When testing DP83822 for PMD compliance testing, it may be required to adjust the swing level of the device if the levels are outside the range. A first check would be to ensure the schematic and layout design are the most optimal for testing. If the design is fixed, a way to correct for this would be to utilize Reg 0x403. However, when using this register, it is important to implement a soft restart (Reg 0x1F = 0x4000) immediately after configuring the register to implement the changes made.
Please note that this register requires extended register access.