drm/i915/crt: Do not rely upon the HPD presence pin

Whilst most monitors do wire up the HPD presence pin, it seems quite a
few KVM do not. Therefore if we simply rely on the HPD pin being
asserted to indicate a connected monitor we fail miserable, so fall back
to performing a DCC query for the EDID.

Reported-and-tested-by: Matthieu LAVIE <boiteamadmax@hotmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50501
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index 75a70c46ef1b..844e93e1e395 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -453,13 +453,15 @@ intel_crt_detect(struct drm_connector *connector, bool force)
         struct intel_load_detect_pipe tmp;
 
         if (I915_HAS_HOTPLUG(dev)) {
+                /* We can not rely on the HPD pin always being correctly wired
+                 * up, for example many KVM do not pass it through, and so
+                 * only trust an assertion that the monitor is connected.
+                 */
                 if (intel_crt_detect_hotplug(connector)) {
                         DRM_DEBUG_KMS("CRT detected via hotplug\n");
                         return connector_status_connected;
-                } else {
+                } else
                         DRM_DEBUG_KMS("CRT not detected via hotplug\n");
-                        return connector_status_disconnected;
-                }
         }
 
         if (intel_crt_detect_ddc(connector))