[PATCH v4 07/27] drm/amd/display: Use bigger VRR range if found in AMD vsdb

[Tomasz Pakuła]

[Why]
Some monitors only expose their full VRR range in AMD vsdb for some
reason.

[How]
Compare exposed ranges and use the bigger one.
Only adjust lower limit if it doesn't support LFC

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4177
Signed-off-by: Tomasz Pakuła <tomasz.pakula.oficjalny@xxxxxxxxx>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)

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 b3bf5e0c19a5..f36059bb0324 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -13269,6 +13269,34 @@ static bool copy_range_to_amdgpu_connector(struct drm_connector *conn)
 	return is_freesync_capable(range);
 }
 
+static void extend_range_from_vsdb(struct drm_display_info *display,
+				   const struct amdgpu_hdmi_vsdb_info *vsdb)
+{
+	u16 vrr_min = display->monitor_range.min_vfreq;
+	u16 vrr_max = display->monitor_range.max_vfreq;
+
+	/* Always extend upper limit */
+	if (vsdb->max_refresh_rate_hz > vrr_max)
+		vrr_max = vsdb->max_refresh_rate_hz;
+
+	/*
+	 * Only extend lower limit if current one disables LFC.
+
+	 * During widespread testing, we found that some manufacturers probably
+	 * had issues with their monitors' lower VRR boundaries and adjusted
+	 * them up (Gigabyte X34GS with official range 48 - 180, AMD vsdb 48 -
+	 * 180 yet Monitor Ranges 55 - 180). After setting the lower boundary
+	 * from AMD vsdb, such monitors start having blanking issues.
+	 *
+	 * Work around that by not touching VRR min if it still supports LFC.
+	 */
+	if (vsdb->min_refresh_rate_hz < vrr_min && (vrr_min * 2 >= vrr_max))
+		vrr_min = vsdb->min_refresh_rate_hz;
+
+	display->monitor_range.min_vfreq = vrr_min;
+	display->monitor_range.max_vfreq = vrr_max;
+}
+
 /**
  * amdgpu_dm_update_freesync_caps - Update Freesync capabilities
  *
@@ -13339,6 +13367,9 @@ void amdgpu_dm_update_freesync_caps(struct drm_connector *connector,
 		if (is_monitor_range_invalid(connector))
 			monitor_range_from_vsdb(&connector->display_info, &vsdb_info);
 
+		/* Try extending range if found in AMD vsdb */
+		extend_range_from_vsdb(&connector->display_info, &vsdb_info);
+
 		if (dpcd_caps.allow_invalid_MSA_timing_param)
 			freesync_capable = copy_range_to_amdgpu_connector(connector);
 
-- 
2.53.0