Commit 4f01a687 authored by Michael Strauss's avatar Michael Strauss Committed by Alex Deucher
Browse files

drm/amd/display: Block UHBR Based On USB-C PD Cable ID 



[WHY]
Currently the absence of UHBR cable ID caps from USB-C PD does not block UHBR
rates. In situations where DPCD reports valid UHBR capability but USB-C PD
does not, such as using a USB-C to DP1.4 dongle connected to a native DP2.1
cable, link loss and lightup failures can be seen as a result.

Additionally, in edge cases where a platform supports cable ID but DMUB
doesn't correctly return cable ID caps, driver currently also allows UHBR.

[HOW]
Block UHBR rates over DP alt mode if cable id indicates no UHBR support.
Additionally, block UHBR rates if a cable ID supported platform receives no
reply from a DMUB cable id query.

Reviewed-by: default avatarWenjing Liu <wenjing.liu@amd.com>
Reviewed-by: default avatarOvidiu Bunea <ovidiu.bunea@amd.com>
Signed-off-by: default avatarMichael Strauss <michael.strauss@amd.com>
Signed-off-by: default avatarAurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: default avatarDaniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 0e719a40

drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c

+16 −6
Original line number Diff line number Diff line
@@ -1409,7 +1409,8 @@ static bool get_usbc_cable_id(struct dc_link *link, union dp_cable_id *cable_id) 


	if (!link->ctx->dmub_srv ||

			link->ep_type != DISPLAY_ENDPOINT_PHY ||

			link->link_enc->features.flags.bits.DP_IS_USB_C == 0)

			link->link_enc->features.flags.bits.DP_IS_USB_C == 0 ||

			link->link_enc->features.flags.bits.IS_DP2_CAPABLE == 0)

		return false;



	memset(&cmd, 0, sizeof(cmd));
@@ -1422,7 +1423,9 @@ static bool get_usbc_cable_id(struct dc_link *link, union dp_cable_id *cable_id) 
		cable_id->raw = cmd.cable_id.data.output_raw;

		DC_LOG_DC("usbc_cable_id = %d.\n", cable_id->raw);

	}

	return cmd.cable_id.header.ret_status == 1;



	ASSERT(cmd.cable_id.header.ret_status);

	return true;

}



static void retrieve_cable_id(struct dc_link *link)
@@ -2103,6 +2106,8 @@ struct dc_link_settings dp_get_max_link_cap(struct dc_link *link) 
	/* get max link encoder capability */

	if (link_enc)

		link_enc->funcs->get_max_link_cap(link_enc, &max_link_cap);

	else

		return max_link_cap;



	/* Lower link settings based on sink's link cap */

	if (link->reported_link_cap.lane_count < max_link_cap.lane_count)
@@ -2136,10 +2141,15 @@ struct dc_link_settings dp_get_max_link_cap(struct dc_link *link) 
	 */

	cable_max_link_rate = get_cable_max_link_rate(link);



	if (!link->dc->debug.ignore_cable_id &&

			cable_max_link_rate != LINK_RATE_UNKNOWN) {

		if (cable_max_link_rate < max_link_cap.link_rate)

			max_link_cap.link_rate = cable_max_link_rate;

	if (!link->dc->debug.ignore_cable_id) {

		if (cable_max_link_rate != LINK_RATE_UNKNOWN)

			// cable max link rate known

			max_link_cap.link_rate = MIN(max_link_cap.link_rate, cable_max_link_rate);

		else if (link_enc->funcs->is_in_alt_mode && link_enc->funcs->is_in_alt_mode(link_enc))

			// cable max link rate ambiguous, DP alt mode, limit to HBR3

			max_link_cap.link_rate = MIN(max_link_cap.link_rate, LINK_RATE_HIGH3);

		//else {}

			// cable max link rate ambiguous, DP, do nothing



		if (!link->dpcd_caps.cable_id.bits.UHBR13_5_CAPABILITY &&

				link->dpcd_caps.cable_id.bits.CABLE_TYPE >= 2)