pipe_wm *pipe_wm = &cstate->wm.skl.optimal;
-
+	bool wm_changed;
 
 	/* Clear all dirty flags */
 	results->dirty_pipes = 0;
 
 	skl_clear_wm(results, intel_crtc->pipe);
 
-	if (!skl_update_pipe_wm(crtc->state, &results->ddb, pipe_wm))
+	skl_update_pipe_wm(crtc->state, &results->ddb, pipe_wm, &wm_changed);
+	if (!wm_changed)
 		return;
 
 	skl_compute_wm_results(dev, pipe_wm, results, intel_crtc);