[Intel-gfx] [PATCH] drm/i915: Fix ilk+ watermarks when disabling pipes

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

We're no longer programming any watermarks when we're disabling
a pipe. That means ilk_wm_merge() & co. will keep considering
the any pipe that is getting disabled as still enabled. Thus we
either get no LP1+ watermakrs (ilk-ivb), or we get suboptimal
ones (hsw-bdw).

This seems to have been broken by commit b6b178a77210 ("drm/i915:
Calculate ironlake intermediate watermarks correctly, v2."). Before
that we apparently had some difference between the intermediate
and optimal watermarks and so we would program the optiomal ones.
Now intermediate and optimal are identical for disabled pipes
and so we don't program either.

Fix this by programming the intermediate watermarks even for
disabled pipes. We were already doing that for skl+. We'll
leave out gmch platforms for now since those do the merging
in a different manner and should work as is. We'll want to
unify this eventually, but play it safe for now and just put
in a FIXME.

Cc: stable at vger.kernel.org
Cc: Matt Roper <matthew.d.roper at intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Fixes: b6b178a77210 ("drm/i915: Calculate ironlake intermediate watermarks correctly, v2.")
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index fe045abb6472..1e963dcebf2d 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -12818,17 +12818,12 @@ static void intel_atomic_commit_tail(struct drm_atomic_state *state)
 			intel_check_cpu_fifo_underruns(dev_priv);
 			intel_check_pch_fifo_underruns(dev_priv);
 
-			if (!new_crtc_state->active) {
-				/*
-				 * Make sure we don't call initial_watermarks
-				 * for ILK-style watermark updates.
-				 *
-				 * No clue what this is supposed to achieve.
-				 */
-				if (INTEL_GEN(dev_priv) >= 9)
-					dev_priv->display.initial_watermarks(intel_state,
-									     new_intel_crtc_state);
-			}
+			/* FIXME unify this for all platforms */
+			if (!new_crtc_state->active &&
+			    !HAS_GMCH_DISPLAY(dev_priv) &&
+			    dev_priv->display.initial_watermarks)
+				dev_priv->display.initial_watermarks(intel_state,
+								     new_intel_crtc_state);
 		}
 	}
 
-- 
2.18.1