drm/edid: parse HDMI 2.1 gaming (ALLM/VRR) capabilities from HF-VSDB

Parse the HDMI 2.1 gaming-related capabilities advertised in the HDMI
Forum VSDB (HF-VSDB) and expose them through struct drm_hdmi_info so
drivers can consume them.

Add struct drm_hdmi_vrr_cap describing the sink's VRR capabilities: Fast
VActive (Quick Frame Transport), Negative M VRR, Cinema VRR, MDelta, and
the VRRmin/VRRmax range, together with a "supported" flag derived from
that range. Add the fapa_start_location and allm (Auto Low Latency Mode)
flags to struct drm_hdmi_info.

drm_parse_hdmi_gaming_info() reads byte 8 of the HF-VSDB for the
FAPA/ALLM/FVA/CNMVRR/CinemaVRR/MDelta flags and bytes 9-10 for
VRRmin/VRRmax. Per HDMI 2.1, VRR is considered supported when VRRmin is
within 1-48 and VRRmax is either 0 (maximum based on the video mode) or
>= 100. It is invoked from drm_parse_hdmi_forum_scds(), and the parsed
values are logged for debugging.

Signed-off-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
Signed-off-by: Tomasz Pakuła <tomasz.pakula.oficjalny@gmail.com>
Tested-by: Bernhard Berger <bernhard.berger@gmail.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Link: https://patch.msgid.link/20260730171754.704049-2-jerry.zuo@amd.com

2 files changed, 89 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 98dd72d986d5..9990a836d0b6 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -6210,6 +6210,33 @@ static void drm_parse_ycbcr420_deep_color_info(struct drm_connector *connector,
 	hdmi->y420_dc_modes = dc_mask;
 }
 
+static void drm_parse_hdmi_gaming_info(struct drm_hdmi_info *hdmi, const u8 *db)
+{
+	struct drm_hdmi_vrr_cap *vrr = &hdmi->vrr_cap;
+
+	if (cea_db_payload_len(db) < 8)
+		return;
+
+	hdmi->fapa_start_location = db[8] & DRM_EDID_FAPA_START_LOCATION;
+	hdmi->allm = db[8] & DRM_EDID_ALLM;
+	vrr->fva = db[8] & DRM_EDID_FVA;
+	vrr->cnmvrr = db[8] & DRM_EDID_CNMVRR;
+	vrr->cinema_vrr = db[8] & DRM_EDID_CINEMA_VRR;
+	vrr->mdelta = db[8] & DRM_EDID_MDELTA;
+
+	if (cea_db_payload_len(db) < 9)
+		return;
+
+	vrr->vrr_min = db[9] & DRM_EDID_VRR_MIN_MASK;
+	vrr->supported = (vrr->vrr_min > 0 && vrr->vrr_min <= 48);
+
+	if (cea_db_payload_len(db) < 10)
+		return;
+
+	vrr->vrr_max = (db[9] & DRM_EDID_VRR_MAX_UPPER_MASK) << 2 | db[10];
+	vrr->supported &= (vrr->vrr_max == 0 || vrr->vrr_max >= 100);
+}
+
 static void drm_parse_dsc_info(struct drm_hdmi_dsc_cap *hdmi_dsc,
 			       const u8 *hf_scds)
 {
@@ -6336,6 +6363,8 @@ static void drm_parse_hdmi_forum_scds(struct drm_connector *connector,
 
 	drm_parse_ycbcr420_deep_color_info(connector, hf_scds);
 
+	drm_parse_hdmi_gaming_info(&connector->display_info.hdmi, hf_scds);
+
 	if (cea_db_payload_len(hf_scds) >= 11 && hf_scds[11]) {
 		drm_parse_dsc_info(hdmi_dsc, hf_scds);
 		dsc_support = true;
@@ -6345,6 +6374,19 @@ static void drm_parse_hdmi_forum_scds(struct drm_connector *connector,
 		    "[CONNECTOR:%d:%s] HF-VSDB: max TMDS clock: %d KHz, HDMI 2.1 support: %s, DSC 1.2 support: %s\n",
 		    connector->base.id, connector->name,
 		    max_tmds_clock, str_yes_no(max_frl_rate), str_yes_no(dsc_support));
+	drm_dbg_kms(connector->dev,
+		    "[CONNECTOR:%d:%s] FAPA in blanking: %s, ALLM support: %s, Fast Vactive support: %s\n",
+		    connector->base.id, connector->name, str_yes_no(hdmi->fapa_start_location),
+		    str_yes_no(hdmi->allm), str_yes_no(hdmi->vrr_cap.fva));
+	drm_dbg_kms(connector->dev,
+		    "[CONNECTOR:%d:%s] Negative M VRR support: %s, CinemaVRR support: %s, Mdelta: %d\n",
+		    connector->base.id, connector->name, str_yes_no(hdmi->vrr_cap.cnmvrr),
+		    str_yes_no(hdmi->vrr_cap.cinema_vrr), hdmi->vrr_cap.mdelta);
+	drm_dbg_kms(connector->dev,
+		    "[CONNECTOR:%d:%s] VRRmin: %u, VRRmax: %u, VRR supported: %s\n",
+		    connector->base.id, connector->name, hdmi->vrr_cap.vrr_min,
+		    hdmi->vrr_cap.vrr_max, str_yes_no(hdmi->vrr_cap.supported));
+
 }
 
 static void drm_parse_hdmi_deep_color_info(struct drm_connector *connector,
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 48059e7073e5..c61345e6fb08 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -255,6 +255,44 @@ struct drm_scdc {
 };
 
 /**
+ * struct drm_hdmi_vrr_cap - Information about VRR capabilities of a HDMI sink
+ *
+ * Describes the VRR support provided by HDMI 2.1 sink. The information is
+ * fetched fom additional HFVSDB blocks defined for HDMI 2.1.
+ */
+struct drm_hdmi_vrr_cap {
+	/** @fva: flag for Fast VActive (Quick Frame Transport) support */
+	bool fva;
+
+	/** @mcnmvrr: flag for Negative M VRR support */
+	bool cnmvrr;
+
+	/** @mcinema_vrr: flag for Cinema VRR support */
+	bool cinema_vrr;
+
+	/** @mdelta: flag for limited frame-to-frame compensation support */
+	bool mdelta;
+
+	/**
+	 * @vrr_min : minimum supported variable refresh rate in Hz.
+	 * Valid values only inide 1 - 48 range
+	 */
+	u16 vrr_min;
+
+	/**
+	 * @vrr_max : maximum supported variable refresh rate in Hz (optional).
+	 * Valid values are either 0 (max based on video mode) or >= 100
+	 */
+	u16 vrr_max;
+
+	/**
+	 * @supported: flag for vrr support based on checking for VRRmin and
+	 * VRRmax values having correct values.
+	 */
+	bool supported;
+};
+
+/**
  * struct drm_hdmi_dsc_cap - DSC capabilities of HDMI sink
  *
  * Describes the DSC support provided by HDMI 2.1 sink.
@@ -330,6 +368,15 @@ struct drm_hdmi_info {
 	/** @max_lanes: supported by sink */
 	u8 max_lanes;
 
+	/** @fapa_start_location: flag for the FAPA in blanking support */
+	bool fapa_start_location;
+
+	/** @allm: flag for Auto Low Latency Mode support by sink */
+	bool allm;
+
+	/** @vrr_cap: VRR capabilities of the sink */
+	struct drm_hdmi_vrr_cap vrr_cap;
+
 	/** @dsc_cap: DSC capabilities of the sink */
 	struct drm_hdmi_dsc_cap dsc_cap;
 };