change clock parent

Hello,

I would like to ask if anyone knows how to set clock parent

I need to set parent of mcasp4_fck (MCASP3) to be audio_dpll_ck .

I've tried to do the following: 

ret = clk_set_parent(clkp_mcasp3, clkp_audio_pll); <-- return -22

But it returnes EINVAL (-22)

Can anyone give a hint on this issue ?

Regards,

Ran