Below is the dmesg representing a video mode set.
ELD writes from the graphics driver
[ 424.254958] [drm:intel_write_eld], ELD on [CONNECTOR:12:HDMI-A-2], [ENCODER:11:TMDS-11] [ 424.257670] [drm:ironlake_write_eld], ELD on pipe B [ 424.259833] [drm:ironlake_write_eld], Audio directed to unknown port [ 424.262156] [drm:ironlake_write_eld], ELD size 13
ELD events received by audio driver (eld reads 0)
[ 424.263258] HDMI hot plug event: Codec=3 Pin=6 Presence_Detect=1 ELD_Valid=0
That line makes sense.
[ 424.265877] HDMI status: Codec=3 Pin=6 Presence_Detect=1 ELD_Valid=1
I don't /think/ it's related to this issue, but I wonder why ELDV==1 in that message; it seems that the unsolicited response contains the correct data, but AC_VERB_GET_PIN_SENSE contains ELDV==1 all the time. That's odd.
It depends on timing. When audio driver receives the unsolicited event, graphics driver has finished with "eld_valid = 1", hence AC_VERB_GET_PIN_SENSE returns ELDV=1.
It's not happening /all the time/ though. For example here is another dmesg showing a different timing on the same test box.
Sorry this is actually from another test box. But I did see similar ones from the same test box.
[ 467.561516] [drm:intel_dp_mode_set], Enabling DP audio on pipe B [ 467.567503] [drm:intel_write_eld], ELD on [CONNECTOR:26:DP-3], [ENCODER:27:TMDS-27] [ 467.574207] [drm:ironlake_write_eld], ELD on pipe B [ 467.579346] [drm:ironlake_write_eld], Audio directed to unknown port [ 467.584724] [drm:ironlake_write_eld], ELD: DisplayPort detected [ 467.586540] HDMI hot plug event: Codec=3 Pin=7 Presence_Detect=1 ELD_Valid=0 [ 467.599608] [drm:ironlake_write_eld], [ 467.599922] HDMI status: Codec=3 Pin=7 Presence_Detect=1 ELD_Valid=0 [ 467.605834] ELD size 9 [ 467.610434] [drm:sandybridge_update_wm], FIFO watermarks For pipe A - plane 7, cursor: 6 [ 467.612365] HDMI hot plug event: Codec=3 Pin=7 Presence_Detect=1 ELD_Valid=1 [ 467.620654] [drm:sandybridge_update_wm], [ 467.620765] HDMI status: Codec=3 Pin=7 Presence_Detect=1 ELD_Valid=1