From: Michael Strauss michael.strauss@amd.com
[ Upstream commit 4f01a68751194d05280d659a65758c09e4af04d6 ]
[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: Wenjing Liu wenjing.liu@amd.com Reviewed-by: Ovidiu Bunea ovidiu.bunea@amd.com Signed-off-by: Michael Strauss michael.strauss@amd.com Signed-off-by: Aurabindo Pillai aurabindo.pillai@amd.com Tested-by: Daniel Wheeler daniel.wheeler@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com Signed-off-by: Sasha Levin sashal@kernel.org --- .../dc/link/protocols/link_dp_capability.c | 22 ++++++++++++++----- 1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c index 60015e94c4aa8..ae6d7e3d117e2 100644 --- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c +++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c @@ -1402,7 +1402,8 @@ 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)); @@ -1415,7 +1416,9 @@ 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) @@ -2087,6 +2090,8 @@ 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) @@ -2120,10 +2125,15 @@ 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)