diff mbox series

[v4,21/30] drm/i915/dp_mst: Handle the Synaptics HBlank expansion quirk

Message ID 20231030155843.2251023-22-imre.deak@intel.com (mailing list archive)
State New, archived
Headers show
Series drm/i915: Improve BW management on MST links | expand

Commit Message

Imre Deak Oct. 30, 2023, 3:58 p.m. UTC 
The Synaptics MST hubs expose some sink EDID modes with a reduced HBLANK
period, presumedly to save BW, which the hub expands before forwarding
the stream to the sink. In particular a 4k mode with a standard CVT
HBLANK period is exposed with either a CVT reduced blank RBv1,v2 (80,
160 pixel) or a non-CVT 56 pixel HBLANK period. The DP standard
describes the above HBLANK expansion functionality, but it requires
enabling this explicitly, whereas these hubs apply the expansion
transparently.

Such modes will work okay until DSC decompression is enabled in the hub
for the given sink, but after this the same mode will not work reliably
in decompressed mode. As a workaround force enable DSC for such modes.
Apply the WA when the HBLANK period is 300ns or below, matching the
above tested modes with a 533.25MHz dotclock and maximum 160 HBLANK
pixels.

OTOH DSC for these modes will only work above a certain compressed bpp
threshold which depends on the link rate, so apply this limit as well
in the workaround.

Apply the workaround only for Synaptics hubs which support the HBLANK
expansion.

v2:
- Apply the WA whenever the HBLANK period is 300ns or below.

Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com> (v1)
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 .../drm/i915/display/intel_display_types.h    |   2 +
 drivers/gpu/drm/i915/display/intel_dp_mst.c   | 119 +++++++++++++++++-
 2 files changed, 117 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 65ea37fe8cff3..409dbf8a2a1cd 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -624,6 +624,8 @@  struct intel_connector {
 		struct drm_dp_aux *dsc_decompression_aux;
 		u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE];
 		u8 fec_capability;
+
+		u8 dsc_hblank_expansion_quirk:1;
 	} dp;
 
 	/* Work struct to schedule a uevent on link train failure */
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 191d45cddd498..94627ab271c7d 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -360,8 +360,77 @@  static int intel_dp_mst_update_slots(struct intel_encoder *encoder,
 	return 0;
 }
 
+static int mode_hblank_period_ns(const struct drm_display_mode *mode)
+{
+	return DIV_ROUND_CLOSEST_ULL(mul_u32_u32(mode->htotal - mode->hdisplay,
+						 NSEC_PER_SEC / 1000),
+				     mode->crtc_clock);
+}
+
+static bool
+hblank_expansion_quirk_needs_dsc(const struct intel_connector *connector,
+				 const struct intel_crtc_state *crtc_state)
+{
+	const struct drm_display_mode *adjusted_mode =
+		&crtc_state->hw.adjusted_mode;
+
+	if (!connector->dp.dsc_hblank_expansion_quirk)
+		return false;
+
+	if (mode_hblank_period_ns(adjusted_mode) > 300)
+		return false;
+
+	return true;
+}
+
+static bool
+adjust_limits_for_dsc_hblank_expansion_quirk(const struct intel_connector *connector,
+					     const struct intel_crtc_state *crtc_state,
+					     struct link_config_limits *limits,
+					     bool dsc)
+{
+	struct drm_i915_private *i915 = to_i915(connector->base.dev);
+	const struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
+	int min_bpp_x16 = limits->link.min_bpp_x16;
+
+	if (!hblank_expansion_quirk_needs_dsc(connector, crtc_state))
+		return true;
+
+	if (!dsc) {
+		drm_dbg_kms(&i915->drm,
+			    "[CRTC:%d:%s][CONNECTOR:%d:%s] DSC required by hblank expansion quirk\n",
+			    crtc->base.base.id, crtc->base.name,
+			    connector->base.base.id, connector->base.name);
+		return false;
+	}
+
+	drm_WARN_ON(&i915->drm, limits->min_rate != limits->max_rate);
+
+	if (limits->max_rate < 540000)
+		min_bpp_x16 = to_bpp_x16(13);
+	else if (limits->max_rate < 810000)
+		min_bpp_x16 = to_bpp_x16(10);
+
+	if (limits->link.min_bpp_x16 >= min_bpp_x16)
+		return true;
+
+	drm_dbg_kms(&i915->drm,
+		    "[CRTC:%d:%s][CONNECTOR:%d:%s] Increasing link min bpp to " BPP_X16_FMT " due to hblank expansion quirk\n",
+		    crtc->base.base.id, crtc->base.name,
+		    connector->base.base.id, connector->base.name,
+		    BPP_X16_ARGS(min_bpp_x16));
+
+	if (limits->link.max_bpp_x16 < min_bpp_x16)
+		return false;
+
+	limits->link.min_bpp_x16 = min_bpp_x16;
+
+	return true;
+}
+
 static bool
 intel_dp_mst_compute_config_limits(struct intel_dp *intel_dp,
+				   const struct intel_connector *connector,
 				   struct intel_crtc_state *crtc_state,
 				   bool dsc,
 				   struct link_config_limits *limits)
@@ -389,10 +458,16 @@  intel_dp_mst_compute_config_limits(struct intel_dp *intel_dp,
 
