drm/i915/dp: read sink UHBR rates

See if sink supports DP 2.0 128b/132b channel encoding, and update sink
rates accordingly.

FIXME: Also take LTTPR 128b/132b into account.

v2: Add build-time check for ->sink_rates size (Ville)

Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/089d807e887d308c52c84cf58dfb6777de18872d.1629735412.git.jani.nikula@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index b21dac1..3a70172 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -141,6 +141,26 @@ static void intel_dp_set_sink_rates(struct intel_dp *intel_dp)
                intel_dp->sink_rates[i] = dp_rates[i];
        }
 
+       /*
+        * Sink rates for 128b/132b. If set, sink should support all 8b/10b
+        * rates and 10 Gbps.
+        */
+       if (intel_dp->dpcd[DP_MAIN_LINK_CHANNEL_CODING] & DP_CAP_ANSI_128B132B) {
+               u8 uhbr_rates = 0;
+
+               BUILD_BUG_ON(ARRAY_SIZE(intel_dp->sink_rates) < ARRAY_SIZE(dp_rates) + 3);
+
+               drm_dp_dpcd_readb(&intel_dp->aux,
+                                 DP_128B132B_SUPPORTED_LINK_RATES, &uhbr_rates);
+
+               if (uhbr_rates & DP_UHBR10)
+                       intel_dp->sink_rates[i++] = 1000000;
+               if (uhbr_rates & DP_UHBR13_5)
+                       intel_dp->sink_rates[i++] = 1350000;
+               if (uhbr_rates & DP_UHBR20)
+                       intel_dp->sink_rates[i++] = 2000000;
+       }
+
        intel_dp->num_sink_rates = i;
 }