[PATCH v6 03/10] drm/hdcp: Update property value on content type and user changes

[Mark Yacoub]

From: Sean Paul <seanpaul at chromium.org>

This patch updates the connector's property value in 2 cases which were
previously missed:

1- Content type changes. The value should revert back to DESIRED from
   ENABLED in case the driver must re-authenticate the link due to the
   new content type.

2- Userspace sets value to DESIRED while ENABLED. In this case, the
   value should be reset immediately to ENABLED since the link is
   actively being encrypted.

To accommodate these changes, I've split up the conditionals to make
things a bit more clear (as much as one can with this mess of state).

Acked-by: Jani Nikula <jani.nikula at intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
Reviewed-by: Abhinav Kumar <abhinavk at codeaurora.org>
Signed-off-by: Sean Paul <seanpaul at chromium.org>
Signed-off-by: Mark Yacoub <markyacoub at chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210913175747.47456-4-sean@poorly.run #v1
Link: https://patchwork.freedesktop.org/patch/msgid/20210915203834.1439-4-sean@poorly.run #v2
Link: https://patchwork.freedesktop.org/patch/msgid/20211001151145.55916-4-sean@poorly.run #v3
Link: https://patchwork.freedesktop.org/patch/msgid/20211105030434.2828845-4-sean@poorly.run #v4
Link: https://patchwork.freedesktop.org/patch/msgid/20220411204741.1074308-4-sean@poorly.run

Changes in v2:
-None
Changes in v3:
-Fixed indentation issue identified by 0-day
Changes in v4:
-None
Changes in v5:
-None
Changes in v6:
-Rebased: modifications in drm_hdcp_helper.c instead of drm_hdcp.c

---
 drivers/gpu/drm/display/drm_hdcp_helper.c | 29 +++++++++++++++--------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_hdcp_helper.c b/drivers/gpu/drm/display/drm_hdcp_helper.c
index a3896b0904b5..ce92f1cac251 100644
--- a/drivers/gpu/drm/display/drm_hdcp_helper.c
+++ b/drivers/gpu/drm/display/drm_hdcp_helper.c
@@ -485,21 +485,30 @@ bool drm_hdcp_atomic_check(struct drm_connector *connector,
 		return true;
 
 	/*
-	 * Nothing to do if content type is unchanged and one of:
-	 *  - state didn't change
-	 *  - HDCP was activated since the last commit
-	 *  - attempting to set to desired while already enabled
+	 * Content type changes require an HDCP disable/enable cycle.
 	 */
-	if (old_hdcp == new_hdcp ||
-	    (old_hdcp == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
+	if (new_conn_state->hdcp_content_type !=
+	    old_conn_state->hdcp_content_type) {
+		new_conn_state->content_protection =
+			DRM_MODE_CONTENT_PROTECTION_DESIRED;
+		return true;
+	}
+
+	/*
+	 * Ignore meaningless state changes:
+ 	 *  - HDCP was activated since the last commit
+	 *  - Attempting to set to desired while already enabled
+ 	 */
+	if ((old_hdcp == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
 	     new_hdcp == DRM_MODE_CONTENT_PROTECTION_ENABLED) ||
 	    (old_hdcp == DRM_MODE_CONTENT_PROTECTION_ENABLED &&
 	     new_hdcp == DRM_MODE_CONTENT_PROTECTION_DESIRED)) {
-		if (old_conn_state->hdcp_content_type ==
-		    new_conn_state->hdcp_content_type)
-			return false;
+		new_conn_state->content_protection =
+			DRM_MODE_CONTENT_PROTECTION_ENABLED;
+		return false;
 	}
 
-	return true;
+	/* Finally, if state changes, we need action */
+	return old_hdcp != new_hdcp;
 }
 EXPORT_SYMBOL(drm_hdcp_atomic_check);
-- 
2.39.0.246.g2a6d74b583-goog