[PATCH] drm/rockchip: dw_hdmi_qp: attach the HDMI Colorspace connector property

[Igor Paunovic <royalnet026@gmail.com>]

The HDMI connector framework already consumes conn_state->colorspace
when generating the AVI infoframe (drm_hdmi_avi_infoframe_colorimetry()
in drm_hdmi_state_helper.c), and drmm_connector_hdmi_init() attaches
HDR_OUTPUT_METADATA and max bpc for this connector. The Colorspace
property itself, however, is never created, so userspace has no way to
request BT.2020 colorimetry and wide-gamut/HDR output stays effectively
unavailable on RK3588 even though the rest of the plumbing is in place.

Compositors gate HDR on this: KWin (Plasma 6.x) requires the Colorspace
property alongside HDR_OUTPUT_METADATA and max bpc before it reports an
output as HDR/wide-gamut capable, so the HDR toggle never appears.

Create and attach the standard HDMI colorspace property right after the
bridge connector is initialised. Passing 0 selects the full HDMI
colorspace set defined by the DRM core.

Tested on an Orange Pi 5 Plus (RK3588) with Plasma 6.6 on the Collabora
rockchip-v7.0 tree, which carries the same gap: with the property
attached, kscreen-doctor reports both HDMI outputs as HDR and
wide-color-gamut capable, KWin exposes the HDR toggle, the property
switches to BT2020_RGB at 10 bpc when enabled (verified with modetest),
and browsers report an HDR display so streaming services serve native
smpte2084/bt2020 content.

Signed-off-by: Igor Paunovic <royalnet026@gmail.com>
---
--- a/drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c
@@ -603,6 +603,20 @@
 		return dev_err_probe(hdmi->dev, PTR_ERR(connector),
 				     "Failed to init bridge connector\n");
 
+	/*
+	 * Attach the HDMI Colorspace property. The HDMI connector framework
+	 * already consumes conn_state->colorspace for the AVI infoframe
+	 * (drm_hdmi_avi_infoframe_colorimetry()), and HDR_OUTPUT_METADATA and
+	 * max bpc are attached by drmm_connector_hdmi_init(), but without the
+	 * Colorspace property userspace cannot request BT.2020 signalling,
+	 * which keeps wide-gamut/HDR output unavailable. Passing 0 selects
+	 * the full HDMI colorspace set defined by the core.
+	 */
+	ret = drm_mode_create_hdmi_colorspace_property(connector, 0);
+	if (ret)
+		return ret;
+	drm_connector_attach_colorspace_property(connector);
+
 	return 0;
 }