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

[Maxime Ripard <mripard@kernel.org>]

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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@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
if you do, you'll need a lock.

Maxime

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