MCSX_PEX_RX_SLAVE_CUSTOM_TAGX
reg = (req->dir == MCS_RX) ? MCSX_PEX_RX_SLAVE_CUSTOM_TAGX(idx) :
reg = MCSX_PEX_RX_SLAVE_CUSTOM_TAGX(0);
reg = MCSX_PEX_RX_SLAVE_CUSTOM_TAGX(1);