Instead of silently giving up when all link-training fallback values are exhausted, this patch modifies the fallback's failure branch to reduces both max_link_lane_count and max_link_rate to zero (0) and continues to emit uevents until userspace stops attempting to modeset. By doing so, we ensure the failing connector, which is in link-status=Bad, has all its modes pruned (due to effectively having a bandwidth of 0Gbps). It is then the userspace's responsibility to ignore connectors with no modes, even if they are marked as connected. Signed-off-by: Gil Dekel <gildekel@xxxxxxxxxxxx> --- drivers/gpu/drm/i915/display/intel_dp.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 7067ee3a4bd3..2152ddbab557 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -276,8 +276,12 @@ static int intel_dp_common_len_rate_limit(const struct intel_dp *intel_dp, static int intel_dp_common_rate(struct intel_dp *intel_dp, int index) { + /* This occurs when max link rate drops to 0 via link training fallback*/ + if (index < 0) + return 0; + if (drm_WARN_ON(&dp_to_i915(intel_dp)->drm, - index < 0 || index >= intel_dp->num_common_rates)) + index >= intel_dp->num_common_rates)) return 162000; return intel_dp->common_rates[index]; @@ -318,6 +322,9 @@ static int intel_dp_max_common_lane_count(struct intel_dp *intel_dp) int intel_dp_max_lane_count(struct intel_dp *intel_dp) { switch (intel_dp->max_link_lane_count) { + /* This occurs when max link lane count drops to 0 via link training fallback*/ + case 0: + return 0; case 1: case 2: case 4: @@ -672,7 +679,14 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp, intel_dp->max_link_lane_count = lane_count >> 1; } else { drm_err(&i915->drm, "Link Training Unsuccessful\n"); - return -1; + /* + * Ensure all of the connector's modes are pruned in the next + * probe by effectively reducing its bandwidth to 0 so userspace + * can ignore it within the next modeset attempt. + */ + intel_dp->max_link_rate = 0; + intel_dp->max_link_lane_count = 0; + return 0; } return 0; -- Gil Dekel, Software Engineer, Google / ChromeOS Display and Graphics