[PATCH RFC 10/12] drm/i915/display/dp: Adopt dp_connector helpers to expose link training state

Kory Maincent
2026-04-09T17:09:34Z

Switch the i915 DP connector initialization from drmm_connector_init()
to drmm_connector_dp_init(), providing the source link capabilities
(supported lane counts, link rates, DSC support, voltage swing and
pre-emphasis levels).

Add intel_dp_report_link_train() to collect the negotiated link
parameters (rate, lane count, DSC enable, per-lane voltage swing and
pre-emphasis) and report them via drm_connector_dp_set_link_train_properties()
once link training completes successfully.

Reset the link training properties via
drm_connector_dp_reset_link_train_properties() when the connector is
reported as disconnected or when the display device is disabled, so
the exposed state always reflects the current link status.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
---
drivers/gpu/drm/i915/display/intel_dp.c | 31 +++++++++++++++++++---
.../gpu/drm/i915/display/intel_dp_link_training.c | 25 +++++++++++++++++
2 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 2af64de9c81de..641406bdc0cc9 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -45,6 +45,7 @@
#include <drm/display/drm_hdmi_helper.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_crtc.h>
+#include <drm/drm_dp_connector.h>
#include <drm/drm_edid.h>
#include <drm/drm_fixed.h>
#include <drm/drm_managed.h>
@@ -6337,8 +6338,10 @@ intel_dp_detect(struct drm_connector *_connector,
drm_WARN_ON(display->drm,
!drm_modeset_is_locked(&display->drm->mode_config.connection_mutex));

- if (!intel_display_device_enabled(display))
+ if (!intel_display_device_enabled(display)) {
+ drm_connector_dp_reset_link_train_properties(_connector);
return connector_status_disconnected;
+ }

if (!intel_display_driver_check_access(display))
return connector->base.status;
@@ -6388,6 +6391,8 @@ intel_dp_detect(struct drm_connector *_connector,

intel_dp_tunnel_disconnect(intel_dp);

+ drm_connector_dp_reset_link_train_properties(_connector);
+
goto out_unset_edid;
}

@@ -7162,10 +7167,12 @@ intel_dp_init_connector(struct intel_digital_port *dig_port,
struct intel_connector *connector)
{
struct intel_display *display = to_intel_display(dig_port);
+ struct drm_connector_dp_link_train_caps link_caps;
struct intel_dp *intel_dp = &dig_port->dp;
struct intel_encoder *encoder = &dig_port->base;
struct drm_device *dev = encoder->base.dev;
enum port port = encoder->port;
+ u32 *rates;
int type;

if (drm_WARN(dev, dig_port->max_lanes < 1,
@@ -7213,8 +7220,25 @@ intel_dp_init_connector(struct intel_digital_port *dig_port,
type == DRM_MODE_CONNECTOR_eDP ? "eDP" : "DP",
encoder->base.base.id, encoder->base.name);

- drmm_connector_init(dev, &connector->base, &intel_dp_connector_funcs,
- type, &intel_dp->aux.ddc);
+ intel_dp_set_source_rates(intel_dp);
+ link_caps.nlanes = DRM_DP_1LANE | DRM_DP_2LANE | DRM_DP_4LANE;
+ link_caps.nrates = intel_dp->num_source_rates;
+ rates = kzalloc_objs(*rates, intel_dp->num_source_rates);
+ if (!rates)
+ goto fail;
+
+ for (int i = 0; i < intel_dp->num_source_rates; i++)
+ rates[i] = intel_dp->source_rates[i];
+
+ link_caps.rates = rates;
+ link_caps.dsc = true;
+ link_caps.v_swings = DRM_DP_VOLTAGE_SWING_LEVEL_MASK;
+ link_caps.pre_emphs = DRM_DP_PRE_EMPH_LEVEL_MASK;
+
+ drmm_connector_dp_init(dev, &connector->base, &intel_dp_connector_funcs,
+ &link_caps, type, &intel_dp->aux.ddc);
+ kfree(rates);
+
drm_connector_helper_add(&connector->base, &intel_dp_connector_helper_funcs);

if (drmm_add_action_or_reset(dev, intel_connector_destroy, connector)) {
@@ -7240,7 +7264,6 @@ intel_dp_init_connector(struct intel_digital_port *dig_port,
if (!intel_edp_init_connector(intel_dp, connector))
goto fail;

- intel_dp_set_source_rates(intel_dp);
intel_dp_set_common_rates(intel_dp);
intel_dp_reset_link_params(intel_dp);

diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index 54c585c59b900..c2fd46a323650 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -25,6 +25,7 @@
#include <linux/iopoll.h>

#include <drm/display/drm_dp_helper.h>
+#include <drm/drm_dp_connector.h>
#include <drm/drm_print.h>

#include "intel_display_core.h"
@@ -1116,6 +1117,27 @@ intel_dp_128b132b_intra_hop(struct intel_dp *intel_dp,
return sink_status & DP_INTRA_HOP_AUX_REPLY_INDICATION ? 1 : 0;
}

+static void intel_dp_report_link_train(struct intel_dp *intel_dp)
+{
+ struct intel_connector *connector = intel_dp->attached_connector;
+ struct drm_connector_dp_link_train dp_link_train;
+
+ dp_link_train.rate = intel_dp->link_rate;
+ dp_link_train.nlanes = intel_dp->lane_count;
+ dp_link_train.dsc_en = connector->dp.dsc_decompression_enabled;
+
+ for (int i = 0; i < intel_dp->lane_count; i++) {
+ int v_swing_level = (intel_dp->train_set[i] &
+ DP_TRAIN_VOLTAGE_SWING_MASK) >> DP_TRAIN_VOLTAGE_SWING_SHIFT;
+ int pre_emph_level = (intel_dp->train_set[i] &
+ DP_TRAIN_PRE_EMPHASIS_MASK) >> DP_TRAIN_PRE_EMPHASIS_SHIFT;
+ dp_link_train.v_swing[i] = 1 << v_swing_level;
+ dp_link_train.pre_emph[i] = 1 << pre_emph_level;
+ }
+
+ drm_connector_dp_set_link_train_properties(&connector->base, &dp_link_train);
+}
+
/**
* intel_dp_stop_link_train - stop link training
* @intel_dp: DP struct
@@ -1144,6 +1166,9 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp,
intel_dp_program_link_training_pattern(intel_dp, crtc_state, DP_PHY_DPRX,
DP_TRAINING_PATTERN_DISABLE);

+ if (!intel_dp->is_mst)
+ intel_dp_report_link_train(intel_dp);
+
if (intel_dp_is_uhbr(crtc_state)) {
ret = poll_timeout_us(ret = intel_dp_128b132b_intra_hop(intel_dp, crtc_state),
ret == 0,

--
2.43.0