GM_SERIAL_MODE
gma_write16(hw, port, GM_SERIAL_MODE, reg);
gma_write16(hw, port, GM_SERIAL_MODE, mode);
reg = gma_read16(sky2->hw, sky2->port, GM_SERIAL_MODE);
gma_write16(sky2->hw, sky2->port, GM_SERIAL_MODE, reg);
gma_write16(hw, port, GM_SERIAL_MODE, reg);