drm/display: hdmi: Add HDMI 2.0 scrambling management helpers

Add helpers to manage the full lifecycle of HDMI 2.0 SCDC scrambling on
both source and sink sides:

- drm_hdmi_mode_needs_scrambling(): checks whether a mode, bits per
  component and output format combination requires scrambling, which is
  needed when the resulting TMDS character rate exceeds the HDMI 1.3
  maximum of 340 MHz

- drm_connector_hdmi_enable_scrambling(): configures SCDC scrambling and
  high TMDS clock ratio and starts a periodic work item that monitors
  the sink's SCDC scrambling status, retrying setup when the sink loses
  state

- drm_connector_hdmi_disable_scrambling(): tears down scrambling on both
  sides and cancels the monitoring work

- drm_connector_hdmi_sync_scdc(): triggers a CRTC reset on reconnection
  to restore SCDC state lost during sink disconnects within an active
  display pipeline

Tested-by: Maud Spierings <maud_spierings@hotmail.com>
Tested-by: Diederik de Haas <diederik@cknow-tech.com>  # NanoPC-T6 LTS, Rock 5B
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Tested-by: Igor Paunovic <royalnet026@gmail.com> # RK3588 Orange Pi 5 Plus, dual HDMI
Tested-by: Robin Räber <robin.raebi@gmail.com>
Link: https://patch.msgid.link/20260901-dw-hdmi-qp-scramb-v11-10-bc12954a0688@collabora.com
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/include/drm/display/drm_hdmi_helper.h b/include/drm/display/drm_hdmi_helper.h
index 9c31ed90516b..2cdd6e3bc090 100644
--- a/include/drm/display/drm_hdmi_helper.h
+++ b/include/drm/display/drm_hdmi_helper.h
@@ -8,6 +8,7 @@
 struct drm_connector;
 struct drm_connector_state;
 struct drm_display_mode;
+struct drm_modeset_acquire_ctx;
 enum drm_output_color_format;
 
 void
@@ -35,4 +36,18 @@ drm_hdmi_acr_get_n_cts(unsigned long long tmds_char_rate,
 		       unsigned int *out_n,
 		       unsigned int *out_cts);
 
+bool
+drm_hdmi_mode_needs_scrambling(const struct drm_display_mode *mode,
+			       unsigned int bpc, enum drm_output_color_format fmt);
+
+int
+drm_connector_hdmi_enable_scrambling(struct drm_connector *connector,
+				     const struct drm_connector_state *conn_state);
+int
+drm_connector_hdmi_disable_scrambling(struct drm_connector *connector);
+
+int
+drm_connector_hdmi_sync_scdc(struct drm_connector *connector, bool plugged,
+			     struct drm_modeset_acquire_ctx *ctx);
+
 #endif