at91usart_readreg
csr = at91usart_readreg(sc, US_CSR);
imr = at91usart_readreg(sc, US_IMR);
csr = at91usart_readreg(sc, US_CSR);
DPRINTFN(5, ("%s: %s, ier=%08x (csr=%08x)\n", device_xname(sc->sc_dev), __FUNCTION__, sc->sc_ier, at91usart_readreg(sc, US_CSR)));
(void)at91usart_readreg(sc, US_CSR); \