 	intel_dp_adjust_compliance_config(intel_dp, crtc_state, limits);
 
-	return intel_dp_compute_config_link_bpp_limits(intel_dp,
-						       crtc_state,
-						       dsc,
-						       limits);
+	if (!intel_dp_compute_config_link_bpp_limits(intel_dp,
+						     crtc_state,
+						     dsc,
+						     limits))
+		return false;
+
+	return adjust_limits_for_dsc_hblank_expansion_quirk(connector,
+							    crtc_state,
+							    limits,
+							    dsc);
 }
 
 static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
@@ -402,6 +477,8 @@  static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
 	struct intel_dp_mst_encoder *intel_mst = enc_to_mst(encoder);
 	struct intel_dp *intel_dp = &intel_mst->primary->dp;
+	const struct intel_connector *connector =
+		to_intel_connector(conn_state->connector);
 	const struct drm_display_mode *adjusted_mode =
 		&pipe_config->hw.adjusted_mode;
 	struct link_config_limits limits;
@@ -417,6 +494,7 @@  static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
 
 	dsc_needed = intel_dp->force_dsc_en ||
 		     !intel_dp_mst_compute_config_limits(intel_dp,
+							 connector,
 							 pipe_config,
 							 false,
 							 &limits);
@@ -439,6 +517,7 @@  static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
 			    str_yes_no(intel_dp->force_dsc_en));
 
 		if (!intel_dp_mst_compute_config_limits(intel_dp,
+							connector,
 							pipe_config,
 							true,
 							&limits))
@@ -1213,6 +1292,36 @@  intel_dp_mst_read_decompression_port_dsc_caps(struct intel_dp *intel_dp,
 	intel_dp_get_dsc_sink_cap(dpcd_caps[DP_DPCD_REV], connector);
 }
 
+static bool detect_dsc_hblank_expansion_quirk(const struct intel_connector *connector)
+{
+	struct drm_i915_private *i915 = to_i915(connector->base.dev);
+	struct drm_dp_desc desc;
+	u8 dpcd[DP_RECEIVER_CAP_SIZE];
+
+	if (!connector->dp.dsc_decompression_aux)
+		return false;
+
+	if (drm_dp_read_desc(connector->dp.dsc_decompression_aux,
+			     &desc, true) < 0)
+		return false;
+
+	if (!drm_dp_has_quirk(&desc,
+			      DP_DPCD_QUIRK_HBLANK_EXPANSION_REQUIRES_DSC))
+		return false;
+
+	if (drm_dp_read_dpcd_caps(connector->dp.dsc_decompression_aux, dpcd) < 0)
+		return false;
+
+	if (!(dpcd[DP_RECEIVE_PORT_0_CAP_0] & DP_HBLANK_EXPANSION_CAPABLE))
+		return false;
+
+	drm_dbg_kms(&i915->drm,
+		    "[CONNECTOR:%d:%s] DSC HBLANK expansion quirk detected\n",
+		    connector->base.base.id, connector->base.name);
+
+	return true;
+}
+
 static struct drm_connector *intel_dp_add_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
 							struct drm_dp_mst_port *port,
 							const char *pathprop)
@@ -1242,6 +1351,8 @@  static struct drm_connector *intel_dp_add_mst_connector(struct drm_dp_mst_topolo
 	 */
 	intel_connector->dp.dsc_decompression_aux = &intel_dp->aux;
 	intel_dp_mst_read_decompression_port_dsc_caps(intel_dp, intel_connector);
+	intel_connector->dp.dsc_hblank_expansion_quirk =
+		detect_dsc_hblank_expansion_quirk(intel_connector);
 
 	connector = &intel_connector->base;
 	ret = drm_connector_init(dev, connector, &intel_dp_mst_connector_funcs,