drm/i915/dp: Fix pipe BPP clamping due to HDR

The pipe BPP value shouldn't be set outside of the source's / sink's
valid pipe BPP range, ensure this when increasing the minimum pipe BPP
value to 30 due to HDR.

While at it debug print if the HDR mode was requested for a connector by
setting the corresponding HDR connector property. This indicates
if the requested HDR mode could not be enabled, since the selected
pipe BPP is below 30, due to a sink capability or link BW limit.

v2:
- Also handle the case where the sink could support the target 30 BPP
  only in DSC mode due to a BW limit, but the sink doesn't support DSC
  or 30 BPP as a DSC input BPP. (Chaitanya)
- Debug print the connector's HDR mode in the link config dump, to
  indicate if a BPP >= 30 required by HDR couldn't be reached. (Ankit)
- Add Closes: trailer. (Ankit)
- Don't print the 30 BPP-outside of valid BPP range debug message if
  the min BPP is already > 30 (and so a target BPP >= 30 required
  for HDR is ensured).

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/7052
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15503
Fixes: ba49a46 ("drm/i915/dp: Set min_bpp limit to 30 in HDR mode")
Cc: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Cc: <stable@vger.kernel.org> # v6.18+
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com> # v1
Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260209133817.395823-1-imre.deak@intel.com
(cherry picked from commit 08b7ef1)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

Author: ideak

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

@@ -2665,6 +2665,7 @@ intel_dp_compute_config_limits(struct intel_dp *intel_dp,
 			       bool dsc,
 			       struct link_config_limits *limits)
 {
+	struct intel_display *display = to_intel_display(intel_dp);
 	bool is_mst = intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP_MST);
 	struct intel_connector *connector =
 		to_intel_connector(conn_state->connector);
@@ -2677,8 +2678,7 @@ intel_dp_compute_config_limits(struct intel_dp *intel_dp,
 	limits->min_lane_count = intel_dp_min_lane_count(intel_dp);
 	limits->max_lane_count = intel_dp_max_lane_count(intel_dp);
 
-	limits->pipe.min_bpp = intel_dp_in_hdr_mode(conn_state) ? 30 :
-				intel_dp_min_bpp(crtc_state->output_format);
+	limits->pipe.min_bpp = intel_dp_min_bpp(crtc_state->output_format);
 	if (is_mst) {
 		/*
 		 * FIXME: If all the streams can't fit into the link with their
@@ -2694,6 +2694,19 @@ intel_dp_compute_config_limits(struct intel_dp *intel_dp,
 							respect_downstream_limits);
 	}
 
+	if (!dsc && intel_dp_in_hdr_mode(conn_state)) {
+		if (intel_dp_supports_dsc(intel_dp, connector, crtc_state) &&
+		    limits->pipe.max_bpp >= 30)
+			limits->pipe.min_bpp = max(limits->pipe.min_bpp, 30);
+		else
+			drm_dbg_kms(display->drm,
+				    "[CONNECTOR:%d:%s] Can't force 30 bpp for HDR (pipe bpp: %d-%d DSC-support: %s)\n",
+				    connector->base.base.id, connector->base.name,
+				    limits->pipe.min_bpp, limits->pipe.max_bpp,
+				    str_yes_no(intel_dp_supports_dsc(intel_dp, connector,
+								     crtc_state)));
+	}
+
 	if (dsc && !intel_dp_dsc_compute_pipe_bpp_limits(connector, limits))
 		return false;
 
@@ -2825,10 +2838,11 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
 	}
 
 	drm_dbg_kms(display->drm,
-		    "DP lane count %d clock %d bpp input %d compressed " FXP_Q4_FMT " link rate required %d available %d\n",
+		    "DP lane count %d clock %d bpp input %d compressed " FXP_Q4_FMT " HDR %s link rate required %d available %d\n",
 		    pipe_config->lane_count, pipe_config->port_clock,
 		    pipe_config->pipe_bpp,
 		    FXP_Q4_ARGS(pipe_config->dsc.compressed_bpp_x16),
+		    str_yes_no(intel_dp_in_hdr_mode(conn_state)),
 		    intel_dp_config_required_rate(pipe_config),
 		    intel_dp_max_link_data_rate(intel_dp,
 						pipe_config->port_clock,