Commit 453b0016 authored by Wayne Lin's avatar Wayne Lin Committed by Alex Deucher
Browse files

drm/amd/display: Detect dpcd_rev when hotplug mst monitor 



[Why]
Once mst topology is constructed, later on new connected monitors
are reported to source by CSN message. Within CSN, there is no
carried info of DPCD_REV comparing to LINK_ADDRESS reply. As the
result, we might leave some ports connected to DP but without DPCD
revision number which will affect us determining the capability of
the DP Rx.

[How]
Send out remote DPCD read when the port's dpcd_rev is 0x0 in
detect_ctx(). Firstly, read out the value from DPCD 0x2200. If the
return value is 0x0, it's likely the DP1.2 DP Rx then we reques
revision from DPCD 0x0 again.

Reviewed-by: default avatarHersen Wu <hersenwu@amd.com>
Acked-by: default avatarHamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: default avatarWayne Lin <Wayne.Lin@amd.com>
Tested-by: default avatarDaniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 84de5c2e

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c

+37 −1
Original line number Diff line number Diff line
@@ -344,12 +344,48 @@ dm_dp_mst_detect(struct drm_connector *connector, 
{

	struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);

	struct amdgpu_dm_connector *master = aconnector->mst_port;

	struct drm_dp_mst_port *port = aconnector->port;

	int connection_status;



	if (drm_connector_is_unregistered(connector))

		return connector_status_disconnected;



	return drm_dp_mst_detect_port(connector, ctx, &master->mst_mgr,

	connection_status = drm_dp_mst_detect_port(connector, ctx, &master->mst_mgr,

				      aconnector->port);



	if (port->pdt != DP_PEER_DEVICE_NONE && !port->dpcd_rev) {

		uint8_t dpcd_rev;

		int ret;



		ret = drm_dp_dpcd_readb(&port->aux, DP_DP13_DPCD_REV, &dpcd_rev);



		if (ret == 1) {

			port->dpcd_rev = dpcd_rev;



			/* Could be DP1.2 DP Rx case*/

			if (!dpcd_rev) {

				ret = drm_dp_dpcd_readb(&port->aux, DP_DPCD_REV, &dpcd_rev);



				if (ret == 1)

					port->dpcd_rev = dpcd_rev;

			}



			if (!dpcd_rev)

				DRM_DEBUG_KMS("Can't decide DPCD revision number!");

		}



		/*

		 * Could be legacy sink, logical port etc on DP1.2.

		 * Will get Nack under these cases when issue remote

		 * DPCD read.

		 */

		if (ret != 1)

			DRM_DEBUG_KMS("Can't access DPCD");

	} else if (port->pdt == DP_PEER_DEVICE_NONE) {

		port->dpcd_rev = 0;

	}



	return connection_status;

}



static int dm_dp_mst_atomic_check(struct drm_connector *connector,