drm/i915: Account for minimum ddb allocation restrictions

On icl+ bspec tells us to calculate a separate minimum ddb
allocation from the blocks watermark. Both have to be checked
against the actual ddb allocation, but since we do things the
other way around we'll just calculat the minimum acceptable
ddb allocation by taking the maximum of the two values.

We'll also replace the memcmp() with a full trawl over the
the watermarks so that it'll ignore the min_ddb_alloc
because we can't directly read that out from the hw. I suppose
we could reconstruct it from the other values, but I was
too lazy to do that now.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181221171436.8218-6-ville.syrjala@linux.intel.com
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -1114,6 +1114,7 @@ struct skl_ddb_values {
 };
 
 struct skl_wm_level {
+	u16 min_ddb_alloc;
 	u16 plane_res_b;
 	u8 plane_res_l;
 	bool plane_en;

drivers/gpu/drm/i915/intel_pm.c

@@ -4371,8 +4371,8 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
 				continue;
 
 			wm = &cstate->wm.skl.optimal.planes[plane_id];
-			blocks += wm->wm[level].plane_res_b + 1;
-			blocks += wm->uv_wm[level].plane_res_b + 1;
+			blocks += wm->wm[level].min_ddb_alloc;
+			blocks += wm->uv_wm[level].min_ddb_alloc;
 		}
 
 		if (blocks < alloc_size) {
@@ -4413,7 +4413,7 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
 		extra = min_t(u16, alloc_size,
 			      DIV64_U64_ROUND_UP(alloc_size * rate,
 						 total_data_rate));
-		total[plane_id] = wm->wm[level].plane_res_b + 1 + extra;
+		total[plane_id] = wm->wm[level].min_ddb_alloc + extra;
 		alloc_size -= extra;
 		total_data_rate -= rate;
 
@@ -4424,7 +4424,7 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
 		extra = min_t(u16, alloc_size,
 			      DIV64_U64_ROUND_UP(alloc_size * rate,
 						 total_data_rate));
-		uv_total[plane_id] = wm->uv_wm[level].plane_res_b + 1 + extra;
+		uv_total[plane_id] = wm->uv_wm[level].min_ddb_alloc + extra;
 		alloc_size -= extra;
 		total_data_rate -= rate;
 	}
@@ -4695,7 +4695,7 @@ static void skl_compute_plane_wm(const struct intel_crtc_state *cstate,
 	u32 latency = dev_priv->wm.skl_latency[level];
 	uint_fixed_16_16_t method1, method2;
 	uint_fixed_16_16_t selected_result;
-	u32 res_blocks, res_lines;
+	u32 res_blocks, res_lines, min_ddb_alloc = 0;
 	struct intel_atomic_state *state =
 		to_intel_atomic_state(cstate->base.state);
 	bool apply_memory_bw_wa = skl_needs_memory_bw_wa(state);
@@ -4768,6 +4768,24 @@ static void skl_compute_plane_wm(const struct intel_crtc_state *cstate,
 		}
 	}
 
+	if (INTEL_GEN(dev_priv) >= 11) {
+		if (wp->y_tiled) {
+			int extra_lines;
+
+			if (res_lines % wp->y_min_scanlines == 0)
+				extra_lines = wp->y_min_scanlines;
+			else
+				extra_lines = wp->y_min_scanlines * 2 -
+					res_lines % wp->y_min_scanlines;
+
+			min_ddb_alloc = mul_round_up_u32_fixed16(res_lines + extra_lines,
+								 wp->plane_blocks_per_line);
+		} else {
+			min_ddb_alloc = res_blocks +
+				DIV_ROUND_UP(res_blocks, 10);
+		}
+	}
+
 	if (!skl_wm_has_lines(dev_priv, level))
 		res_lines = 0;
 
@@ -4782,6 +4800,8 @@ static void skl_compute_plane_wm(const struct intel_crtc_state *cstate,
 	 */
 	result->plane_res_b = res_blocks;
 	result->plane_res_l = res_lines;
+	/* Bspec says: value >= plane ddb allocation -> invalid, hence the +1 here */
+	result->min_ddb_alloc = max(min_ddb_alloc, res_blocks) + 1;
 	result->plane_en = true;
 }
 
@@ -5132,6 +5152,23 @@ static bool skl_plane_wm_equals(struct drm_i915_private *dev_priv,
 	return skl_wm_level_equals(&wm1->trans_wm, &wm2->trans_wm);
 }
 
+static bool skl_pipe_wm_equals(struct intel_crtc *crtc,
+			       const struct skl_pipe_wm *wm1,
+			       const struct skl_pipe_wm *wm2)
+{
+	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
+	enum plane_id plane_id;
+
+	for_each_plane_id_on_crtc(crtc, plane_id) {
+		if (!skl_plane_wm_equals(dev_priv,
+					 &wm1->planes[plane_id],
+					 &wm2->planes[plane_id]))
+			return false;
+	}
+
+	return wm1->linetime == wm2->linetime;
+}
+
 static inline bool skl_ddb_entries_overlap(const struct skl_ddb_entry *a,
 					   const struct skl_ddb_entry *b)
 {
@@ -5158,16 +5195,14 @@ static int skl_update_pipe_wm(struct intel_crtc_state *cstate,
 			      struct skl_pipe_wm *pipe_wm, /* out */
 			      bool *changed /* out */)
 {
+	struct intel_crtc *crtc = to_intel_crtc(cstate->base.crtc);
 	int ret;
 
 	ret = skl_build_pipe_wm(cstate, pipe_wm);
 	if (ret)
 		return ret;
 
-	if (!memcmp(old_pipe_wm, pipe_wm, sizeof(*pipe_wm)))
-		*changed = false;
-	else
-		*changed = true;
+	*changed = !skl_pipe_wm_equals(crtc, old_pipe_wm, pipe_wm);
 
 	return 0;
 }