[PATCH v7 02/30] drm/connector: Add HDMI 2.0 scrambler infrastructure

Maxime Ripard mripard at kernel.org
Fri Jun 19 05:44:11 PDT 2026 

On Fri, Jun 12, 2026 at 09:11:54PM +0300, Cristian Ciocaltea wrote:
> Hi Maxime,
> 
> Thanks for taking the time to review this!
> 
> On 6/12/26 3:06 PM, Maxime Ripard wrote:
> > On Tue, Jun 02, 2026 at 01:44:02AM +0300, Cristian Ciocaltea wrote:
> >> Add the connector-level infrastructure to support HDMI 2.0 scrambling:
> >>
> >> - A scrambler_supported flag to indicate whether the source supports the
> >>   scrambling capability, in which case the newly introduced
> >>   .scrambler_{enable|disable}() callbacks in drm_connector_hdmi_funcs
> >>   are mandatory
> >> - A scrambler_needed flag to be managed by the hdmi state helpers based
> >>   on the negotiated TMDS character rate and the source/sink scrambling
> >>   capabilities
> >> - A scrambler_enabled flag to track whether scrambling is currently
> >>   active
> >> - A delayed work item (scdc_work) with an associated callback (scdc_cb)
> >>   to monitor sink-side scrambling status and retry the setup if the sink
> >>   resets it
> >>
> >> These are intended to be used by SCDC scrambling helpers to coordinate
> >> scrambling setup and teardown between the source driver and the DRM
> >> core.
> >>
> >> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea at collabora.com>
> >> ---
> >>  drivers/gpu/drm/drm_connector.c | 18 +++++++++
> >>  include/drm/drm_connector.h     | 81 +++++++++++++++++++++++++++++++++++++++++
> >>  2 files changed, 99 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> >> index a5d13b92b665..526dc2931b8a 100644
> >> --- a/drivers/gpu/drm/drm_connector.c
> >> +++ b/drivers/gpu/drm/drm_connector.c
> >> @@ -220,6 +220,19 @@ void drm_connector_free_work_fn(struct work_struct *work)
> >>  	}
> >>  }
> >>  
> >> +static void drm_connector_hdmi_scdc_work(struct work_struct *work)
> >> +{
> >> +	struct drm_connector *connector;
> >> +	struct drm_connector_hdmi *hdmi;
> >> +
> >> +	hdmi = container_of(to_delayed_work(work), struct drm_connector_hdmi,
> >> +			    scdc_work);
> >> +	connector = container_of(hdmi, struct drm_connector, hdmi);
> >> +
> >> +	if (hdmi->scdc_cb)
> >> +		hdmi->scdc_cb(connector);
> >> +}
> >> +
> >>  static int drm_connector_init_only(struct drm_device *dev,
> >>  				   struct drm_connector *connector,
> >>  				   const struct drm_connector_funcs *funcs,
> >> @@ -285,6 +298,7 @@ static int drm_connector_init_only(struct drm_device *dev,
> >>  	mutex_init(&connector->edid_override_mutex);
> >>  	mutex_init(&connector->hdmi.infoframes.lock);
> >>  	mutex_init(&connector->hdmi_audio.lock);
> >> +	INIT_DELAYED_WORK(&connector->hdmi.scdc_work, drm_connector_hdmi_scdc_work);
> >>  	connector->edid_blob_ptr = NULL;
> >>  	connector->epoch_counter = 0;
> >>  	connector->tile_blob_ptr = NULL;
> >> @@ -606,6 +620,10 @@ int drmm_connector_hdmi_init(struct drm_device *dev,
> >>  	    !hdmi_funcs->hdmi.write_infoframe)
> >>  		return -EINVAL;
> >>  
> >> +	if (connector->hdmi.scrambler_supported &&
> >> +	    (!hdmi_funcs->scrambler_enable || !hdmi_funcs->scrambler_disable))
> >> +		return -EINVAL;
> >> +
> >>  	ret = drmm_connector_init(dev, connector, funcs, connector_type, ddc);
> >>  	if (ret)
> >>  		return ret;
> >> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> >> index 529755c2e862..f1c5c15a6cce 100644
> >> --- a/include/drm/drm_connector.h
> >> +++ b/include/drm/drm_connector.h
> >> @@ -28,6 +28,7 @@
> >>  #include <linux/ctype.h>
> >>  #include <linux/hdmi.h>
> >>  #include <linux/notifier.h>
> >> +#include <linux/workqueue.h>
