[PATCH v3] drm: Fire off KMS hotplug events if probe detect says the connector is connected

[Gwan-gyeong Mun]

The hotplug detection routine of drm_helper_hpd_irq_event() can detect
changing of status of connector, but it can not detect changing of
properties of the connector.
e.g. changing of edid while suspend/resume, changing of dp lanes in dp aux.

Following scenario explains one of them; A detection of changing of edid.

 1) plug display device to a connector
 2) system suspend
 3) unplug 1)'s display device and plug the other display device to a
    connector
 4) system resume

To solve explained cases, It fires off KMS hotplug events if
drm_helper_probe_detect() says the connector is connected.

Testcase: igt/kms_chamelium/hdmi-edid-change-during-hibernate
Testcase: igt/kms_chamelium/hdmi-edid-change-during-suspend
Testcase: igt/kms_chamelium/dp-edid-change-during-hibernate
Testcase: igt/kms_chamelium/dp-edid-change-during-suspend

v2: Remove suggested-by line (danvet)
v3: Remove a misused Link line and add References (Jani)

References: https://bugs.freedesktop.org/show_bug.cgi?id=105540
References: https://lists.freedesktop.org/archives/dri-devel/2019-April/214572.html
Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
---
 drivers/gpu/drm/drm_probe_helper.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 6fd08e04b323..081a849104f2 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -780,7 +780,8 @@ bool drm_helper_hpd_irq_event(struct drm_device *dev)
 			      connector->name,
 			      drm_get_connector_status_name(old_status),
 			      drm_get_connector_status_name(connector->status));
-		if (old_status != connector->status)
+		if (old_status != connector->status ||
+		    connector->status == connector_status_connected)
 			changed = true;
 	}
 	drm_connector_list_iter_end(&conn_iter);
-- 
2.21.0