[U-Boot] [PATCH 2/6] serial: add UniPhier serial driver

Masahiro Yamada
2014-07-10T11:31:01Z

Hi Marek,

On Thu, 10 Jul 2014 12:14:35 +0200
Marek Vasut <marex@denx.de> wrote:

>
> > > > +static void uniphier_serial_putc(struct uniphier_serial *port, const
> > > > char c) +{
> > > > + if (c == '\n')
> > > > + uniphier_serial_putc(port, '\r');
> > > > +
> > > > + while (!(readb(&port->lsr) & UART_LSR_THRE))
> > > > + ;
> > >
> > > I think in this function, you can avoid such completely unbounded loop.
> > >
> > > [...]
> >
> > Why?
> > Could you give me more detailed explanation?
>
> In case the LSR_THRE bit would never get cleared, this loop would keep spinning
> forever. On the other hand, if there was some kind of a timeout, U-Boot would be
> able to continue doing at least something when exiting this loop by timing out.
> Though you're right that something would most likely have gone really bonkers if
> this LSR_THRE never got cleared.
>

I guess you mentioned the case where the flow control with CTS/RTS
results in the dead lock.

I am not sure if we need to be so careful.

Is there any other UART driver using timeout check?

(What would U-Boot continue to do in case console cannot display the error message?)

Best Regards
Masahiro Masahiro