RE: [PATCH v9 5/6] usb:cdns3 Add Cadence USB3 DRD Driver

From: Felipe Balbi
Date: Tue Jul 09 2019 - 03:22:47 EST



Hi,

Pawel Laszczak <pawell@xxxxxxxxxxx> writes:
>>>>> IRQF_ONESHOT can be used only in threaded handled.
>>>>> "
>>>>> * IRQF_ONESHOT - Interrupt is not reenabled after the hardirq handler finished.
>>>>> * Used by threaded interrupts which need to keep the
>>>>> * irq line disabled until the threaded handler has been run.
>>>>> "
>>>>
>>>>so?
>>>
>>> I don't understand why If I don't have threaded handler why I need IRQF_ONESHOT.
>>> Why interrupt cannot be reenabled after hardirq handler finished ?
>>> I do not use threaded handler so this flag seem unnecessary.
>>
>>Unless this has changed over the years, it was a requirement from IRQ susbystem.
>>
>> /*
>> * Drivers are often written to work w/o knowledge about the
>> * underlying irq chip implementation, so a request for a
>> * threaded irq without a primary hard irq context handler
>> * requires the ONESHOT flag to be set. Some irq chips like
>> * MSI based interrupts are per se one shot safe. Check the
>> * chip flags, so we can avoid the unmask dance at the end of
>> * the threaded handler for those.
>> */
>> if (desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)
>> new->flags &= ~IRQF_ONESHOT;
>
> From description I understand that it should be set when driver uses only
> threaded handler without hard irq handler.
> eg.
>
> ret = devm_request_threaded_irq(dev, data->usb_id_irq,
> NULL, int3496_thread_isr,
> IRQF_SHARED | IRQF_ONESHOT |
> IRQF_TRIGGER_RISING |
> IRQF_TRIGGER_FALLING,
> dev_name(dev), data);
>
> It make sense, we don't have hard irq handler so we can't clear source of interrupt.
> If we clear it immediately in interrupt controller then the same interrupt could
> be raised again, because it was not cleared e.g in controller register.

You are correct. Big mistake on my side. Apologies.

--
balbi