[PATCH 1/3] irqchip: sun4i: Don't mask + unmask for the non oneshot case

Hans de Goede
2014-03-14T18:42:00Z

Hi,

On 03/14/2014 12:35 PM, Thomas Gleixner wrote:
> On Thu, 13 Mar 2014, Hans de Goede wrote:
>
>> Since sun4i and sun5i are single core SOCs there is no need to mask non
>> oneshot IRQs, to achieve this we use handle_fasteoi_irq with a dummy eoi.
>
> This is slightly wrong :)
>
> Even on a SMP system there is no need to mask the interrupt when the
> controller works like that sunxi one. If the controller is not broken
> beyond repair then it does not deliver the same interrupt to a
> different cpu. Such a thing would always deliver it to all cores and
> those would race to grab the spinlock and mask it. I've seen such
> horror, but don't ask how that performs.
>
> The reason why you can spare the mask/unmask dance is that the
> controller does not require any action and clears the interrupt when
> the level goes back to inactive. That happens when the device handler
> acks it at the device level.
>
> Now there might be the case when the device reactivates the interrupt
> before the RETI. But that does not matter as we run the primary
> interrupt handlers with interrupts disabled.

Ok, I'm going to wait a bit to see if Maxime has anything to say
to this second series, and then I'll do a v2 with the commit msg
fixed.

Regards,

Hans

>
> Thanks,
>
> tglx
>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>> drivers/irqchip/irq-sun4i.c | 11 ++++++++++-
>> 1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/irqchip/irq-sun4i.c b/drivers/irqchip/irq-sun4i.c
>> index a0ed1ea..0a71990 100644
>> --- a/drivers/irqchip/irq-sun4i.c
>> +++ b/drivers/irqchip/irq-sun4i.c
>> @@ -74,8 +74,17 @@ static void sun4i_irq_unmask(struct irq_data *irqd)
>> sun4i_irq_base + SUN4I_IRQ_ENABLE_REG(reg));
>> }
>>
>> +/*
>> + * Since sun4i and sun5i are single core SOCs there is no need to mask non
>> + * oneshot IRQs, to achieve this we use handle_fasteoi_irq with a dummy eoi.
>> + */
>> +static void sun4i_irq_dummy_eoi(struct irq_data *irqd)
>> +{
>> +}
>> +
>> static struct irq_chip sun4i_irq_chip = {
>> .name = "sun4i_irq",
>> + .irq_eoi = sun4i_irq_dummy_eoi,
>> .irq_mask = sun4i_irq_mask,
>> .irq_unmask = sun4i_irq_unmask,
>> };
>> @@ -97,7 +106,7 @@ static int sun4i_irq_map(struct irq_domain *d, unsigned int virq,
>> handle_fasteoi_irq);
>> else
>> irq_set_chip_and_handler(virq, &sun4i_irq_chip,
>> - handle_level_irq);
>> + handle_fasteoi_irq);
>>
>> set_irq_flags(virq, IRQF_VALID | IRQF_PROBE);
>>
>> --
>> 1.9.0
>>
>>