[Intel-gfx] [PATCH 26/29] drm/i915/dp_mst: Force modeset CRTC if DSC toggling requires it

[Imre Deak]

Enabling / disabling DSC decompression in the branch device downstream
of the source may reset the while branch device. To avoid this while the
streams are still active, force a modeset on all CRTC/ports connected to
this branch device.

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c |  4 ++
 drivers/gpu/drm/i915/display/intel_dp_mst.c  | 72 ++++++++++++++++++++
 drivers/gpu/drm/i915/display/intel_dp_mst.h  |  2 +
 3 files changed, 78 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 22f88389035bd..a33e5bbf5165a 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -6490,6 +6490,10 @@ int intel_atomic_check(struct drm_device *dev,
 		if (!new_crtc_state->hw.enable || intel_crtc_needs_modeset(new_crtc_state))
 			continue;
 
+		if (intel_dp_mst_crtc_needs_modeset(state, crtc))
+			intel_modeset_pipes_in_mask_early(state, "MST topology",
+							  BIT(crtc->pipe));
+
 		if (intel_dp_mst_is_slave_trans(new_crtc_state)) {
 			enum transcoder master = new_crtc_state->mst_master_transcoder;
 
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 9f4894c2e7860..d4dcfb2c09b2a 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -1606,3 +1606,75 @@ int intel_dp_mst_add_topology_state_for_crtc(struct intel_atomic_state *state,
 
 	return 0;
 }
+
+static struct intel_connector *
+get_connector_in_state_for_crtc(struct intel_atomic_state *state,
+				const struct intel_crtc *crtc)
+{
+	struct drm_connector_state *old_conn_state;
+	struct drm_connector_state *new_conn_state;
+	struct drm_connector *_connector;
+	int i;
+
+	for_each_oldnew_connector_in_state(&state->base, _connector,
+					   old_conn_state, new_conn_state, i) {
+		struct intel_connector *connector =
+			to_intel_connector(_connector);
+
+		if (old_conn_state->crtc == &crtc->base ||
+		    new_conn_state->crtc == &crtc->base)
+			return connector;
+	}
+
+	return NULL;
+}
+
+bool intel_dp_mst_crtc_needs_modeset(struct intel_atomic_state *state,
+				     struct intel_crtc *crtc)
+{
+	const struct intel_connector *crtc_connector;
+	const struct drm_connector_state *conn_state;
+	const struct drm_connector *_connector;
+	int i;
+
+	if (!intel_crtc_has_type(intel_atomic_get_new_crtc_state(state, crtc),
+				 INTEL_OUTPUT_DP_MST))
+		return false;
+
+	crtc_connector = get_connector_in_state_for_crtc(state, crtc);
+
+	if (!crtc_connector)
+		/* None of the connectors in the topology needs modeset */
+		return false;
+
+	for_each_new_connector_in_state(&state->base, _connector, conn_state, i) {
+		const struct intel_connector *connector =
+			to_intel_connector(_connector);
+		const struct intel_crtc_state *new_crtc_state =
+			intel_atomic_get_new_crtc_state(state, crtc);
+		const struct intel_crtc_state *old_crtc_state =
+			intel_atomic_get_old_crtc_state(state, crtc);
+
+		if (connector->mst_port != crtc_connector->mst_port)
+			continue;
+
+		if (!intel_crtc_needs_modeset(new_crtc_state))
+			continue;
+
+		if (old_crtc_state->dsc.compression_enable ==
+		    new_crtc_state->dsc.compression_enable)
+			continue;
+
+		/*
+		 * Toggling the compression flag because of this stream in the first
+		 * downstream branch device's UFP DPCD may reset the whole branch
+		 * device. To avoid the reset while other streams are also
+		 * active modeset the whole MST topology in this case.
+		 */
+		if (connector->dp.dsc_decompression_aux ==
+		    &connector->mst_port->aux)
+			return true;
+	}
+
+	return false;
+}
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.h b/drivers/gpu/drm/i915/display/intel_dp_mst.h
index f1815bb722672..fc5e85776a858 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.h
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.h
@@ -22,5 +22,7 @@ bool intel_dp_mst_is_slave_trans(const struct intel_crtc_state *crtc_state);
 bool intel_dp_mst_source_support(struct intel_dp *intel_dp);
 int intel_dp_mst_add_topology_state_for_crtc(struct intel_atomic_state *state,
 					     struct intel_crtc *crtc);
+bool intel_dp_mst_crtc_needs_modeset(struct intel_atomic_state *state,
+				     struct intel_crtc *crtc);
 
 #endif /* __INTEL_DP_MST_H__ */
-- 
2.39.2