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

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

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.

>  	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");

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy