drm/i915: don't apply Display WAs 1125 and 1126 to GLK/CNL+

BSpec does not show these WAs as applicable to GLK, and for CNL it
only shows them applicable for a super early pre-production stepping
we shouldn't be caring about anymore. Remove these so we can avoid
them on ICL too.

v2: Change how we check for gen9 display platforms (Ville).

Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181114012432.21809-1-paulo.r.zanoni@intel.com

drivers/gpu/drm/i915/intel_pm.c

@@ -4730,28 +4730,31 @@ static void skl_compute_plane_wm(const struct intel_crtc_state *cstate,
 	res_lines = div_round_up_fixed16(selected_result,
 					 wp->plane_blocks_per_line);
 
-	/* Display WA #1125: skl,bxt,kbl,glk */
-	if (level == 0 && wp->rc_surface)
-		res_blocks += fixed16_to_u32_round_up(wp->y_tile_minimum);
-
-	/* Display WA #1126: skl,bxt,kbl,glk */
-	if (level >= 1 && level <= 7) {
-		if (wp->y_tiled) {
-			res_blocks += fixed16_to_u32_round_up(
-							wp->y_tile_minimum);
-			res_lines += wp->y_min_scanlines;
-		} else {
-			res_blocks++;
-		}
+	if (IS_GEN9_BC(dev_priv) || IS_BROXTON(dev_priv)) {
+		/* Display WA #1125: skl,bxt,kbl */
+		if (level == 0 && wp->rc_surface)
+			res_blocks +=
+				fixed16_to_u32_round_up(wp->y_tile_minimum);
+
+		/* Display WA #1126: skl,bxt,kbl */
+		if (level >= 1 && level <= 7) {
+			if (wp->y_tiled) {
+				res_blocks +=
+				    fixed16_to_u32_round_up(wp->y_tile_minimum);
+				res_lines += wp->y_min_scanlines;
+			} else {
+				res_blocks++;
+			}
 
-		/*
-		 * Make sure result blocks for higher latency levels are atleast
-		 * as high as level below the current level.
-		 * Assumption in DDB algorithm optimization for special cases.
-		 * Also covers Display WA #1125 for RC.
-		 */
-		if (result_prev->plane_res_b > res_blocks)
-			res_blocks = result_prev->plane_res_b;
+			/*
+			 * Make sure result blocks for higher latency levels are
+			 * atleast as high as level below the current level.
+			 * Assumption in DDB algorithm optimization for special
+			 * cases. Also covers Display WA #1125 for RC.
+			 */
+			if (result_prev->plane_res_b > res_blocks)
+				res_blocks = result_prev->plane_res_b;
+		}
 	}
 
 	/* The number of lines are ignored for the level 0 watermark. */