diff options
| -rw-r--r-- | drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c index e5ab751a5ca1..b0cfe21871e4 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c @@ -3020,7 +3020,7 @@ static enum dc_link_rate get_lttpr_max_link_rate(struct dc_link *link) static enum dc_link_rate get_cable_max_link_rate(struct dc_link *link) { - enum dc_link_rate cable_max_link_rate = LINK_RATE_HIGH3; + enum dc_link_rate cable_max_link_rate = LINK_RATE_UNKNOWN; if (link->dpcd_caps.cable_id.bits.UHBR10_20_CAPABILITY & DP_UHBR20) cable_max_link_rate = LINK_RATE_UHBR20; @@ -3083,15 +3083,29 @@ struct dc_link_settings dp_get_max_link_cap(struct dc_link *link) max_link_cap.link_spread = link->reported_link_cap.link_spread; - /* Lower link settings based on cable attributes */ + /* Lower link settings based on cable attributes + * Cable ID is a DP2 feature to identify max certified link rate that + * a cable can carry. The cable identification method requires both + * cable and display hardware support. Since the specs comes late, it is + * anticipated that the first round of DP2 cables and displays may not + * be fully compatible to reliably return cable ID data. Therefore the + * decision of our cable id policy is that if the cable can return non + * zero cable id data, we will take cable's link rate capability into + * account. However if we get zero data, the cable link rate capability + * is considered inconclusive. In this case, we will not take cable's + * capability into account to avoid of over limiting hardware capability + * from users. The max overall link rate capability is still determined + * after actual dp pre-training. Cable id is considered as an auxiliary + * method of determining max link bandwidth capability. + */ cable_max_link_rate = get_cable_max_link_rate(link); if (!link->dc->debug.ignore_cable_id && + cable_max_link_rate != LINK_RATE_UNKNOWN && cable_max_link_rate < max_link_cap.link_rate) max_link_cap.link_rate = cable_max_link_rate; - /* - * account for lttpr repeaters cap + /* account for lttpr repeaters cap * notes: repeaters do not snoop in the DPRX Capabilities addresses (3.6.3). */ if (dp_is_lttpr_present(link)) { |