[PATCH 25/26] drm/i915: Try to probe DP++ dongles on DP++ downstream facing ports

[Ville Syrjala]

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

In order to get accurate TMDS clocks limits for the DP++ ports we
can try to probe the DP dual mode adapter registers. Unfortunately
I've not yet seen a DP->DP++ branch device that would actually
forward these i2c accesses to the dual mode dongle downstream.
But we don't lose much by trying and maybe it'll work on some
branch devices, if not now then maybe in the future.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 .../drm/i915/display/intel_display_types.h    |  1 +
 drivers/gpu/drm/i915/display/intel_dp.c       | 41 +++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 0d135859e9d4..5cd052f55662 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1316,6 +1316,7 @@ struct intel_dp {
 		u8 max_bpc;
 		bool ycbcr_444_to_420;
 	} dfp;
+	struct intel_dp_dual_mode dp_dual_mode;
 };
 
 enum lspcon_vendor {
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 3bf19d691fd5..5143c1b0fd92 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -608,6 +608,10 @@ intel_dp_mode_valid_downstream(struct intel_connector *connector,
 	    tmds_clock > intel_dp->dfp.max_tmds_clock)
 		return MODE_CLOCK_HIGH;
 
+	if (intel_dp->dp_dual_mode.max_tmds_clock &&
+	    tmds_clock > intel_dp->dp_dual_mode.max_tmds_clock)
+		return MODE_CLOCK_HIGH;
+
 	return MODE_OK;
 }
 
@@ -1762,6 +1766,8 @@ intel_dp_aux_init(struct intel_dp *intel_dp)
 				       aux_ch_name(dig_port->aux_ch),
 				       port_name(encoder->port));
 	intel_dp->aux.transfer = intel_dp_aux_transfer;
+
+	intel_dp->dp_dual_mode.adapter = &intel_dp->aux.ddc;
 }
 
 bool intel_dp_source_supports_hbr2(struct intel_dp *intel_dp)
@@ -1950,6 +1956,10 @@ static bool intel_dp_hdmi_tmds_clock_valid(struct intel_dp *intel_dp,
 	    tmds_clock > intel_dp->dfp.max_tmds_clock)
 		return false;
 
+	if (intel_dp->dp_dual_mode.max_tmds_clock &&
+	    tmds_clock > intel_dp->dp_dual_mode.max_tmds_clock)
+		return false;
+
 	return true;
 }
 
@@ -5850,6 +5860,35 @@ intel_dp_set_edid(struct intel_dp *intel_dp)
 	intel_dp_update_dfp(intel_dp, edid);
 	intel_dp_update_420(intel_dp);
 
+	if (drm_dp_downstream_is_tmds(intel_dp->dpcd,
+				      intel_dp->downstream_ports,
+				      edid)) {
+		/*
+		 * Most branch devices don't seem to forward the
+		 * DP dual mode i2c accesses to the dongle, so even
+		 * when you have a type2 HDMI dongle with a high TMDS
+		 * clock limit we may not be able to detect it :(
+		 * To avoid users complaining about losing high
+		 * resolution modes let's not assume type1 DVI
+		 * dongle presence when the access fails. There
+		 * doesn't seem to be any way to read the CONFIG1
+		 * pin state from the branch device.
+		 */
+		intel_dp_dual_mode_detect(connector, &intel_dp->dp_dual_mode, false);
+
+		/*
+		 * We drive LSPCON DP dual mode adaptors in PCON mode
+		 * so we should just ignore the HDMI side of it.
+		 */
+		if (intel_dp->dp_dual_mode.type == DRM_DP_DUAL_MODE_LSPCON) {
+			DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Ignoring LSPCON DP dual mode adaptor presence\n",
+				      connector->base.base.id,
+				      connector->base.name);
+
+			intel_dp_dual_mode_reset(&intel_dp->dp_dual_mode);
+		}
+	}
+
 	if (edid && edid->input & DRM_EDID_INPUT_DIGITAL) {
 		intel_dp->has_hdmi_sink = drm_detect_hdmi_monitor(edid);
 		intel_dp->has_audio = drm_detect_monitor_audio(edid);
@@ -5877,6 +5916,8 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
 
 	intel_dp->dfp.ycbcr_444_to_420 = false;
 	connector->base.ycbcr_420_allowed = false;
+
+	intel_dp_dual_mode_reset(&intel_dp->dp_dual_mode);
 }
 
 static int
-- 
2.24.1