Apparently been in there since forever and fairly easy to hit when hotplugging really fast. I can do that since my mst hub has a manual button to flick the hpd line for reprobing. The resulting WARNING spam isn't pretty.

Cc Dave Airlie <[email protected]>

Reviewed-by Thierry Reding <[email protected]>

Reviewed-by Ander Conselvan de Oliveira <[email protected]>

Signed-off-by Daniel Vetter <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 drivers/gpu/drm/drm_dp_mst_topology.c |    1 -
 1 file changed, 1 deletion(-)

drivers/gpu/drm/drm_dp_mst_topology.c +0 -1

@@ -1294,7 +1294,6 @@ retry:
 				goto retry;
 			}
 			DRM_DEBUG_KMS("failed to dpcd write %d %d\n", tosend, ret);
-			WARN(1, "fail\n");
 
 			return -EIO;
 		}

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/drm-i915-declare-the-swizzling-unknown-for-l-shaped-configurations.patch queue-4.1/drm-i915-replace-warn-inside-i915_read64_2x32-with-retry-loop.patch queue-4.1/drm-dp-mst-remove-debug-warn_on.patch