drm/i915/dp: Disable the AUX DPCD probe quirk if it's not required

Reading DPCD registers has side-effects and some of these can cause a
problem for instance during link training. Based on this it's better to
avoid the probing quirk done before each DPCD register read, limiting
this to the monitor which requires it. The only known problematic
monitor is an external SST sink, so keep the quirk disabled always for
eDP and MST sinks. Reenable the quirk after a hotplug event and after
resuming from a power state without hotplug support, until the
subsequent EDID based detection.

v2: Add a helper for determining the need/setting the probing. (Jani)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://lore.kernel.org/r/20250609125556.109538-2-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 59e41b505191cfeca4e4d3367a8f08eb8f605a0a..277b40b13948ed964f20aa1243f76aa263615360 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -5790,6 +5790,28 @@ intel_dp_detect_sdp_caps(struct intel_dp *intel_dp)
                drm_dp_as_sdp_supported(&intel_dp->aux, intel_dp->dpcd);
 }
 
+static bool intel_dp_needs_dpcd_probe(struct intel_dp *intel_dp, bool force_on_external)
+{
+       struct intel_connector *connector = intel_dp->attached_connector;
+
+       if (intel_dp_is_edp(intel_dp))
+               return false;
+
+       if (force_on_external)
+               return true;
+
+       if (intel_dp->is_mst)
+               return false;
+
+       return drm_edid_has_quirk(&connector->base, DRM_EDID_QUIRK_DP_DPCD_PROBE);
+}
+
+void intel_dp_dpcd_set_probe(struct intel_dp *intel_dp, bool force_on_external)
+{
+       drm_dp_dpcd_set_probe(&intel_dp->aux,
+                             intel_dp_needs_dpcd_probe(intel_dp, force_on_external));
+}
+
 static int
 intel_dp_detect(struct drm_connector *_connector,
                struct drm_modeset_acquire_ctx *ctx,
@@ -5918,6 +5940,8 @@ out_unset_edid:
        if (status != connector_status_connected && !intel_dp->is_mst)
                intel_dp_unset_edid(intel_dp);
 
+       intel_dp_dpcd_set_probe(intel_dp, false);
+
        if (!intel_dp_is_edp(intel_dp))
                drm_dp_set_subconnector_property(&connector->base,
                                                 status,
@@ -5948,6 +5972,8 @@ intel_dp_force(struct drm_connector *_connector)
                return;
 
        intel_dp_set_edid(intel_dp);
+
+       intel_dp_dpcd_set_probe(intel_dp, false);
 }
 
 static int intel_dp_get_modes(struct drm_connector *_connector)
@@ -6320,10 +6346,11 @@ intel_dp_hpd_pulse(struct intel_digital_port *dig_port, bool long_hpd)
         * complete the DP tunnel BW request for the latter connector/encoder
         * waiting for this encoder's DPRX read, perform a dummy read here.
         */
-       if (long_hpd)
+       if (long_hpd) {
+               intel_dp_dpcd_set_probe(intel_dp, true);
+
                intel_dp_read_dprx_caps(intel_dp, dpcd);
 
-       if (long_hpd) {
                intel_dp->reset_link_params = true;
                intel_dp_invalidate_source_oui(intel_dp);
 

diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
index eff3414c05dbff0b83230460ec3c02fb6a6a7d9b..0657f568119662828344cfddbe876f2acf2596d9 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp.h
+++ b/drivers/gpu/drm/i915/display/intel_dp.h
@@ -213,5 +213,6 @@ int intel_dp_compute_min_hblank(struct intel_crtc_state *crtc_state,
                                const struct drm_connector_state *conn_state);
 
 int intel_dp_dsc_bpp_step_x16(const struct intel_connector *connector);
+void intel_dp_dpcd_set_probe(struct intel_dp *intel_dp, bool force_on_external);
 
 #endif /* __INTEL_DP_H__ */

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
index 411cf44747767c40ab1e5ca89d047dc1a20dd2da..829a7c0fbe4febaafe3ba8e026c7d161f3544c0f 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
@@ -834,6 +834,8 @@ void intel_dp_aux_init(struct intel_dp *intel_dp)
 
        intel_dp->aux.transfer = intel_dp_aux_transfer;
        cpu_latency_qos_add_request(&intel_dp->pm_qos, PM_QOS_DEFAULT_VALUE);
+
+       intel_dp_dpcd_set_probe(intel_dp, true);
 }
 
 static enum aux_ch default_aux_ch(struct intel_encoder *encoder)

diff --git a/drivers/gpu/drm/i915/display/intel_hotplug.c b/drivers/gpu/drm/i915/display/intel_hotplug.c
index 74fe398663d63096d767bfd3aef8105f46901146..901fda434af125161a376a9fcfb22950650d3013 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/display/intel_hotplug.c
@@ -33,6 +33,7 @@
 #include "intel_display_core.h"
 #include "intel_display_rpm.h"
 #include "intel_display_types.h"
+#include "intel_dp.h"
 #include "intel_hdcp.h"
 #include "intel_hotplug.h"
 #include "intel_hotplug_irq.h"
@@ -906,9 +907,14 @@ void intel_hpd_poll_enable(struct intel_display *display)
  */
 void intel_hpd_poll_disable(struct intel_display *display)
 {
+       struct intel_encoder *encoder;
+
        if (!HAS_DISPLAY(display))
                return;
 
+       for_each_intel_dp(display->drm, encoder)
+               intel_dp_dpcd_set_probe(enc_to_intel_dp(encoder), true);
+
        WRITE_ONCE(display->hotplug.poll_enabled, false);
 
        spin_lock_irq(&display->irq.lock);