Re: [Qemu-devel] Disabling IRQ error

[Xie Xianshan <xiexs@cn.fujitsu.com>]

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

Thanks,
Simen

于 2013/09/11 17:29, Max Filippov 写道:
> On Wed, Sep 11, 2013 at 12:12 PM, Xie Xianshan<xiexs@cn.fujitsu.com>  wrote:
>>    I want to add a new device "fpga" for e500, and trigger an interrupt IRQ3
>> while the register BB_INTR_REG which belongs to device "fpga" is wrote by
>> the device driver of "fpga".
>>    For e500, IRQ3 is an external interrupt irq.
>>    According the debug log, the disabling error is encoutered during writing
>> BB_INTR_REG register.
>>    - write BB_INTR_REG register
>>        - qemu_irq_raise() 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_write(FPGAState *s, unsigned int offset, uint32_t value,
>> unsigned size) {
>>      switch(offset) {
>>      case BB_INTR_REG:
>>          qemu_irq_raise(s->irq);
>>          break;
>         case BB_INTC_REG:
>             qemu_irq_lower(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
>
>
>