Atm until the DPCD for a connector is read the max link rate and lane count params are invalid. If the connector is modeset, in intel_dp_compute_config(), intel_dp_common_len_rate_limit(max_link_rate) will return 0, leading to a intel_dp->common_rates[-1] access.
Fix the above by making sure the max link params are always valid.
The above access leads to an undefined behaviour by definition, though not causing a user visible problem to my best knowledge, see the previous patch why. Nevertheless it is an undefined behaviour and it triggers a BUG() in CONFIG_UBSAN builds, hence CC:stable.
Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: stable@vger.kernel.org Signed-off-by: Imre Deak imre.deak@intel.com --- drivers/gpu/drm/i915/display/intel_dp.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 153ae944a354b..1935eb49f9574 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -1864,6 +1864,12 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp, intel_dp->lane_count = lane_count; }
+static void intel_dp_reset_max_link_params(struct intel_dp *intel_dp) +{ + intel_dp->max_link_lane_count = intel_dp_max_common_lane_count(intel_dp); + intel_dp->max_link_rate = intel_dp_max_common_rate(intel_dp); +} + /* Enable backlight PWM and backlight PP control. */ void intel_edp_backlight_on(const struct intel_crtc_state *crtc_state, const struct drm_connector_state *conn_state) @@ -2023,8 +2029,7 @@ void intel_dp_sync_state(struct intel_encoder *encoder, if (intel_dp->dpcd[DP_DPCD_REV] == 0) intel_dp_get_dpcd(intel_dp);
- intel_dp->max_link_lane_count = intel_dp_max_common_lane_count(intel_dp); - intel_dp->max_link_rate = intel_dp_max_common_rate(intel_dp); + intel_dp_reset_max_link_params(intel_dp); }
bool intel_dp_initial_fastset_check(struct intel_encoder *encoder, @@ -2597,6 +2602,7 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp) intel_dp_set_sink_rates(intel_dp);
intel_dp_set_common_rates(intel_dp); + intel_dp_reset_max_link_params(intel_dp);
/* Read the eDP DSC DPCD registers */ if (DISPLAY_VER(dev_priv) >= 10) @@ -4338,12 +4344,7 @@ intel_dp_detect(struct drm_connector *connector, * supports link training fallback params. */ if (intel_dp->reset_link_params || intel_dp->is_mst) { - /* Initial max link lane count */ - intel_dp->max_link_lane_count = intel_dp_max_common_lane_count(intel_dp); - - /* Initial max link rate */ - intel_dp->max_link_rate = intel_dp_max_common_rate(intel_dp); - + intel_dp_reset_max_link_params(intel_dp); intel_dp->reset_link_params = false; }
@@ -5011,6 +5012,7 @@ intel_dp_init_connector(struct intel_digital_port *dig_port, intel_dp_set_source_rates(intel_dp); intel_dp_set_default_sink_rates(intel_dp); intel_dp_set_common_rates(intel_dp); + intel_dp_reset_max_link_params(intel_dp);
if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv)) intel_dp->pps.active_pipe = vlv_active_pipe(intel_dp);