[Qemu-devel] Re: [PATCH] sparc32 esp fix spurious interrupts in chip reset

[Artyom Tarasenko <atar4qemu@googlemail.com>]

2010/6/1 Blue Swirl <blauwirbel@gmail.com>:
> On Tue, Jun 1, 2010 at 7:56 PM, Artyom Tarasenko
> <atar4qemu@googlemail.com> wrote:
>> 2010/6/1 Blue Swirl <blauwirbel@gmail.com>:
>>> On Sun, May 30, 2010 at 10:35 PM, Artyom Tarasenko
>>> <atar4qemu@googlemail.com> wrote:
>>>> lower interrupt during chip reset. Otherwise the ESP_RSTAT register
>>>> may get out of sync with the IRQ line status. This effect became
>>>> visible after commit 65899fe3
>>>
>>> Hard reset handlers should not touch qemu_irqs, because on cold start,
>>> the receiving end may be unprepared to handle the signal.
>>
>> Wouldn't the real hardware lower irq on the hardware reset?
>
> Yes, but since qemu_irqs have no state, and on a cold start or system
> reset all other devices are guaranteed to be reset, the callback would
> be useless.
>
>> And if it would not, would it still clear the corresponding bit in
>> the ESP_RSTAT register?
>
> All registers are set to zero in the lines below.
>
>>
>>> See
>>> 0d0a7e69e853639b123798877e019c3c7ee6634a,
>>> bc26e55a6615dc594be425d293db40d5cdcdb84b and
>>> 42f1ced228c9b616cfa2b69846025271618e4ef5.
>>>
>>> For ESP there are two other sources of reset: signal from DMA and chip
>>> reset command. On those cases, lowering IRQ makes sense.
>>>
>>> So the correct fix is to refactor the reset handling a bit. Does this
>>> patch also fix your test case?
>>
>> It does, but
>>
>> +static void esp_soft_reset(DeviceState *d)
>> +{
>> +    ESPState *s = container_of(d, ESPState, busdev.qdev);
>> +
>> +    qemu_irq_lower(s->irq);
>>
>> Shouldn't it be esp_lower_irq(s)? What's going to happen to the
>> DMA_INTR bit if dma was the source of the irq?
>
> Again, the registers are zeroed in esp_hard_reset().

How does it zero the _DMA_ registers? And sparc32_dma does share the
IRQ line with ESP, doesn't it?

>
> Thanks for testing.
>



-- 
Regards,
Artyom Tarasenko

solaris/sparc under qemu blog: http://tyom.blogspot.com/