drm/i915: Capture max frl rate for PCON in dfp cap structure

HDMI2.1 PCON advertises Max FRL bandwidth supported by the PCON.

This patch captures this in dfp cap structure in intel_dp and uses
this to prune connector modes that cannot be supported by the PCON
and FRL bandwidth.

v2: Addressed review comments from Uma Shankar:
-tweaked the comparison of target bw and pcon frl bw to avoid roundup errors.
-minor modification of field names and comments.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201218103723.30844-9-ankit.k.nautiyal@intel.com

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -1432,6 +1432,7 @@ struct intel_dp {
 	struct {
 		int min_tmds_clock, max_tmds_clock;
 		int max_dotclock;
+		int pcon_max_frl_bw;
 		u8 max_bpc;
 		bool ycbcr_444_to_420;
 	} dfp;

drivers/gpu/drm/i915/display/intel_dp.c

@@ -716,6 +716,25 @@ intel_dp_mode_valid_downstream(struct intel_connector *connector,
 	const struct drm_display_info *info = &connector->base.display_info;
 	int tmds_clock;
 
+	/* If PCON supports FRL MODE, check FRL bandwidth constraints */
+	if (intel_dp->dfp.pcon_max_frl_bw) {
+		int target_bw;
+		int max_frl_bw;
+		int bpp = intel_dp_mode_min_output_bpp(&connector->base, mode);
+
+		target_bw = bpp * target_clock;
+
+		max_frl_bw = intel_dp->dfp.pcon_max_frl_bw;
+
+		/* converting bw from Gbps to Kbps*/
+		max_frl_bw = max_frl_bw * 1000000;
+
+		if (target_bw > max_frl_bw)
+			return MODE_CLOCK_HIGH;
+
+		return MODE_OK;
+	}
+
 	if (intel_dp->dfp.max_dotclock &&
 	    target_clock > intel_dp->dfp.max_dotclock)
 		return MODE_CLOCK_HIGH;
@@ -6480,13 +6499,18 @@ intel_dp_update_dfp(struct intel_dp *intel_dp,
 						 intel_dp->downstream_ports,
 						 edid);
 
+	intel_dp->dfp.pcon_max_frl_bw =
+		drm_dp_get_pcon_max_frl_bw(intel_dp->dpcd,
+					   intel_dp->downstream_ports);
+
 	drm_dbg_kms(&i915->drm,
-		    "[CONNECTOR:%d:%s] DFP max bpc %d, max dotclock %d, TMDS clock %d-%d\n",
+		    "[CONNECTOR:%d:%s] DFP max bpc %d, max dotclock %d, TMDS clock %d-%d, PCON Max FRL BW %dGbps\n",
 		    connector->base.base.id, connector->base.name,
 		    intel_dp->dfp.max_bpc,
 		    intel_dp->dfp.max_dotclock,
 		    intel_dp->dfp.min_tmds_clock,
-		    intel_dp->dfp.max_tmds_clock);
+		    intel_dp->dfp.max_tmds_clock,
+		    intel_dp->dfp.pcon_max_frl_bw);
 }
 
 static void
@@ -6578,6 +6602,8 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
 	intel_dp->dfp.min_tmds_clock = 0;
 	intel_dp->dfp.max_tmds_clock = 0;
 
+	intel_dp->dfp.pcon_max_frl_bw = 0;
+
 	intel_dp->dfp.ycbcr_444_to_420 = false;
 	connector->base.ycbcr_420_allowed = false;
 }