On my custom hardware board (design based on sabresd) ，using PHY as AR8031, 1Gbps rate instability (forced 100M normal), observing RGMII waveform is very bad.
Signal setup time exceeded 4.3ns in 1Gbps mode, exceeding the design requirements of RGMII.
But once in the OS system, the accompanying PC network is forced to 1 Gbps, at this time the Gigabit network can work properly (ping 65500), at this time the RGMII setup time is less than 2 ns
Question: why does RGMII's signal establishment time change? Is it related to software? I checked IOMUXC_SW_MUX_CTL_PAD_RGMIIxx and did not change before and after entering the system.
Or hardware? Where is it possible?