On 10/05/16 13:12, Felipe Balbi wrote:
>
> Hi,
>
> Roger Quadros <rogerq@xxxxxx> writes:
>>>> @@ -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.
>>
>> But in this case we don't need a bottom half as there is nothing to do :).
>>
>>>
>>> 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.
>>>
>>
>> Why do this at all if there is nothing to do in the bottom half?
>
> oh, but there is :-)
>
> The whole idea of threaded IRQs is that you spend as little time as
> possible on top half and the (strong) recommendation is that you *only*
> check if $this device generated the interrupt. Note that "checking if
> $this device generated the interrupt" will be mandatory as soon as you
> mark the IRQ line as shared ;-)
>
> So here's how this should look like:
>
> static irqreturn_t dwc3_omap_interrupt(int irq, void *_omap)
> {
> struct dwc3_omap *omap = _omap;
> u32 reg;
>
> reg = readl(IRQSTATUS)
> if (reg) {
> mask_interrupts(omap);
> return IRQ_WAKE_THREAD;
> }
>
> return IRQ_HANDLED;
> }
>
> static irqreturn_t dwc3_omap_threaded_interrupt(int irq, void *_omap)
> {
> struct dwc3_omap *omap = _omap;
> u32 reg;
>
> spin_lock(&omap->lock);
> reg = readl(IRQSTATUS);
>
> if (reg & BIT0)
> handle_bit_0(omap);
>
> if (reg & BIT1)
> handle_bit_1(omap);
>
> unmask_interrupts(omap);
> spin_unlock(&omap->lock);
>
> return IRQ_HANDLED;
> }
>
> this will *always* behave well with RT and non-RT kernels. It also
> allows for the user to change priorities on these interrupt handlers if
> necessary.
>
No problem, I can implement a bottom half. We are not handling anything
there at the moment so it is a bit of an overkill :)
It might help in the future if someone wants to handle something.
cheers,
-roge
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