add fucntion to control tegra optimizations in run-time

modules/core/src/system.cpp

@@ -1257,6 +1257,36 @@ void setUseIPP(bool flag)
 
 } // namespace ipp
 
+#ifdef HAVE_TEGRA_OPTIMIZATION
+
+namespace tegra {
+
+bool useTegra()
+{
+    CoreTLSData* data = getCoreTlsData().get();
+
+    if (data->useTegra < 0)
+    {
+        const char* pTegraEnv = getenv("OPENCV_TEGRA");
+        if (pTegraEnv && (cv::String(pTegraEnv) == "disabled"))
+            data->useTegra = false;
+        else
+            data->useTegra = true;
+    }
+
+    return (data->useTegra > 0);
+}
+
+void setUseTegra(bool flag)
+{
+    CoreTLSData* data = getCoreTlsData().get();
+    data->useTegra = flag;
+}
+
+} // namespace tegra
+
+#endif
+
 } // namespace cv
 
 /* End of file. */