[Intel-gfx] [PATCH 3/5] drm/i915/tgl: do not enable transcoder clock twice on MST

[Lucas De Marchi]

For MST on Tiger Lake there are different moments when we need to
configure the transcoder clock select. For the first link this is in step
7.a of the spec, before training the link.  For additional streams this
should be done as part of step 8.b after programming receiver VC Payload
ID.

Bspec: 49190

Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
---
 drivers/gpu/drm/i915/display/intel_ddi.c    |  7 ++++---
 drivers/gpu/drm/i915/display/intel_dp_mst.c | 16 +++++++++++++---
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index fed7fc56dd92..2ce998529d08 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -3462,9 +3462,10 @@ static void tgl_ddi_pre_enable_dp(struct intel_encoder *encoder,
 	icl_program_mg_dp_mode(dig_port, crtc_state);
 
 	/*
-	 * 7.a - Steps in this function should only be executed over MST
-	 * master, what will be taken in care by MST hook
-	 * intel_mst_pre_enable_dp()
+	 * 7.a - single stream or multi-stream master transcoder: Configure
+	 * Transcoder Clock Select. For additional MST streams this will be done
+	 * by intel_mst_pre_enable_dp() after programming VC Payload ID through
+	 * AUX.
 	 */
 	intel_ddi_enable_pipe_clock(crtc_state);
 
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index a9962846a503..ad54618f6142 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -299,21 +299,23 @@ static void intel_mst_pre_enable_dp(struct intel_encoder *encoder,
 		to_intel_connector(conn_state->connector);
 	int ret;
 	u32 temp;
+	bool first_mst_stream;
 
 	/* MST encoders are bound to a crtc, not to a connector,
 	 * force the mapping here for get_hw_state.
 	 */
 	connector->encoder = encoder;
 	intel_mst->connector = connector;
+	first_mst_stream = intel_dp->active_mst_links == 0;
 
 	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
 
-	if (intel_dp->active_mst_links == 0)
+	if (first_mst_stream)
 		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
 
 	drm_dp_send_power_updown_phy(&intel_dp->mst_mgr, connector->port, true);
 
-	if (intel_dp->active_mst_links == 0)
+	if (first_mst_stream)
 		intel_dig_port->base.pre_enable(&intel_dig_port->base,
 						pipe_config, NULL);
 
@@ -330,7 +332,15 @@ static void intel_mst_pre_enable_dp(struct intel_encoder *encoder,
 
 	ret = drm_dp_update_payload_part1(&intel_dp->mst_mgr);
 
-	intel_ddi_enable_pipe_clock(pipe_config);
+	/*
+	 * Before Gen 12 this is not done as part of
+	 * intel_dig_port->base.pre_enable() and should be done here. For
+	 * Gen 12+ the step in which this should be done is different for the
+	 * first MST stream, so it's done on the DDI for the first stream and
+	 * here for the following ones.
+	 */
+	if (INTEL_GEN(dev_priv) < 12 || !first_mst_stream)
+		intel_ddi_enable_pipe_clock(pipe_config);
 }
 
 static void intel_mst_enable_dp(struct intel_encoder *encoder,
-- 
2.23.0