drm/amd/display: Add comments to hdcp property change code

[Why]
These comments are helpful in understanding which case each if
statement handles.

[How]
Add comments for state transitions (9 possible cases)

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Zhan Liu <zhan.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 9df92c6..936979c 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -7238,26 +7238,35 @@ static bool is_content_protection_different(struct drm_connector_state *state,
        struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);
        struct dm_connector_state *dm_con_state = to_dm_connector_state(connector->state);
 
+       /* Handle: Type0/1 change */
        if (old_state->hdcp_content_type != state->hdcp_content_type &&
            state->content_protection != DRM_MODE_CONTENT_PROTECTION_UNDESIRED) {
                state->content_protection = DRM_MODE_CONTENT_PROTECTION_DESIRED;
                return true;
        }
 
-       /* CP is being re enabled, ignore this */
+       /* CP is being re enabled, ignore this
+        *
+        * Handles:     ENABLED -> DESIRED
+        */
        if (old_state->content_protection == DRM_MODE_CONTENT_PROTECTION_ENABLED &&
            state->content_protection == DRM_MODE_CONTENT_PROTECTION_DESIRED) {
                state->content_protection = DRM_MODE_CONTENT_PROTECTION_ENABLED;
                return false;
        }
 
-       /* S3 resume case, since old state will always be 0 (UNDESIRED) and the restored state will be ENABLED */
+       /* S3 resume case, since old state will always be 0 (UNDESIRED) and the restored state will be ENABLED
+        *
+        * Handles:     UNDESIRED -> ENABLED
+        */
        if (old_state->content_protection == DRM_MODE_CONTENT_PROTECTION_UNDESIRED &&
            state->content_protection == DRM_MODE_CONTENT_PROTECTION_ENABLED)
                state->content_protection = DRM_MODE_CONTENT_PROTECTION_DESIRED;
 
        /* Check if something is connected/enabled, otherwise we start hdcp but nothing is connected/enabled
         * hot-plug, headless s3, dpms
+        *
+        * Handles:     DESIRED -> DESIRED (Special case)
         */
        if (dm_con_state->update_hdcp && state->content_protection == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
            connector->dpms == DRM_MODE_DPMS_ON && aconnector->dc_sink != NULL) {
@@ -7265,12 +7274,25 @@ static bool is_content_protection_different(struct drm_connector_state *state,
                return true;
        }
 
+       /*
+        * Handles:     UNDESIRED -> UNDESIRED
+        *              DESIRED -> DESIRED
+        *              ENABLED -> ENABLED
+        */
        if (old_state->content_protection == state->content_protection)
                return false;
 
+       /*
+        * Handles:     UNDESIRED -> DESIRED
+        *              DESIRED -> UNDESIRED
+        *              ENABLED -> UNDESIRED
+        */
        if (state->content_protection != DRM_MODE_CONTENT_PROTECTION_ENABLED)
                return true;
 
+       /*
+        * Handles:     DESIRED -> ENABLED
+        */
        return false;
 }