[PATCH] drm/radeon: on hotplug force link training to happen

[j.glisse at gmail.com]

From: Jerome Glisse <jglisse at redhat.com>

To have kernel behave like VGA/DVI we need to retrain link
on hotplug. For this to happen with need to report that
we need to link training to happen if we fail to get link
status and we need to force link training to happen by
setting connector dpms to off before asking it on.

Signed-off-by: Jerome Glisse <jglisse at redhat.com>
---
 drivers/gpu/drm/radeon/atombios_dp.c       |    2 +-
 drivers/gpu/drm/radeon/radeon_connectors.c |    7 +++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/radeon/atombios_dp.c b/drivers/gpu/drm/radeon/atombios_dp.c
index 5131b3b..7bb5d7e 100644
--- a/drivers/gpu/drm/radeon/atombios_dp.c
+++ b/drivers/gpu/drm/radeon/atombios_dp.c
@@ -670,7 +670,7 @@ bool radeon_dp_needs_link_train(struct radeon_connector *radeon_connector)
 	struct radeon_connector_atom_dig *dig = radeon_connector->con_priv;
 
 	if (!radeon_dp_get_link_status(radeon_connector, link_status))
-		return false;
+		return true;
 	if (dp_channel_eq_ok(link_status, dig->dp_lane_count))
 		return false;
 	return true;
diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
index 2914c57..4b42c9f 100644
--- a/drivers/gpu/drm/radeon/radeon_connectors.c
+++ b/drivers/gpu/drm/radeon/radeon_connectors.c
@@ -67,10 +67,13 @@ void radeon_connector_hotplug(struct drm_connector *connector)
 		int saved_dpms = connector->dpms;
 
 		/* Only turn off the display it it's physically disconnected */
-		if (!radeon_hpd_sense(rdev, radeon_connector->hpd.hpd))
+		if (!radeon_hpd_sense(rdev, radeon_connector->hpd.hpd)) {
 			drm_helper_connector_dpms(connector, DRM_MODE_DPMS_OFF);
-		else if (radeon_dp_needs_link_train(radeon_connector))
+		} else if (radeon_dp_needs_link_train(radeon_connector)) {
+			/* force a mode on to trigger dp link training */
+			connector->dpms = DRM_MODE_DPMS_OFF;
 			drm_helper_connector_dpms(connector, DRM_MODE_DPMS_ON);
+		}
 		connector->dpms = saved_dpms;
 	}
 }
-- 
1.7.10.4