[Intel-gfx] [PATCH] drm/i915: Implement vblank synchronized MBUS join changes

[Stanislav Lisovskiy]

Currently we can't change MBUS join status without doing a modeset,
because we are lacking mechanism to synchronize those with vblank.
However then this means that we can't do a fastset, if there is a need
to change MBUS join state. Fix that by implementing such change.
We already call correspondent check and update at pre_plane dbuf update,
so the only thing left is to have a non-modeset version of that.
If active pipes stay the same then fastset is possible and only MBUS
join state/ddb allocation updates would be committed.

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
---
 drivers/gpu/drm/i915/display/skl_watermark.c | 25 ++++++++++++++------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c b/drivers/gpu/drm/i915/display/skl_watermark.c
index 063929a42a42f..19840e6d7318c 100644
--- a/drivers/gpu/drm/i915/display/skl_watermark.c
+++ b/drivers/gpu/drm/i915/display/skl_watermark.c
@@ -2614,13 +2614,6 @@ skl_compute_ddb(struct intel_atomic_state *state)
 		if (ret)
 			return ret;
 
-		if (old_dbuf_state->joined_mbus != new_dbuf_state->joined_mbus) {
-			/* TODO: Implement vblank synchronized MBUS joining changes */
-			ret = intel_modeset_all_pipes(state, "MBUS joining change");
-			if (ret)
-				return ret;
-		}
-
 		drm_dbg_kms(&i915->drm,
 			    "Enabled dbuf slices 0x%x -> 0x%x (total dbuf slices 0x%x), mbus joined? %s->%s\n",
 			    old_dbuf_state->enabled_slices,
@@ -3524,6 +3517,24 @@ void intel_dbuf_pre_plane_update(struct intel_atomic_state *state)
 
 	WARN_ON(!new_dbuf_state->base.changed);
 
+	/*
+	 * If we are not doing a modeset, that means we must synchronize
+	 * our MBUS configuration changes with vblank for all active crtcs.
+	 */
+	if (!state->modeset) {
+		struct intel_crtc *crtc;
+		struct intel_crtc_state *new_crtc_state;
+		int i;
+
+		for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
+
+			if (!new_crtc_state->hw.active)
+				continue;
+
+			intel_crtc_wait_for_next_vblank(crtc);
+		}
+	}
+
 	update_mbus_pre_enable(state);
 	gen9_dbuf_slices_update(i915,
 				old_dbuf_state->enabled_slices |
-- 
2.37.3