[PATCH] drm/i915: Make legacy cursor updates more unsynced

[ville.syrjala@linux.intel.com]

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

We're clearing the legacy_cursor_update flag before calling
drm_atomic_helper_setup_commit() which means the helper will
wait for the flip to complete before cleaning up the framebuffers.
That's not what we want for the legacy cursor, so let's clear
the flag after setting up the commit.

Also toss in a FIXME about solving these problems in a nicer
way using the fabled vblank workers.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Uwe Kleine-König <uwe@kleine-koenig.org>
Cc: Rafael Ristovski <rafael.ristovski@gmail.com>
Fixes: a5509abda48e ("drm/i915: Fix legacy cursor vs. watermarks for ILK-BDW")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 654b8a0c28ee..05ff193f2dd8 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -13024,6 +13024,10 @@ static int intel_atomic_commit(struct drm_device *dev,
 	struct drm_i915_private *dev_priv = to_i915(dev);
 	int ret = 0;
 
+	ret = drm_atomic_helper_setup_commit(state, nonblock);
+	if (ret)
+		return ret;
+
 	/*
 	 * The intel_legacy_cursor_update() fast path takes care
 	 * of avoiding the vblank waits for simple cursor
@@ -13031,14 +13035,18 @@ static int intel_atomic_commit(struct drm_device *dev,
 	 * we want to perform the vblank waits so that watermark
 	 * updates happen during the correct frames. Gen9+ have
 	 * double buffered watermarks and so shouldn't need this.
+	 *
+	 * Do this after drm_atomic_helper_setup_commit() because
+	 * we still want to skip the fb cleanup waits from the
+	 * atomic helper. Although that does risk yanking the
+	 * mapping from under the display engine.
+	 *
+	 * FIXME doing watermarks and fb cleanup from a vblank worker
+	 * (assuming we had any) would solve these problems.
 	 */
 	if (INTEL_GEN(dev_priv) < 9)
 		state->legacy_cursor_update = false;
 
-	ret = drm_atomic_helper_setup_commit(state, nonblock);
-	if (ret)
-		return ret;
-
 	drm_atomic_state_get(state);
 	i915_sw_fence_init(&intel_state->commit_ready,
 			   intel_atomic_commit_ready);
-- 
2.10.2

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