drm/i915/gen9: implement missing case for SKL watermarks calculation

This should affect linear and X tiled planes on really small htotal
cases. It doesn't seem to be a very feasible case, but let's implement
it since it's on the specification and it's better to have it and
never need than not have it and realize we needed it.

Reviewed-by: Lyude <cpaul@redhat.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1474578035-424-9-git-send-email-paulo.r.zanoni@intel.com

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index fd7465c..d5e7738 100644 (file)
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3615,7 +3615,10 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
            fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
                selected_result = max(method2, y_tile_minimum);
        } else {
-               if ((ddb_allocation / plane_blocks_per_line) >= 1)
+               if ((cpp * cstate->base.adjusted_mode.crtc_htotal / 512 < 1) &&
+                   (plane_bytes_per_line / 512 < 1))
+                       selected_result = method2;
+               else if ((ddb_allocation / plane_blocks_per_line) >= 1)
                        selected_result = min(method1, method2);
                else
                        selected_result = method1;