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
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 14c2c3e..1d8407a 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3238,13 +3238,14 @@
 	return false;
 }
 
-static bool 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 */)
+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 */
+				bool *enabled /* out */)
 {
 	struct drm_plane_state *pstate = &intel_pstate->base;
 	struct drm_framebuffer *fb = pstate->fb;
@@ -3256,8 +3257,10 @@
 	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 @@
 			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 @@
 	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 @@
 
 		ddb_blocks = skl_ddb_entry_size(&ddb->plane[pipe][i]);
 
-		result->plane_en[i] = skl_compute_plane_wm(dev_priv,
-						cstate,
-						intel_pstate,
-						ddb_blocks,
-						level,
-						&result->plane_res_b[i],
-						&result->plane_res_l[i]);
+		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_en[i]);
+		if (ret)
+			return ret;
 	}
 
 	return 0;
@@ -3422,21 +3432,26 @@
 	}
 }
 
-static void skl_build_pipe_wm(struct intel_crtc_state *cstate,
-			      struct skl_ddb_allocation *ddb,
-			      struct skl_pipe_wm *pipe_wm)
+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,
-				     level, &pipe_wm->wm[level]);
+		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 bool skl_update_pipe_wm(struct drm_crtc_state *cstate,
-			       struct skl_ddb_allocation *ddb, /* out */
-			       struct skl_pipe_wm *pipe_wm /* out */)
+static int skl_update_pipe_wm(struct drm_crtc_state *cstate,
+			      struct skl_ddb_allocation *ddb, /* 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 @@
 		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 @@
 	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);