> >>  #include <drm/drm_mode_object.h>
> >>  #include <drm/drm_util.h>
> >>  #include <drm/drm_property.h>
> >> @@ -1057,6 +1058,19 @@ struct drm_connector_hdmi_state {
> >>  	 * @tmds_char_rate: TMDS Character Rate, in Hz.
> >>  	 */
> >>  	unsigned long long tmds_char_rate;
> >> +
> >> +	/**
> >> +	 * @scrambler_needed: Whether HDMI 2.0 SCDC scrambling is required
> >> +	 * for the negotiated mode/bpc/format.
> >> +	 *
> >> +	 * Computed by drm_atomic_helper_connector_hdmi_check() from
> >> +	 * @tmds_char_rate and the source/sink scrambling capabilities.
> >> +	 *
> >> +	 * Per HDMI 2.0, scrambling is mandatory above 340 MHz TMDS
> >> +	 * character rate. Optional scrambling at lower rates is
> >> +	 * deliberately not requested by the helper.
> >> +	 */
> >> +	bool scrambler_needed;
> >>  };
> >>  
> >>  /**
> >> @@ -1358,6 +1372,36 @@ struct drm_connector_hdmi_funcs {
> >>  	 */
> >>  	const struct drm_edid *(*read_edid)(struct drm_connector *connector);
> >>  
> >> +	/**
> >> +	 * @scrambler_enable:
> >> +	 *
> >> +	 * This callback is invoked through @drm_scdc_start_scrambling during
> >> +	 * a commit to setup SCDC scrambling and high TMDS clock ratio on
> >> +	 * source side.
> >> +	 *
> >> +	 * The @scrambler_enable callback is mandatory if HDMI 2.0 is to be
> >> +	 * supported.
> >> +	 *
> >> +	 * Returns:
> >> +	 * 0 on success, a negative error code otherwise
> >> +	 */
> >> +	int (*scrambler_enable)(struct drm_connector *connector);
> >> +
> >> +	/**
> >> +	 * @scrambler_disable:
> >> +	 *
> >> +	 * This callback is invoked through @drm_scdc_stop_scrambling during
> >> +	 * a commit to disable SCDC scrambling and high TMDS clock ratio on
> >> +	 * source side.
> >> +	 *
> >> +	 * The @scrambler_disable callback is mandatory if HDMI 2.0 is to be
> >> +	 * supported.
> >> +	 *
> >> +	 * Returns:
> >> +	 * 0 on success, a negative error code otherwise
> >> +	 */
> >> +	int (*scrambler_disable)(struct drm_connector *connector);
> >> +
> >>  	/**
> >>  	 * @avi:
> >>  	 *
> >> @@ -1960,6 +2004,43 @@ struct drm_connector_hdmi {
> >>  	 */
> >>  	unsigned long supported_formats;
> >>  
> >> +	/**
> >> +	 * @scrambler_supported: Indicates whether the HDMI controller
> >> +	 * (source) supports HDMI 2.0 SCDC scrambling.
> >> +	 *
> >> +	 * When true, @drm_connector_hdmi_funcs.scrambler_enable and
> >> +	 * @drm_connector_hdmi_funcs.scrambler_disable are mandatory.
> >> +	 * This is enforced by drmm_connector_hdmi_init().
> >> +	 *
> >> +	 * For HDMI bridge based drivers using drm_bridge_connector_init(),
> >> +	 * this is propagated automatically from bridges that set the
> >> +	 * DRM_BRIDGE_OP_HDMI_SCRAMBLER flag in their &drm_bridge->ops.
> >> +	 * Other drivers must set this field on @connector->hdmi before calling
> >> +	 * drmm_connector_hdmi_init().
> >> +	 */
> >> +	bool scrambler_supported;
> >> +
> >> +	/**
> >> +	 * @scrambler_enabled: Tracks whether HDMI 2.0 scrambler is currently enabled.
> >> +	 */
> >> +	bool scrambler_enabled;
> > 
> > This is already in the state. Why do you need to copy it over here, and
> 
> This was supposed to be used exclusively by drm_scdc_{start,stop}_scrambling()
> and drm_scdc_sync_status() helpers to control the work item and conditionally
> trigger CRTC resets.  However, it's now also set by vc4_hdmi_connector_init() to
> force disable the scrambler in the vc4_crtc_disable_at_boot() execution path.

Oh, my bad, I misread. I thought it was meant to be a copy of
scrambler_needed, but yeah, you're right it makes sense to keep it as is
and you can ignore this comment.

Maxime
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