drm/nouveau/dp: Don't probe eDP ports twice harder

I didn't pay close enough attention the last time I tried to fix this
problem - while we currently do correctly take care to make sure we don't
probe a connected eDP port more then once, we don't do the same thing for
eDP ports we found to be disconnected.

So, fix this and make sure we only ever probe eDP ports once and then leave
them at that connector state forever (since without HPD, it's not going to
change on its own anyway). This should get rid of the last few GSP errors
getting spit out during runtime suspend and resume on some machines, as we
tried to reprobe eDP ports in response to ACPI hotplug probe events.
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240404233736.7946-3-lyude@redhat.com
(cherry picked from commit fe6660b6)

drivers/gpu/drm/nouveau/nouveau_dp.c

@@ -225,12 +225,15 @@ nouveau_dp_detect(struct nouveau_connector *nv_connector,
 	u8 *dpcd = nv_encoder->dp.dpcd;
 	int ret = NOUVEAU_DP_NONE, hpd;
 
-	/* If we've already read the DPCD on an eDP device, we don't need to
-	 * reread it as it won't change
+	/* eDP ports don't support hotplugging - so there's no point in probing eDP ports unless we
+	 * haven't probed them once before.
 	 */
-	if (connector->connector_type == DRM_MODE_CONNECTOR_eDP &&
-	    dpcd[DP_DPCD_REV] != 0)
-		return NOUVEAU_DP_SST;
+	if (connector->connector_type == DRM_MODE_CONNECTOR_eDP) {
+		if (connector->status == connector_status_connected)
+			return NOUVEAU_DP_SST;
+		else if (connector->status == connector_status_disconnected)
+			return NOUVEAU_DP_NONE;
+	}
 
 	// Ensure that the aux bus is enabled for probing
 	drm_dp_dpcd_set_powered(&nv_connector->aux, true);