drm/i915/fbdev: Actually configure untiled displays

If we skipped all the connectors that were not part of a tile, we would
leave conn_seq=0 and conn_configured=0, convincing ourselves that we
had stagnated in our configuration attempts. Avoid this situation by
starting conn_seq=ALL_CONNECTORS, and repeating until we find no more
connectors to configure.

Fixes: 754a7659 ("drm/i915/fbdev: Stop repeating tile configuration on stagnation")
Reported-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190215123019.32283-1-chris@chris-wilson.co.uk
Cc: <stable@vger.kernel.org> # v3.19+
(cherry picked from commit d9b308b1)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_fbdev.c

@@ -336,8 +336,8 @@ static bool intel_fb_initial_config(struct drm_fb_helper *fb_helper,
 				    bool *enabled, int width, int height)
 {
 	struct drm_i915_private *dev_priv = to_i915(fb_helper->dev);
-	unsigned long conn_configured, conn_seq, mask;
 	unsigned int count = min(fb_helper->connector_count, BITS_PER_LONG);
+	unsigned long conn_configured, conn_seq;
 	int i, j;
 	bool *save_enabled;
 	bool fallback = true, ret = true;
@@ -355,10 +355,9 @@ static bool intel_fb_initial_config(struct drm_fb_helper *fb_helper,
 		drm_modeset_backoff(&ctx);
 
 	memcpy(save_enabled, enabled, count);
-	mask = GENMASK(count - 1, 0);
+	conn_seq = GENMASK(count - 1, 0);
 	conn_configured = 0;
 retry:
-	conn_seq = conn_configured;
 	for (i = 0; i < count; i++) {
 		struct drm_fb_helper_connector *fb_conn;
 		struct drm_connector *connector;
@@ -371,7 +370,8 @@ static bool intel_fb_initial_config(struct drm_fb_helper *fb_helper,
 		if (conn_configured & BIT(i))
 			continue;
 
-		if (conn_seq == 0 && !connector->has_tile)
+		/* First pass, only consider tiled connectors */
+		if (conn_seq == GENMASK(count - 1, 0) && !connector->has_tile)
 			continue;
 
 		if (connector->status == connector_status_connected)
@@ -475,8 +475,10 @@ static bool intel_fb_initial_config(struct drm_fb_helper *fb_helper,
 		conn_configured |= BIT(i);
 	}
 
-	if ((conn_configured & mask) != mask && conn_configured != conn_seq)
+	if (conn_configured != conn_seq) { /* repeat until no more are found */
+		conn_seq = conn_configured;
 		goto retry;
+	}
 
 	/*
 	 * If the BIOS didn't enable everything it could, fall back to have the