qxl: limit monitor config read retries

When reading the monitor config fails, don't retry forever.  If it fails
ten times in a row just give up to avoid the driver hangs.  Also add a
small delay after each attempt, so the host has a chance to complete a
partial update.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1488363154-6889-3-git-send-email-kraxel@redhat.com

drivers/gpu/drm/qxl/qxl_display.c

@@ -157,19 +157,23 @@ static void qxl_update_offset_props(struct qxl_device *qdev)
 
 void qxl_display_read_client_monitors_config(struct qxl_device *qdev)
 {
-
 	struct drm_device *dev = &qdev->ddev;
-	int status;
+	int status, retries;
 
-	status = qxl_display_copy_rom_client_monitors_config(qdev);
-	while (status == MONITORS_CONFIG_BAD_CRC) {
-		qxl_io_log(qdev, "failed crc check for client_monitors_config,"
-				 " retrying\n");
+	for (retries = 0; retries < 10; retries++) {
 		status = qxl_display_copy_rom_client_monitors_config(qdev);
+		if (status != MONITORS_CONFIG_BAD_CRC)
+			break;
+		udelay(5);
+	}
+	if (status == MONITORS_CONFIG_BAD_CRC) {
+		qxl_io_log(qdev, "config: bad crc\n");
+		DRM_DEBUG_KMS("ignoring client monitors config: bad crc");
+		return;
 	}
 	if (status == MONITORS_CONFIG_UNCHANGED) {
-		qxl_io_log(qdev, "config unchanged\n");
-		DRM_DEBUG("ignoring unchanged client monitors config");
+		qxl_io_log(qdev, "config: unchanged\n");
+		DRM_DEBUG_KMS("ignoring client monitors config: unchanged");
 		return;
 	}