[PATCH 5/5] drm/i915/dp: Fix FRL BW check for HDMI2.1 DFP

[Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>]

During FRL bandwidth  check for downstream HDMI2.1 sink,
the min BPC supported is incorrectly taken for DP, and the check does
not consider ybcr420 only modes.
This patch fixes the bandwidth calculation similar to the TMDS case, by
taking min 8Bpc and considering Ycbcr420 only modes.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 52 ++++++++++++++++++-------
 1 file changed, 39 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index f0a62f71904e..7f24f7633078 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -118,6 +118,7 @@ bool intel_dp_is_edp(struct intel_dp *intel_dp)
 static void intel_dp_unset_edid(struct intel_dp *intel_dp);
 static int intel_dp_dsc_compute_bpp(struct intel_dp *intel_dp, u8 dsc_max_bpc);
 static bool intel_dp_is_hdmi_2_1_sink(struct intel_dp *intel_dp);
+static int intel_dp_hdmi_sink_max_frl(struct intel_dp *intel_dp);
 
 static bool
 is_dfp_hdmi_sink_dsc_1_2(struct intel_dp *intel_dp)
@@ -917,6 +918,32 @@ intel_dp_tmds_clock_valid(struct intel_dp *intel_dp,
 	return MODE_OK;
 }
 
+static int
+intel_dp_frl_bw_valid(struct intel_dp *intel_dp, int target_clock,
+		      int bpc, bool ycbcr_420_only)
+{
+	int target_bw;
+	int max_frl_bw;
+	int bpp = bpc * 3;
+
+	if (ycbcr_420_only)
+		target_clock /= 2;
+
+	target_bw = bpp * target_clock;
+
+	/* check for MAX FRL BW for both PCON and HDMI2.1 sink */
+	max_frl_bw = min(intel_dp->dfp.pcon_max_frl_bw,
+			 intel_dp_hdmi_sink_max_frl(intel_dp));
+
+	/* 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;
+}
+
 static enum drm_mode_status
 intel_dp_mode_valid_downstream(struct intel_connector *connector,
 			       const struct drm_display_mode *mode,
@@ -925,23 +952,24 @@ intel_dp_mode_valid_downstream(struct intel_connector *connector,
 	struct intel_dp *intel_dp = intel_attached_dp(connector);
 	const struct drm_display_info *info = &connector->base.display_info;
 	enum drm_mode_status status;
-	bool ycbcr_420_only;
+	bool ycbcr_420_only = drm_mode_is_420_only(info, mode);
 
 	/* 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, mode);
-
-		target_bw = bpp * target_clock;
 
-		max_frl_bw = intel_dp->dfp.pcon_max_frl_bw;
+		/* Assume 8bpc for the HDMI2.1 FRL BW check */
+		status = intel_dp_frl_bw_valid(intel_dp, target_clock, 8, ycbcr_420_only);
 
-		/* converting bw from Gbps to Kbps*/
-		max_frl_bw = max_frl_bw * 1000000;
+		if (status != MODE_OK) {
+			if (ycbcr_420_only ||
+			    !connector->base.ycbcr_420_allowed ||
+			    !drm_mode_is_420_also(info, mode))
+				return status;
 
-		if (target_bw > max_frl_bw)
-			return MODE_CLOCK_HIGH;
+			status = intel_dp_frl_bw_valid(intel_dp, target_clock, 8, true);
+			if (status != MODE_OK)
+				return status;
+		}
 
 		return MODE_OK;
 	}
@@ -950,8 +978,6 @@ intel_dp_mode_valid_downstream(struct intel_connector *connector,
 	    target_clock > intel_dp->dfp.max_dotclock)
 		return MODE_CLOCK_HIGH;
 
-	ycbcr_420_only = drm_mode_is_420_only(info, mode);
-
 	/* Assume 8bpc for the DP++/HDMI/DVI TMDS clock check */
 	status = intel_dp_tmds_clock_valid(intel_dp, target_clock,
 					   8, ycbcr_420_only, true);
-- 
2.25.1