drm/radeon/kms: fix dp_detect handling for DP bridge chips

BugLink: http://bugs.launchpad.net/bugs/825777

The HPD pin is not reliable for detecting whether a monitor
is connected or not.  Skip HPD and just use DDC or load
detection.

Fixes phantom VGA connected bugs.

[Michel: fixes phantom VGA bugs on his llano system.]

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Tested-by: Michel Dänzer <michel.daenzer@amd.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
(cherry picked from commit 6777a4f6898a53974ef7fe7ce09ec41fae0f32db)
Signed-off-by: Wen-chien Jesse Sung <jesse.sung@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Andy Whitcroft <andy.whitcroft@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

1 files changed, 6 insertions, 15 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
index 9eec29276ff..800eadfdd0c 100644
--- a/drivers/gpu/drm/radeon/radeon_connectors.c
+++ b/drivers/gpu/drm/radeon/radeon_connectors.c
@@ -1315,23 +1315,14 @@ radeon_dp_detect(struct drm_connector *connector, bool force)
                 /* get the DPCD from the bridge */
                 radeon_dp_getdpcd(radeon_connector);
 
-                if (radeon_hpd_sense(rdev, radeon_connector->hpd.hpd))
-                        ret = connector_status_connected;
-                else {
-                        /* need to setup ddc on the bridge */
-                        if (encoder)
-                                radeon_atom_ext_encoder_setup_ddc(encoder);
+                if (encoder) {
+                        /* setup ddc on the bridge */
+                        radeon_atom_ext_encoder_setup_ddc(encoder);
                         if (radeon_ddc_probe(radeon_connector,
-                                             radeon_connector->requires_extended_probe))
+                                             radeon_connector->requires_extended_probe)) /* try DDC */
                                 ret = connector_status_connected;
-                }
-
-                if ((ret == connector_status_disconnected) &&
-                    radeon_connector->dac_load_detect) {
-                        struct drm_encoder *encoder = radeon_best_single_encoder(connector);
-                        struct drm_encoder_helper_funcs *encoder_funcs;
-                        if (encoder) {
-                                encoder_funcs = encoder->helper_private;
+                        else if (radeon_connector->dac_load_detect) { /* try load detection */
+                                struct drm_encoder_helper_funcs *encoder_funcs = encoder->helper_private;
                                 ret = encoder_funcs->detect(encoder, connector);
                         }
                 }