drm/i915/skl+: nv12 workaround disable WM level 1-7

Display Workaround #0826 (SKL:ALL BXT:ALL) & #1059(CNL:A)
Hardware sometimes fails to wake memory from pkg C states fetching the
last few lines of planar YUV 420 (NV12) planes. This causes
intermittent underflow and corruption.
WA: Disable package C states or do not enable latency levels 1 through 7
(WM1 - WM7) on NV12 planes.

v2: Addressed review comments by Maarten.

v3: Adding reviewed by tag from Shashank Sharma

v4: Added reviewed by from Juha-Pekka Heikkila

v5: Rebased the series
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Signed-off-by: Vidya Srinivas <vidya.srinivas@intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1523245273-30264-9-git-send-email-vidya.srinivas@intel.com

drivers/gpu/drm/i915/intel_pm.c

@@ -4653,6 +4653,17 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 		}
 	}
 
+	/*
+	 * Display WA #826 (SKL:ALL, BXT:ALL) & #1059 (CNL:A)
+	 * disable wm level 1-7 on NV12 planes
+	 */
+	if (wp->is_planar && level >= 1 &&
+	    (IS_SKYLAKE(dev_priv) || IS_BROXTON(dev_priv) ||
+	     IS_CNL_REVID(dev_priv, CNL_REVID_A0, CNL_REVID_A0))) {
+		result->plane_en = false;
+		return 0;
+	}
+
 	/* The number of lines are ignored for the level 0 watermark. */
 	result->plane_res_b = res_blocks;
 	result->plane_res_l = res_lines;