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

[Masahiro Yamada]

Hi Marek,



On Thu, 10 Jul 2014 12:14:35 +0200
Marek Vasut <marex at 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