When deploying deep neural networks (DNNs) onto deep learning processors, we usually exploit mixed-precision quantization and voltage-frequency scaling to make tradeoffs among accuracy, latency, and energy. Conventional methods usually determine the quantization-voltage-frequency (QVF) policy before DNNs are deployed onto local devices. However, they are difficult to make optimal customizations for local user scenarios. In this article, we solve the problem by enabling on-device QVF tuning with a new deep learning processor architecture Evolver. Evolver has a QVF tuning mode to deploy DNNs with local customizations before normal execution. In this mode, Evolver uses reinforcement learning to search the optimal QVF policy based on direct hardware feedbacks from the chip itself. After that, Evolver runs the newly quantized DNN inference under the searched voltage and frequency. To improve the performance and energy efficiency of both training and inference, we introduce bidirectional speculation and runtime reconfiguration techniques into the architecture. To the best of our knowledge, Evolver is the first deep learning processor that utilizes on-device QVF tuning to achieve both customized and optimal DNN deployment.