TXCSR4
reg = rt2x00mmio_register_read(rt2x00dev, TXCSR4);
rt2x00mmio_register_write(rt2x00dev, TXCSR4, reg);
reg = rt2x00mmio_register_read(rt2x00dev, TXCSR4);
rt2x00mmio_register_write(rt2x00dev, TXCSR4, reg);