drm/i915: Unbreak check_digital_port_conflicts()

Atomic changes broke check_digital_port_conflicts(). It needs to look
at the global situation instead of just trying to find a conflict
within the current atomic state.

This bug made my HSW explode spectacularly after I had split the DDI
encoders into separate DP and HDMI encoders. With the fix, things
seem much more solid.

I hope holding the connection_mutex is enough protection that we can
actually walk the connectors even if they're not part of the current
atomic state...

v2: Regenerate the patch so that it actually applies (Jani)

Cc: stable@vger.kernel.org
Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Fixes: 5448a00 ("drm/i915: Don't use staged config in check_digital_port_conflicts()")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1449764551-12466-1-git-send-email-ville.syrjala@linux.intel.com
(cherry picked from commit 0bff485)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -12123,18 +12123,22 @@ static void intel_dump_pipe_config(struct intel_crtc *crtc,
 static bool check_digital_port_conflicts(struct drm_atomic_state *state)
 {
 	struct drm_device *dev = state->dev;
-	struct intel_encoder *encoder;
 	struct drm_connector *connector;
-	struct drm_connector_state *connector_state;
 	unsigned int used_ports = 0;
-	int i;
 
 	/*
 	 * Walk the connector list instead of the encoder
 	 * list to detect the problem on ddi platforms
 	 * where there's just one encoder per digital port.
 	 */
-	for_each_connector_in_state(state, connector, connector_state, i) {
+	drm_for_each_connector(connector, dev) {
+		struct drm_connector_state *connector_state;
+		struct intel_encoder *encoder;
+
+		connector_state = drm_atomic_get_existing_connector_state(state, connector);
+		if (!connector_state)
+			connector_state = connector->state;
+
 		if (!connector_state->best_encoder)
 			continue;