drm/radeon: Properly handle DDC probe for DP bridges

DDC information can be accessed using AUX CH

Fixes failure to probe monitors on some systems with
DP bridge chips.

agd5f: minor fixes

Signed-off-by: Niels Ole Salscheider <niels_ole@salscheider-online.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
diff --git a/drivers/gpu/drm/radeon/radeon_i2c.c b/drivers/gpu/drm/radeon/radeon_i2c.c
index c5bddd6..fc60b74 100644
--- a/drivers/gpu/drm/radeon/radeon_i2c.c
+++ b/drivers/gpu/drm/radeon/radeon_i2c.c
@@ -39,7 +39,7 @@
  * radeon_ddc_probe
  *
  */
-bool radeon_ddc_probe(struct radeon_connector *radeon_connector)
+bool radeon_ddc_probe(struct radeon_connector *radeon_connector, bool use_aux)
 {
 	u8 out = 0x0;
 	u8 buf[8];
@@ -63,7 +63,13 @@
 	if (radeon_connector->router.ddc_valid)
 		radeon_router_select_ddc_port(radeon_connector);
 
-	ret = i2c_transfer(&radeon_connector->ddc_bus->adapter, msgs, 2);
+	if (use_aux) {
+		struct radeon_connector_atom_dig *dig = radeon_connector->con_priv;
+		ret = i2c_transfer(&dig->dp_i2c_bus->adapter, msgs, 2);
+	} else {
+		ret = i2c_transfer(&radeon_connector->ddc_bus->adapter, msgs, 2);
+	}
+
 	if (ret != 2)
 		/* Couldn't find an accessible DDC on this connector */
 		return false;