It's possible to modeset a connector/mst port that has a 0 full_pbn
value: if the sink on the port deasserts its HPD and a branch device
reports this via a CSN with the port's ddps=0 and pdt!=NONE the driver
clears full_pbn, but the corresponding connector can be still
modesetted.
This happened on a DELL U2719D monitor as the branch device and an LG
27UL650-W daisy-chained to it, the LG monitor generating a long HPD
pulse (doing this for some reason always when waking up from some power
saving state).
Tune down the WARN about this scenario to a debug message.
v2: Use the correct atomic debug message level. (Lyude)
References: https://gitlab.freedesktop.org/drm/intel/-/issues/1917
Cc: Lyude Paul <lyude@redhat.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210216123448.410545-1-imre.deak@intel.com
if (!found)
return 0;
- /* This should never happen, as it means we tried to
- * set a mode before querying the full_pbn
+ /*
+ * This could happen if the sink deasserted its HPD line, but
+ * the branch device still reports it as attached (PDT != NONE).
*/
- if (WARN_ON(!port->full_pbn))
+ if (!port->full_pbn) {
+ drm_dbg_atomic(port->mgr->dev,
+ "[MSTB:%p] [MST PORT:%p] no BW available for the port\n",
+ port->parent, port);
return -EINVAL;
+ }
pbn_used = vcpi->pbn;
} else {