BPI-M2P Display hdmi Hsync problem

Hi to everyone, I setup the resolution of 1024x600 with disp_mode=69 using the kernel BPI-M2P-bsp-4.4 with some modifications. The problem is that when I plug the hdmi of m2p to any monitor I can see that the resolution 1024x600 working correct. Now with the same setting when I plug the hdmi of m2p with our lcd panel through an hdmi to rgb converter ic texas(TFP401) doesn’t work. I’m 100% sure that our lcd panel and hdmi to rgb converter work perfectly because if we put any other hdmi ouput device works correct. Trying to solve this problem i figured out that using oscilloscope I don’t get H sync pulses but instead I get a constant high level DC, however the V sync and Pixel clock frequency’s are the correct ones according to hdmi_core.c. I also set the auto_hpd=0 without any luck. Hope someone has a solution to this problem.