prom_putchar_wait
prom_putchar_wait(base + UART_LSR * 4, UART_LSR_BOTH_EMPTY);
prom_putchar_wait(base + UART_LSR * 4, UART_LSR_BOTH_EMPTY);
prom_putchar_wait(base + AR933X_UART_DATA_REG, AR933X_UART_DATA_TX_CSR);
prom_putchar_wait(base + AR933X_UART_DATA_REG, AR933X_UART_DATA_TX_CSR);