Gyro calibration in android?

Hi, I have attached gyro script to my camera's rotation and rotation works fine till +-90 degree in left or right(x axis) and after that camera rotates to -y even if i move in x axis.

Here is code

 void Start() {
 
      camera.transform.eulerAngles = Vector3(90,90,0); 
      if (Screen.orientation == ScreenOrientation.LandscapeLeft) 
             quatMult = Quaternion(0,0,-0.7071,0.7071); 
 
 } 
 
 void Update() { 
 
         quatMap = Quaternion(gyro.attitude.w,gyro.attitude.x,gyro.attitude.y,gyro.attitude.z);
         camera.transform.localRotation = quatMap * quatMult;
 
 }