what output resolution do you use? could you share your detailed operation?
lcd_xsize = 800;
lcd_ysize = 480;
left_margin = 39;
right_margin = 40;
upper_margin = 19;
lower_margin = 16;
hsync_len = 7;
vsync_len = 4;
mx53 can support 800x480 output, did you use the new lcd ? and pls check if your hardware connection is ok.