linux-kernel - [PATCH 11/17] drm/amd/display: Support HDMI VRRmax=0

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Message-ID: <20260119011146.62302-12-tomasz.pakula.oficjalny@gmail.com>
Date: Mon, 19 Jan 2026 02:11:40 +0100
From: Tomasz Pakuła <tomasz.pakula.oficjalny@...il.com>
To: alexander.deucher@....com,
	harry.wentland@....com,
	sunpeng.li@....com
Cc: maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org,
	tzimmermann@...e.de,
	airlied@...il.com,
	simona@...ll.ch,
	siqueira@...lia.com,
	dri-devel@...ts.freedesktop.org,
	amd-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	tomasz.pakula.oficjalny@...il.com,
	bernhard.berger@...il.com
Subject: [PATCH 11/17] drm/amd/display: Support HDMI VRRmax=0

[Why]
VRRmax=0 is a valid value and means that the upper bound is guared by
the selected video mode.

[How]
In this context, saved vrr max is the max possible refresh rate ever.
Try getting upper VRR bound from AMD vsdbif it exists or rely on the
limitations of BRR in VTEM info frames.

I found through testing, that TVs seem to reject VTEM when BRR is set
to over 1000 Hz. Use this as the last resort VRRmax.

Signed-off-by: Tomasz Pakuła <tomasz.pakula.oficjalny@...il.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 22 ++++++++++++++-----
 .../amd/display/modules/inc/mod_info_packet.h |  2 ++
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 772deaa136d7..3c535a361882 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -13194,17 +13194,29 @@ static void monitor_range_from_vsdb(struct drm_connector *conn,
 }
 
 /*
- * Get VRR range from HDMI VRR info in EDID.
+ * Get VRR range from HDMI VRR info in EDID. If VRRmax == 0,
+ * try getting upper bound from AMD vsdb (if passed).
  *
  * @conn: drm_connector with HDMI VRR info
+ * @vsdb: AMD vsdb from CAE. Can be NULL if not found.
  */
-static void monitor_range_from_hdmi(struct drm_connector *conn)
+static void monitor_range_from_hdmi(struct drm_connector *conn,
+				    const struct amdgpu_hdmi_vsdb_info *vsdb)
 {
 	struct drm_monitor_range_info *range = &conn->display_info.monitor_range;
 	struct drm_hdmi_vrr_cap *caps = &conn->display_info.hdmi.vrr_cap;
+	u16 vrr_max = caps->vrr_max;
+
+	/* Try getting upper vrr bound from AMD vsdb */
+	if (vrr_max == 0 && vsdb)
+		vrr_max = vsdb->max_refresh_rate_hz;
+
+	/* Use max possible BRR value as a last resort */
+	if (vrr_max == 0)
+		vrr_max = VTEM_BRR_MAX;
 
 	range->min_vfreq = caps->vrr_min;
-	range->max_vfreq = caps->vrr_max;
+	range->max_vfreq = vrr_max;
 }
 
 /**
@@ -13342,8 +13354,8 @@ void amdgpu_dm_update_freesync_caps(struct drm_connector *connector,
 	/* DP -> HDMI PCON */
 	} else if (pcon_allowed) {
 		/* Prefer HDMI VRR */
-		if (hdmi_vrr->supported && hdmi_vrr->vrr_max > 0)
-			monitor_range_from_hdmi(connector);
+		if (hdmi_vrr->supported)
+			monitor_range_from_hdmi(connector, valid_vsdb_cea ? &vsdb_info : NULL);
 		else if (vsdb_freesync) {
 			amdgpu_dm_connector->vsdb_info = vsdb_info;
 			monitor_range_from_vsdb(connector, &vsdb_info);
diff --git a/drivers/gpu/drm/amd/display/modules/inc/mod_info_packet.h b/drivers/gpu/drm/amd/display/modules/inc/mod_info_packet.h
index 5de8a6918e6a..67274ce129bd 100644
--- a/drivers/gpu/drm/amd/display/modules/inc/mod_info_packet.h
+++ b/drivers/gpu/drm/amd/display/modules/inc/mod_info_packet.h
@@ -33,6 +33,8 @@ struct dc_stream_state;
 struct dc_info_packet;
 struct mod_vrr_params;
 
+#define VTEM_BRR_MAX 1000
+
 void set_vsc_packet_colorimetry_data(
 		const struct dc_stream_state *stream,
 		struct dc_info_packet *info_packet,
-- 
2.52.0