drm/radeon/kms: don't crash if no DDC bus on VGA/DVI connector.

This is strange - like really really strange, twilight zone of strange.
VGA ports have DDC buses, but sometimes for some reasons the BIOS
says we don't and we oops - AMD mentioned bios bugs so we'll have
to add quirks.

reported on irc by nirbheek and
https://bugzilla.redhat.com/show_bug.cgi?id=554323

Signed-off-by: Dave Airlie <airlied@redhat.com>

2 files changed, 22 insertions, 9 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
index 2d8e5a70f284..238188540017 100644
--- a/drivers/gpu/drm/radeon/radeon_connectors.c
+++ b/drivers/gpu/drm/radeon/radeon_connectors.c
@@ -580,16 +580,18 @@ static enum drm_connector_status radeon_vga_detect(struct drm_connector *connect
         struct radeon_connector *radeon_connector = to_radeon_connector(connector);
         struct drm_encoder *encoder;
         struct drm_encoder_helper_funcs *encoder_funcs;
-        bool dret;
+        bool dret = false;
         enum drm_connector_status ret = connector_status_disconnected;
 
         encoder = radeon_best_single_encoder(connector);
         if (!encoder)
                 ret = connector_status_disconnected;
 
-        radeon_i2c_do_lock(radeon_connector->ddc_bus, 1);
-        dret = radeon_ddc_probe(radeon_connector);
-        radeon_i2c_do_lock(radeon_connector->ddc_bus, 0);
+        if (radeon_connector->ddc_bus) {
+                radeon_i2c_do_lock(radeon_connector->ddc_bus, 1);
+                dret = radeon_ddc_probe(radeon_connector);
+                radeon_i2c_do_lock(radeon_connector->ddc_bus, 0);
+        }
         if (dret) {
                 if (radeon_connector->edid) {
                         kfree(radeon_connector->edid);
@@ -740,11 +742,13 @@ static enum drm_connector_status radeon_dvi_detect(struct drm_connector *connect
         struct drm_mode_object *obj;
         int i;
         enum drm_connector_status ret = connector_status_disconnected;
-        bool dret;
+        bool dret = false;
 
-        radeon_i2c_do_lock(radeon_connector->ddc_bus, 1);
-        dret = radeon_ddc_probe(radeon_connector);
-        radeon_i2c_do_lock(radeon_connector->ddc_bus, 0);
+        if (radeon_connector->ddc_bus) {
+                radeon_i2c_do_lock(radeon_connector->ddc_bus, 1);
+                dret = radeon_ddc_probe(radeon_connector);
+                radeon_i2c_do_lock(radeon_connector->ddc_bus, 0);
+        }
         if (dret) {
                 if (radeon_connector->edid) {
                         kfree(radeon_connector->edid);
diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 6a92f994cc26..7e17a362b54b 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -278,7 +278,7 @@ static void radeon_print_display_setup(struct drm_device *dev)
                 DRM_INFO("  %s\n", connector_names[connector->connector_type]);
                 if (radeon_connector->hpd.hpd != RADEON_HPD_NONE)
                         DRM_INFO("  %s\n", hpd_names[radeon_connector->hpd.hpd]);
-                if (radeon_connector->ddc_bus)
+                if (radeon_connector->ddc_bus) {
                         DRM_INFO("  DDC: 0x%x 0x%x 0x%x 0x%x 0x%x 0x%x 0x%x 0x%x\n",
                                  radeon_connector->ddc_bus->rec.mask_clk_reg,
                                  radeon_connector->ddc_bus->rec.mask_data_reg,
@@ -288,6 +288,15 @@ static void radeon_print_display_setup(struct drm_device *dev)
                                  radeon_connector->ddc_bus->rec.en_data_reg,
                                  radeon_connector->ddc_bus->rec.y_clk_reg,
                                  radeon_connector->ddc_bus->rec.y_data_reg);
+                } else {
+                        if (connector->connector_type == DRM_MODE_CONNECTOR_VGA ||
+                            connector->connector_type == DRM_MODE_CONNECTOR_DVII ||
+                            connector->connector_type == DRM_MODE_CONNECTOR_DVID ||
+                            connector->connector_type == DRM_MODE_CONNECTOR_DVIA ||
+                            connector->connector_type == DRM_MODE_CONNECTOR_HDMIA ||
+                            connector->connector_type == DRM_MODE_CONNECTOR_HDMIB)
+                                DRM_INFO("  DDC: no ddc bus - possible BIOS bug - please report to xorg-driver-ati@lists.x.org\n");
+                }
                 DRM_INFO("  Encoders:\n");
                 list_for_each_entry(encoder, &dev->mode_config.encoder_list, head) {
                         radeon_encoder = to_radeon_encoder(encoder);