On Wed, 2026-07-01 at 18:31 +0300, Imre Deak wrote: > The target maximum rate/lane count selected by the fallback logic may > exceed the current link_caps max_limits' rate/lane count, the latter of > which are used as a limit by the lookup functions when filtering allowed > configurations. To ensure the fallback search finds all relevant > candidates, temporarily reset the link_caps max_limits to the maximum > common supported capabilities. > > After the fallback search completes, set the link_caps max_limits to the > configuration selected by the fallback logic, as before, determining > the allowed configurations for a subsequent modeset. > > Signed-off-by: Imre Deak <[email protected]> > --- > .../drm/i915/display/intel_dp_link_training.c | 39 ++++++++++++++++--- > 1 file changed, 34 insertions(+), 5 deletions(-) > > 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 b521dd11b62a7..7fdcc299daea5 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c > +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c > @@ -1960,10 +1960,12 @@ static bool reduce_link_params(struct intel_dp > *intel_dp, const struct intel_crt > static int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp, > const struct > intel_crtc_state *crtc_state) > { > + struct intel_display *display = to_intel_display(intel_dp); > struct intel_dp_link_caps *link_caps = intel_dp->link.caps; > struct intel_dp_link_config max_link_limits; > int new_link_rate; > int new_lane_count; > + int err = -1; > > if (intel_dp_is_edp(intel_dp) && !intel_dp->use_max_params) { > lt_dbg(intel_dp, DP_PHY_DPRX, > @@ -1972,14 +1974,32 @@ static int > intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp, > return 0; > } > > + /* > + * Temporarily reset the max link limit before selecting the fallback > + * config. > + * > + * After fallback, the current logic narrows the allowed configurations > + * to the selected config's rate and lane count. That can make a later > + * fallback candidate fall outside the current max_limit, so reset it > + * before searching. > + * > + * TODO: Constrain the allowed configurations by only disabling > individual > + * configurations and remove setting maximum link parameters. > + */ > + intel_dp_link_caps_get_max_limits(link_caps, &max_link_limits); > + intel_dp_link_caps_reset_max_limits(link_caps); > + > if (!reduce_link_params(intel_dp, crtc_state, &new_link_rate, > &new_lane_count)) > - return -1; > + goto out_restore_max_limits; > > if (intel_dp_is_edp(intel_dp) && > !intel_dp_can_link_train_fallback_for_edp(intel_dp, new_link_rate, > new_lane_count)) { > lt_dbg(intel_dp, DP_PHY_DPRX, > "Retrying Link training for eDP with same parameters\n"); > - return 0; > + > + err = 0; > + > + goto out_restore_max_limits; > } > > lt_dbg(intel_dp, DP_PHY_DPRX, > @@ -1990,10 +2010,19 @@ static int > intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp, > max_link_limits.rate = new_link_rate; > max_link_limits.lane_count = new_lane_count; > > - /* TODO: handle an update failure */ > - intel_dp_link_caps_set_max_limits(link_caps, &max_link_limits); > + err = 0; > > - return 0; > +out_restore_max_limits: > + /* > + * Shouldn't fail: setting max_limits can only fail if they drop below > + * the optionally forced rate/lane-count parameters, but the reduced > + * config was chosen to satisfy those constraints. > + */ > + if (drm_WARN_ON(display->drm, > + !intel_dp_link_caps_set_max_limits(link_caps, > &max_link_limits))) > + err = -1; > + > + return err; > } > > static bool intel_dp_schedule_fallback_link_training(struct > intel_atomic_state *state,
Reviewed-by: Luca Coelho <[email protected]> -- Cheers, Luca.
