linux-kernel - Re: [PATCH 2/2] serial: 8250_dw: fall back to poll if there's no interrupt

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Date:   Thu, 3 Aug 2023 00:56:00 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Jisheng Zhang <jszhang@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        linux-serial@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] serial: 8250_dw: fall back to poll if there's no
 interrupt

On Wed, Aug 02, 2023 at 11:05:45PM +0800, Jisheng Zhang wrote:
> When there's no irq(this can be due to various reasons, for example,
> no irq from HW support, or we just want to use poll solution, and so
> on), falling back to poll is still better than no support at all.

...

>  	irq = platform_get_irq(pdev, 0);

You will still have an error message. Perhaps you need to replace it with

	irq = platform_get_irq_optional(pdev, 0);

> -	if (irq < 0)
> -		return irq;
> +	if (irq < 0) {
> +		if (irq != -ENXIO)
> +			return irq;
> +		/* no interrupt -> fall back to polling */
> +		irq = 0;
> +	}

This can be slightly modified:

	/* no interrupt -> fall back to polling */
	if (irq == -ENXIO)
		irq = 0;
	if (irq < 0)
		return irq;

-- 
With Best Regards,
Andy Shevchenko