Stock ROM: Samsung Galaxy S5 SM-G9009W Android 6.0.1 Marshmallow. The firmware available for downloading https://www.sammobile.com/firmwares/database/SM-G9009W/. You can download your Samsung Galaxy S5 SM-G9009W firmware at the page, available for some countries. How to Root for Samsung Galaxy S5 SM-G9009W is the separated post, this post only for upgrading to Android 6.0.1 Marshmallow.
Tags: Android 6.0.1 Marshmallow, firmware update, Galaxy S5 SM-G9009W, stock rom