[PATCH v6 02/22] drm/connector: Add HDMI 2.0 scrambler infrastructure

[Maxime Ripard]

Hi,

Thanks for working on this!

On Wed, May 20, 2026 at 09:38:13PM +0300, Cristian Ciocaltea wrote:
> Add the connector-level infrastructure to support HDMI 2.0 scrambling:
> 
> - .scrambler_src_{enable|disable}() callbacks in
>   drm_connector_hdmi_funcs for source-side scrambling control
> - A delayed work item (scdc_work) with an associated callback (scdc_cb)
>   for periodic monitoring of sink-side scrambling status
> - A scrambler_enabled flag to track whether scrambling is currently
>   active
> 
> 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 | 14 +++++++++++
>  include/drm/drm_connector.h     | 52 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 66 insertions(+)

So we would need kunit tests for this.

> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 3fa4d2082cd7..91e58362fbc0 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;
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 5ad62c207d00..49eaa30b1329 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>
> @@ -1358,6 +1359,36 @@ struct drm_connector_hdmi_funcs {
>  	 */
>  	const struct drm_edid *(*read_edid)(struct drm_connector *connector);
>  
> +	/**
> +	 * @scrambler_src_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_src_enable callback is mandatory if HDMI 2.0 is
> +	 * to be supported.
> +	 *
> +	 * Returns:
> +	 * 0 on success, a negative error code otherwise
> +	 */
> +	int (*scrambler_src_enable)(struct drm_connector *connector);
> +
> +	/**
> +	 * @scrambler_src_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_src_disable callback is mandatory if HDMI 2.0 is
> +	 * to be supported.
> +	 *
> +	 * Returns:
> +	 * 0 on success, a negative error code otherwise
> +	 */
> +	int (*scrambler_src_disable)(struct drm_connector *connector);
> +
>  	/**
>  	 * @avi:
>  	 *
> @@ -1944,6 +1975,27 @@ struct drm_connector_hdmi {
>  	 */
>  	unsigned long supported_formats;
>  
> +	/**
> +	 * @scrambler_enabled: Tracks whether HDMI 2.0 scrambler is currently enabled.
> +	 */
> +	bool scrambler_enabled;
> +
> +	/**
> +	 * @scdc_work: Work item currently used to monitor sink-side scrambling
> +	 * status and retry setup if the sink resets it.
> +	 */
> +	struct delayed_work scdc_work;
> +
> +	/** @scdc_cb: Callback to be invoked as part of @scdc_work.
> +	 *
> +	 * Currently used to monitor sink-side scrambling status and retry
> +	 * setup if the sink resets it.
> +	 *
> +	 * This is assigned by the framework when making use of
> +	 * drm_scdc_start_scrambling() helper.
> +	 */
> +	void (*scdc_cb)(struct drm_connector *connector);
> +

I'm really not sure what the monitor thing is about. If we have setup
the scrambler at enable time, and we set it again on hotplugging, why
would we need to monitor anything?

Also, scrambling is only relevant for HDMI 2.0. We need a way to expose
that somehow and make sure that HDMI 2.0 drivers actually have
scrambling setup.

Maxime
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