How should I use hinfsyn with MIMO controller?

I am trying to get a 3x3 diagonal controller to control a 3x3 transfer function matrix by using H-infinity synthesis. I have tried this simple code but it doesn't work:

 P = tf(rss(3,3,3));
systemnames = '[P(1,1) P(2,2) P(3,3)]';
inputvar = '[r(1);r(2);r(3);u(1);u(2);u(3)]';
outputvar = '[P(1,1)-r(1); P(2,2)-r(2); P(3,3)-r(3)]';
input_to_P = '[u(1); u(2);u(3)]';
sysoutname = '[P(1,1) P(2,2) P(3,3)]';
sysic;
[Khinf,CL,GAM,INFO] = hinfsyn(P,3,3,'DISPLAY','on')

Any working approach will be appreciated.