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

1 files changed, 33 insertions, 25 deletions

diff --git a/drivers/gpu/drm/omapdrm/omap_encoder.c b/drivers/gpu/drm/omapdrm/omap_encoder.c
index 452e625f6ce3..933ebc9f9faa 100644
--- 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)