drm/amd/display: Fix unstable HPCP compliance on Chrome Barcelo

[Why]
Intermittently, there presents two occurrences of 0 stream
commits in a single HPD event. Current HDCP sequence does
not consider such scenerio, and will thus disable HDCP.

[How]
Add condition check to include stream remove and re-enable
case for HDCP enable.

Reviewed-by: Bhawanpreet Lakha <[e-mail]>
Acked-by: Mikita Lipski <[e-mail]>
Signed-off-by: Qingqing Zhuo <[e-mail]>
Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

···
 	    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
+	/* Stream removed and re-enabled
+	 *
+	 * Can sometimes overlap with the HPD case,
+	 * thus set update_hdcp to false to avoid
+	 * setting HDCP multiple times.
+	 *
+	 * Handles:	DESIRED -> DESIRED (Special case)
+	 */
+	if (!(old_state->crtc && old_state->crtc->enabled) &&
+		state->crtc && state->crtc->enabled &&
+		connector->state->content_protection == DRM_MODE_CONTENT_PROTECTION_DESIRED) {
+		dm_con_state->update_hdcp = false;
+		return true;
+	}
+
+	/* Hot-plug, headless s3, dpms
+	 *
+	 * Only start HDCP if the display is connected/enabled.
+	 * update_hdcp flag will be set to false until the next
+	 * HPD comes in.
 	 *
 	 * Handles:	DESIRED -> DESIRED (Special case)
 	 */