drm/amd/display: allow DP40 cables to do UHBR13.5

why:
With DP2.1a expansion we are allowing DP40 cables to do UHBR13.5

how:
Assume UHBR10 means UHBR13.5 also for unknown cable type and
passive cable type.

Reviewed-by: George Shen <george.shen@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Ran Shi <ran.shi@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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 db87aa7b5c90f673f92251d380dd1b26abf06958..3c5334cdb3fb942b8e16a47a13097ba4e573c363 100644 (file)
--- 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
@@ -412,12 +412,18 @@ static enum dc_link_rate get_cable_max_link_rate(struct dc_link *link)
 {
        enum dc_link_rate cable_max_link_rate = LINK_RATE_UNKNOWN;
 
-       if (link->dpcd_caps.cable_id.bits.UHBR10_20_CAPABILITY & DP_UHBR20)
+       if (link->dpcd_caps.cable_id.bits.UHBR10_20_CAPABILITY & DP_UHBR20) {
                cable_max_link_rate = LINK_RATE_UHBR20;
-       else if (link->dpcd_caps.cable_id.bits.UHBR13_5_CAPABILITY)
+       } else if (link->dpcd_caps.cable_id.bits.UHBR13_5_CAPABILITY) {
                cable_max_link_rate = LINK_RATE_UHBR13_5;
-       else if (link->dpcd_caps.cable_id.bits.UHBR10_20_CAPABILITY & DP_UHBR10)
-               cable_max_link_rate = LINK_RATE_UHBR10;
+       } else if (link->dpcd_caps.cable_id.bits.UHBR10_20_CAPABILITY & DP_UHBR10) {
+               // allow DP40 cables to do UHBR13.5 for passive or unknown cable type
+               if (link->dpcd_caps.cable_id.bits.CABLE_TYPE < 2) {
+                       cable_max_link_rate = LINK_RATE_UHBR13_5;
+               } else {
+                       cable_max_link_rate = LINK_RATE_UHBR10;
+               }
+       }
 
        return cable_max_link_rate;
 }