diff --git a/docs/envvars.rst b/docs/envvars.rst
index 31d7e43886d..4dc615c172f 100644
--- a/docs/envvars.rst
+++ b/docs/envvars.rst
@@ -516,6 +516,12 @@ Intel driver environment variables
    ``do32``
       generate compute shader SIMD32 programs even if workgroup size
       doesn't exceed the SIMD16 limit
+   ``draw_bkp``
+      Add semaphore wait before/after draw call count.
+      ``INTEL_DEBUG_BKP_BEFORE_DRAW_COUNT`` or
+      ``INTEL_DEBUG_BKP_AFTER_DRAW_COUNT`` can control draw call number.
+      To make test wait forever, we need to set preempt_timeout_ms and
+      i915.enable_hangcheck to zero.
    ``fall``
       emit messages about performance issues (same as ``perf``)
    ``fs``