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

[Cristian Ciocaltea <cristian.ciocaltea@collabora.com>]

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;
+
+	/**
+	 * @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);
+
 	/**
 	 * @funcs: HDMI connector Control Functions
 	 */

-- 
2.54.0