At first the I made a direct connection and it was 100 Frames per second loss. Now I added 49.9 Ohms and It became 100 times better (1 Frames per second loss, on some channels It 1 packet per our loss. The pcb traces are diff pairs with right impedance and matched length. I only have 200 MHz bandwidth oscilloscope and can't completely evaluate signal integrity, but generally it looks normal (like MLT-3), DC offcets are also fine (at least on DP83849IF side), does DC offsets even metter? KSZ9477S has internal biasing and termination... My question is how to acheave reliable communication in my case? Maybe I should play with capasitors and resistors values? What is the methology? Does it even possible to acheive relaible communication through AC coupling? I just found out that I have pretty bad ripples on 3.3V power supply rails (+- 200 mV, picture is attached) Can it make a difference?
So I've managed to solve the problem by doing three things: I've placed capacitive coupling (0.1 uF) between DP83849IF and KSZ9477S, also I've placed 49.9 pull ups on DP83849IF side, and the last thing I did was turning off autonegotiation on KSZ9477S chip. So now there is no packet loss.