FAILED: patch "[PATCH] drm/amdgpu/dce: Don't turn off DP sink when disconnected" failed to apply to 4.16-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.16-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From daf8809626c0ee7a152f9c34058fc3b43385dd51 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michel=20D=C3=A4nzer?= <michel.daenzer@amd.com>
Date: Fri, 9 Mar 2018 18:26:18 +0100
Subject: [PATCH] drm/amdgpu/dce: Don't turn off DP sink when disconnected
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Turning off the sink in this case causes various issues, because
userspace expects it to stay on until it turns it off explicitly.

Instead, turn the sink off and back on when a display is connected
again. This dance seems necessary for link training to work correctly.

Bugzilla: https://bugs.freedesktop.org/105308
Cc: stable@vger.kernel.org
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
index ffc1f6f46913..9da8d5802980 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
@@ -69,25 +69,18 @@ void amdgpu_connector_hotplug(struct drm_connector *connector)
 		/* don't do anything if sink is not display port, i.e.,
 		 * passive dp->(dvi|hdmi) adaptor
 		 */
-		if (dig_connector->dp_sink_type == CONNECTOR_OBJECT_ID_DISPLAYPORT) {
-			int saved_dpms = connector->dpms;
-			/* Only turn off the display if it's physically disconnected */
-			if (!amdgpu_display_hpd_sense(adev, amdgpu_connector->hpd.hpd)) {
-				drm_helper_connector_dpms(connector, DRM_MODE_DPMS_OFF);
-			} else if (amdgpu_atombios_dp_needs_link_train(amdgpu_connector)) {
-				/* Don't try to start link training before we
-				 * have the dpcd */
-				if (amdgpu_atombios_dp_get_dpcd(amdgpu_connector))
-					return;
-
-				/* set it to OFF so that drm_helper_connector_dpms()
-				 * won't return immediately since the current state
-				 * is ON at this point.
-				 */
-				connector->dpms = DRM_MODE_DPMS_OFF;
-				drm_helper_connector_dpms(connector, DRM_MODE_DPMS_ON);
-			}
-			connector->dpms = saved_dpms;
+		if (dig_connector->dp_sink_type == CONNECTOR_OBJECT_ID_DISPLAYPORT &&
+		    amdgpu_display_hpd_sense(adev, amdgpu_connector->hpd.hpd) &&
+		    amdgpu_atombios_dp_needs_link_train(amdgpu_connector)) {
+			/* Don't start link training before we have the DPCD */
+			if (amdgpu_atombios_dp_get_dpcd(amdgpu_connector))
+				return;
+
+			/* Turn the connector off and back on immediately, which
+			 * will trigger link training
+			 */
+			drm_helper_connector_dpms(connector, DRM_MODE_DPMS_OFF);
+			drm_helper_connector_dpms(connector, DRM_MODE_DPMS_ON);
 		}
 	}
 }