Re: [RFC PATCH 2/2] serial: 8250_dw: support polling mode

[John Garry]

On 23/02/2018 17:35, Andy Shevchenko wrote:
> On Fri, 2018-02-23 at 02:42 +0800, John Garry wrote:
> > It would be useful to make this driver support some
> > 8250-compatible devices which have no interrupt line.
> >
> > For these, we allow for no interrupt, and will fallback on
> > polling mode.
> >
> > Note: the 8250 dt bindings state that "interrupts"
> > is a required property:
> > "interrupts : should contain uart interrupt."
> >
> > But the 8250_of.c driver can live without it. So
> > this patch is going this way also.
>
> It should be documented in the binding.

Agreed. I find the wording a bit ambigious in bindings/serial/8250.txt 
and snps-dw-apb-uart.txt:

Required properties:
[...]
- interrupts : should contain uart interrupt.

It uses the word "should", and not "must". Maybe "should" means "must"...

> >  	if (irq < 0) {
> > -		if (irq != -EPROBE_DEFER)
> > -			dev_err(dev, "cannot get irq\n");
> > -		return irq;
> > +		if (irq == -EPROBE_DEFER)
> > +			return irq;
> > +		dev_warn(dev, "cannot get irq, using polling
> > mode\n");
> > +		irq = 0;
>
> NO_IRQ _is_ 0. You need to do something like
>
> if (irq < 0) }
>  ... leave existing code ...
> }
>
> if (!irq)
>  dev_warn(, "Use polling mode\n");

OK

>

Thanks,
John