linux-kernel - Re: [PATCH v7 1/5] usb: dwc3: omap: use request_threaded

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Date:	Tue, 10 May 2016 12:58:02 +0300
From:	Felipe Balbi <balbi@...nel.org>
To:	Roger Quadros <rogerq@...com>
Cc:	tony@...mide.com, Joao.Pinto@...opsys.com,
	sergei.shtylyov@...entembedded.com, peter.chen@...escale.com,
	jun.li@...escale.com, grygorii.strashko@...com,
	yoshihiro.shimoda.uh@...esas.com, nsekhar@...com, b-liu@...com,
	linux-usb@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org, Roger Quadros <rogerq@...com>
Subject: Re: [PATCH v7 1/5] usb: dwc3: omap: use request_threaded_irq()


Hi,

Roger Quadros <rogerq@...com> writes:
> We intend to share this interrupt with the OTG driver an to ensure
> that irqflags match for the shared interrupt handlers we use
> request_threaded_irq()
>
> If we don't use request_treaded_irq() then forced threaded irq will
> set IRQF_ONESHOT and this won't match with the OTG IRQ handler's
> IRQ flags.
>
> NOTE: OTG IRQ handler is yet to be added. This is a preparatory step.
>
> Signed-off-by: Roger Quadros <rogerq@...com>
> ---
>  drivers/usb/dwc3/dwc3-omap.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/dwc3/dwc3-omap.c b/drivers/usb/dwc3/dwc3-omap.c
> index 59ea35f..6504e94 100644
> --- a/drivers/usb/dwc3/dwc3-omap.c
> +++ b/drivers/usb/dwc3/dwc3-omap.c
> @@ -272,16 +272,22 @@ static irqreturn_t dwc3_omap_interrupt(int irq, void *_omap)
>  {
>  	struct dwc3_omap	*omap = _omap;
>  	u32			reg;
> +	int			ret = IRQ_NONE;
>  
>  	reg = dwc3_omap_read_irqmisc_status(omap);
>  
> +	if (reg)
> +		ret = IRQ_HANDLED;
> +
>  	dwc3_omap_write_irqmisc_status(omap, reg);
>  
>  	reg = dwc3_omap_read_irq0_status(omap);
> +	if (reg)
> +		ret = IRQ_HANDLED;
>  
>  	dwc3_omap_write_irq0_status(omap, reg);
>  
> -	return IRQ_HANDLED;
> +	return ret;
>  }
>  
>  static void dwc3_omap_enable_irqs(struct dwc3_omap *omap)
> @@ -497,8 +503,8 @@ static int dwc3_omap_probe(struct platform_device *pdev)
>  	/* check the DMA Status */
>  	reg = dwc3_omap_readl(omap->base, USBOTGSS_SYSCONFIG);
>  
> -	ret = devm_request_irq(dev, omap->irq, dwc3_omap_interrupt, 0,
> -			"dwc3-omap", omap);
> +	ret = devm_request_threaded_irq(dev, omap->irq, dwc3_omap_interrupt,
> +					NULL, 0, "dwc3-omap", omap);

if you're using threaded_irq, it's better to have a NULL top half and
valid bottom half.

In fact, since this will be shared, you could do a proper preparation
and on top half check if $this device generated the IRQ and
conditionally schedule the bottom half. Don't forget to mask device's
interrupts from top half so you can run without IRQF_ONESHOT.

-- 
balbi

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