The optimization of energy consumption in mobile devices, particularly for resource-intensive applications such as mobile gaming, remains a critical and pervasive challenge. This paper presents a novel V-SYNC deadline-aware GPU dynamic voltage and frequency scaling (DVFS) governor designed to address this challenge by optimizing energy usage during gameplay. Our approach leverages V-SYNC events as deadlines for GPU frequency adjustments, minimizing energy wastage while ensuring timely frame rendering. To implement this strategy, we utilize the Perfetto software development kit for real-time system tracing and hardware counter capturing. This innovative approach enables fine-grained dynamic adjustment of GPU frequencies based on workload demands. The experimental results conducted on the Google Pixel 8 Pro demonstrate the efficacy of our proposed DVFS governor in achieving significant energy savings, with a reduction in per-frame energy consumption of up to 3%. Furthermore, our method enhances frame rate stability by reducing frame per second (FPS) variation by 37%, substantially improving the overall user experience. These experimental results substantiate the effectiveness of our methodology in achieving a balance between energy efficiency and performance in mobile gaming.