I'm having a problem trying to use hot plug from the display side. I can see elsewhere on the board that the signal to TX_HPD (W4 ) transitions with the connection to the display but I don't see an interrupt indication at 0xB8( Tx Main ) reg 0x96 bit 7 regardless of the mask set in 0x94 . 0xB8 reg 0x42 bit 6 always reads high even when the signal is low. Three separate boards show the same behavior. Is there some additional configuration that needs to take place to use HPD on the transmit side? Is there another recommended technique for Tx HPD?