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Date: Wed, 23 Oct 2013 10:38:11 +0800
From: Xie Xianshan <xiexs@cn.fujitsu.com>
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Subject: Re: [Qemu-devel] Disabling IRQ error
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To: qemu-devel@nongnu.org, Max Filippov <jcmvbkbc@gmail.com>

Dear Max,
     Sorry for the late reply.
     Thanks for your advice about lowering the irqs after raising them,=20
and that fixed my problem.
     Thanks again for your kindness.

Thanks,
Simen

=E4=BA=8E 2013/09/11 17:29, Max Filippov =E5=86=99=E9=81=93:
> On Wed, Sep 11, 2013 at 12:12 PM, Xie Xianshan<xiexs@cn.fujitsu.com>  wro=
te:
>>    I want to add a new device "fpga" for e500, and trigger an interrupt =
IRQ3
>> while the register BB=5FINTR=5FREG which belongs to device "fpga" is wro=
te by
>> the device driver of "fpga".
>>    For e500, IRQ3 is an external interrupt irq.
>>    According the debug log, the disabling error is encoutered during wri=
ting
>> BB=5FINTR=5FREG register.
>>    - write BB=5FINTR=5FREG register
>>        - qemu=5Firq=5Fraise() is called.
>>        - after serval minutes,
>>          the error message about disabling irq is displayed.
>>    - continue the next execution without error(with poll?)
>
> So your device raises IRQ, but it doesn't lower it. Real devices
> usually don't do that, they either generate a short pulse on the
> IRQ line (in case of edge-triggered IRQ) or raise IRQ line on
> some event and then lower it on a command from its driver
> (level-triggered IRQ).
>
> You can do the following to make your device behave that way:
> - make your fpga device capable of lowering its IRQ, e.g. by adding
>    another register:
>
>> static void fpga=5Fwrite(FPGAState *s, unsigned int offset, uint32=5Ft v=
alue,
>> unsigned size) {
>>      switch(offset) {
>>      case BB=5FINTR=5FREG:
>>          qemu=5Firq=5Fraise(s->irq);
>>          break;
>         case BB=5FINTC=5FREG:
>             qemu=5Firq=5Flower(s->irq);
>             break;
>>      }
>> }
>
> - provide an interrupt service routine in the linux driver for your fpga
>    device that would check whether the interrupt was caused by its
>    device, and if so lower the device's IRQ.
>
> Thanks.
> -- Max
>
>
>


=