Row Hammer is a serious security threat on DRAM that causes bit flips in nearby rows when a DRAM row is accessed frequently. Many mitigation strategies were proposed against Row Hammer attack, and some were adopted and implemented by the hardware vendors also. But even the latest generations of DRAM with in-DRAM mitigation were found vulnerable to Row Hammer attack. We perform security analysis on a recently proposed Row Hammer mitigation strategy named Graphene and show that it is still vulnerable to Row Hammer attack if a certain access pattern is followed. We propose to use Cache Pinning as a mitigation strategy against Row Hammer attack. Our experiments show an improvement in performance not just in the case of attack programs, but also the benign applications running in the system along with the attack program with the proposed design. We also propose new strategies that can be used to mitigate Row Hammer attack.