void isr(void)
{
    __attribute__((unused)) unsigned int irqs;

    irqs = irq_pending() & irq_getmask();
#ifdef CSR_UART_BASE
#ifndef UART_POLLING
    if(irqs & (1 << UART_INTERRUPT))
        uart_isr();
    else
        printf("irq: %i\n", irqs);
#endif
#endif
}