[PATCH v2 02/13] drm/hdcp: Avoid changing crtc state in hdcp atomic check

[Sean Paul]

From: Sean Paul <seanpaul at chromium.org>

Instead of forcing a modeset in the hdcp atomic check, simply return
true if the content protection value is changing and let the driver
decide whether a modeset is required or not.

Signed-off-by: Sean Paul <seanpaul at chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210913175747.47456-3-sean@poorly.run #v1

Changes in v2:
-None
---
 drivers/gpu/drm/drm_hdcp.c                  | 33 +++++++++++++++------
 drivers/gpu/drm/i915/display/intel_atomic.c |  5 ++--
 include/drm/drm_hdcp.h                      |  2 +-
 3 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/drm_hdcp.c b/drivers/gpu/drm/drm_hdcp.c
index 522326b03e66..dd8fa91c51d6 100644
--- a/drivers/gpu/drm/drm_hdcp.c
+++ b/drivers/gpu/drm/drm_hdcp.c
@@ -430,11 +430,14 @@ EXPORT_SYMBOL(drm_hdcp_update_content_protection);
  * @connector: drm_connector on which content protection state needs an update
  *
  * This function can be used by display drivers to perform an atomic check on the
- * hdcp state elements. If hdcp state has changed, this function will set
- * mode_changed on the crtc driving the connector so it can update its hardware
- * to match the hdcp state.
+ * hdcp state elements. If hdcp state has changed in a manner which requires the
+ * driver to enable or disable content protection, this function will return
+ * true.
+ *
+ * Returns:
+ * true if the driver must enable/disable hdcp, false otherwise
  */
-void drm_hdcp_atomic_check(struct drm_connector *connector,
+bool drm_hdcp_atomic_check(struct drm_connector *connector,
 			   struct drm_atomic_state *state)
 {
 	struct drm_connector_state *new_conn_state, *old_conn_state;
@@ -452,10 +455,12 @@ void drm_hdcp_atomic_check(struct drm_connector *connector,
 		 * If the connector is being disabled with CP enabled, mark it
 		 * desired so it's re-enabled when the connector is brought back
 		 */
-		if (old_hdcp == DRM_MODE_CONTENT_PROTECTION_ENABLED)
+		if (old_hdcp == DRM_MODE_CONTENT_PROTECTION_ENABLED) {
 			new_conn_state->content_protection =
 				DRM_MODE_CONTENT_PROTECTION_DESIRED;
-		return;
+			return true;
+		}
+		return false;
 	}
 
 	new_crtc_state = drm_atomic_get_new_crtc_state(state,
@@ -467,9 +472,19 @@ void drm_hdcp_atomic_check(struct drm_connector *connector,
 	*/
 	if (drm_atomic_crtc_needs_modeset(new_crtc_state) &&
 	    (old_hdcp == DRM_MODE_CONTENT_PROTECTION_ENABLED &&
-	     new_hdcp != DRM_MODE_CONTENT_PROTECTION_UNDESIRED))
+	     new_hdcp != DRM_MODE_CONTENT_PROTECTION_UNDESIRED)) {
 		new_conn_state->content_protection =
 			DRM_MODE_CONTENT_PROTECTION_DESIRED;
+		return true;
+	}
+
+	/*
+	 * Coming back from disable or changing CRTC with DESIRED state requires
+	 * that the driver try CP enable.
+	 */
+	if (new_hdcp == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
+	    new_conn_state->crtc != old_conn_state->crtc)
+		return true;
 
 	/*
 	 * Nothing to do if content type is unchanged and one of:
@@ -484,9 +499,9 @@ void drm_hdcp_atomic_check(struct drm_connector *connector,
 	     new_hdcp == DRM_MODE_CONTENT_PROTECTION_DESIRED)) {
 		if (old_conn_state->hdcp_content_type ==
 				new_conn_state->hdcp_content_type)
-			return;
+			return false;
 	}
 
-	new_crtc_state->mode_changed = true;
+	return true;
 }
 EXPORT_SYMBOL(drm_hdcp_atomic_check);
diff --git a/drivers/gpu/drm/i915/display/intel_atomic.c b/drivers/gpu/drm/i915/display/intel_atomic.c
index 1e306e8427ec..c7b5470c40aa 100644
--- a/drivers/gpu/drm/i915/display/intel_atomic.c
+++ b/drivers/gpu/drm/i915/display/intel_atomic.c
@@ -122,8 +122,6 @@ int intel_digital_connector_atomic_check(struct drm_connector *conn,
 		to_intel_digital_connector_state(old_state);
 	struct drm_crtc_state *crtc_state;
 
-	drm_hdcp_atomic_check(conn, state);
-
 	if (!new_state->crtc)
 		return 0;
 
@@ -139,7 +137,8 @@ int intel_digital_connector_atomic_check(struct drm_connector *conn,
 	    new_conn_state->base.picture_aspect_ratio != old_conn_state->base.picture_aspect_ratio ||
 	    new_conn_state->base.content_type != old_conn_state->base.content_type ||
 	    new_conn_state->base.scaling_mode != old_conn_state->base.scaling_mode ||
-	    !drm_connector_atomic_hdr_metadata_equal(old_state, new_state))
+	    !drm_connector_atomic_hdr_metadata_equal(old_state, new_state) ||
+	    drm_hdcp_atomic_check(conn, state))
 		crtc_state->mode_changed = true;
 
 	return 0;
diff --git a/include/drm/drm_hdcp.h b/include/drm/drm_hdcp.h
index d49977a042e1..e6e3d16bc7d3 100644
--- a/include/drm/drm_hdcp.h
+++ b/include/drm/drm_hdcp.h
@@ -301,7 +301,7 @@ int drm_connector_attach_content_protection_property(
 		struct drm_connector *connector, bool hdcp_content_type);
 void drm_hdcp_update_content_protection(struct drm_connector *connector,
 					u64 val);
-void drm_hdcp_atomic_check(struct drm_connector *connector,
+bool drm_hdcp_atomic_check(struct drm_connector *connector,
 			   struct drm_atomic_state *state);
 
 /* Content Type classification for HDCP2.2 vs others */
-- 
Sean Paul, Software Engineer, Google / Chromium OS