drm/omap: fix incorrect union usage

The DSI encoder sets dssdev->ops->dsi.set_config, which is stored at the
same offset as dssdev->ops->hdmi.set_hdmi_mode. The code in omap_encoder
only checks if dssdev->ops->hdmi.set_hdmi_mode is NULL. Due to the way
union works, it won't be NULL if dsi.set_config is set. This means
dsi_set_config will be called with config=hdmi_mode=false=NULL parameter
resulting in a NULL dereference. Also the dereference happens while
console is locked, so kernel hangs without any debug output without
"fb.lockless_register_fb=1" parameter.

This restructures the code, so that the HDMI mode is only configured
for HDMI output types.

Fixes: 83910ad3f51fb ("drm/omap: Move most omap_dss_driver operations to omap_dss_device_ops")
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Tested-by: Tony Lindgren <tony@atomide.com>
[tomi.valkeinen@ti.com: dropped the safeguard]
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181121160916.22017-5-sebastian.reichel@collabora.com

diff --git a/drivers/gpu/drm/omapdrm/omap_encoder.c b/drivers/gpu/drm/omapdrm/omap_encoder.c
index 452e625..933ebc9 100644 (file)
--- a/drivers/gpu/drm/omapdrm/omap_encoder.c
+++ b/drivers/gpu/drm/omapdrm/omap_encoder.c
@@ -52,17 +52,44 @@ static const struct drm_encoder_funcs omap_encoder_funcs = {
        .destroy = omap_encoder_destroy,
 };
 
+static void omap_encoder_hdmi_mode_set(struct drm_encoder *encoder,
+                                      struct drm_display_mode *adjusted_mode)
+{
+       struct drm_device *dev = encoder->dev;
+       struct omap_encoder *omap_encoder = to_omap_encoder(encoder);
+       struct omap_dss_device *dssdev = omap_encoder->output;
+       struct drm_connector *connector;
+       bool hdmi_mode;
+
+       hdmi_mode = false;
+       list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
+               if (connector->encoder == encoder) {
+                       hdmi_mode = omap_connector_get_hdmi_mode(connector);
+                       break;
+               }
+       }
+
+       if (dssdev->ops->hdmi.set_hdmi_mode)
+               dssdev->ops->hdmi.set_hdmi_mode(dssdev, hdmi_mode);
+
+       if (hdmi_mode && dssdev->ops->hdmi.set_infoframe) {
+               struct hdmi_avi_infoframe avi;
+               int r;
+
+               r = drm_hdmi_avi_infoframe_from_display_mode(&avi, adjusted_mode,
+                                                            false);
+               if (r == 0)
+                       dssdev->ops->hdmi.set_infoframe(dssdev, &avi);
+       }
+}
+
 static void omap_encoder_mode_set(struct drm_encoder *encoder,
                                  struct drm_display_mode *mode,
                                  struct drm_display_mode *adjusted_mode)
 {
-       struct drm_device *dev = encoder->dev;
        struct omap_encoder *omap_encoder = to_omap_encoder(encoder);
-       struct drm_connector *connector;
        struct omap_dss_device *dssdev;
        struct videomode vm = { 0 };
-       bool hdmi_mode;
-       int r;
 
        drm_display_mode_to_videomode(adjusted_mode, &vm);
 
@@ -112,27 +139,8 @@ static void omap_encoder_mode_set(struct drm_encoder *encoder,
        }
 
        /* Set the HDMI mode and HDMI infoframe if applicable. */
-       hdmi_mode = false;
-       list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
-               if (connector->encoder == encoder) {
-                       hdmi_mode = omap_connector_get_hdmi_mode(connector);
-                       break;
-               }
-       }
-
-       dssdev = omap_encoder->output;
-
-       if (dssdev->ops->hdmi.set_hdmi_mode)
-               dssdev->ops->hdmi.set_hdmi_mode(dssdev, hdmi_mode);
-
-       if (hdmi_mode && dssdev->ops->hdmi.set_infoframe) {
-               struct hdmi_avi_infoframe avi;
-
-               r = drm_hdmi_avi_infoframe_from_display_mode(&avi, adjusted_mode,
-                                                            false);
-               if (r == 0)
-                       dssdev->ops->hdmi.set_infoframe(dssdev, &avi);
-       }
+       if (omap_encoder->output->output_type == OMAP_DISPLAY_TYPE_HDMI)
+               omap_encoder_hdmi_mode_set(encoder, adjusted_mode);
 }
 
 static void omap_encoder_disable(struct drm_encoder *encoder)