Re: [PATCH-for-8.2 v4 09/10] hw/char/pl011: Add transmit FIFO to PL011State

[Juan Quintela <quintela@redhat.com>]

Richard Henderson <richard.henderson@linaro.org> wrote:
> On 11/9/23 11:28, Philippe Mathieu-Daudé wrote:
>> @@ -436,6 +438,24 @@ static const VMStateDescription vmstate_pl011_clock = {
>>       }
>>   };
>>   +static bool pl011_xmit_fifo_state_needed(void *opaque)
>> +{
>> +    PL011State* s = opaque;
>> +
>> +    return !fifo8_is_empty(&s->xmit_fifo);
>> +}
>> +
>> +static const VMStateDescription vmstate_pl011_xmit_fifo = {
>> +    .name = "pl011/xmit_fifo",
>> +    .version_id = 1,
>> +    .minimum_version_id = 1,
>> +    .needed = pl011_xmit_fifo_state_needed,
>> +    .fields = (VMStateField[]) {
>> +        VMSTATE_FIFO8(xmit_fifo, PL011State),
>> +        VMSTATE_END_OF_LIST()
>> +    }
>> +};
>> +
>>   static int pl011_post_load(void *opaque, int version_id)
>>   {
>>       PL011State* s = opaque;
>> @@ -487,7 +507,11 @@ static const VMStateDescription vmstate_pl011 = {
>>       .subsections = (const VMStateDescription * []) {
>>           &vmstate_pl011_clock,
>>           NULL
>> -    }
>> +    },
>> +    .subsections = (const VMStateDescription * []) {
>> +        &vmstate_pl011_xmit_fifo,
>> +        NULL
>> +    },
>>   };
>
> It just occurred to me that you may need a vmstate_pl011 pre_load() to
> empty the FIFO, which will then be filled if and only if the saved
> vmstate_pl011_xmit_fifo subsection is present.
>
> Juan, have I got this correct about how migration would or should handle a missing subsection?

I hav'nt looked about how the device is created. But if it is created
with the fifo empty you don't need the pre_load().

I have no idea about this device, but sometimes it just happens that if
the fifo has data, you need to put an irq somewhere or mark it some
place that there is pending job on this device.

Later, Juan.