[Intel-gfx] [PATCH 8/9] drm/i915/gen9: implement missing case for SKL watermarks calculation

[Paulo Zanoni]

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 at redhat.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 2e6099b..9edc8ce 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3624,7 +3624,10 @@ 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;
-- 
2.7.4