Re: [PATCH v7 0/8] Pegasos2 emulation

[BALATON Zoltan <balaton@eik.bme.hu>]

On Tue, 16 Mar 2021, BALATON Zoltan wrote:
> On Tue, 16 Mar 2021, Mark Cave-Ayland wrote:
>> On 16/03/2021 17:25, BALATON Zoltan wrote:
>>> On Tue, 16 Mar 2021, Mark Cave-Ayland wrote:
>>>> On 16/03/2021 13:06, BALATON Zoltan wrote:
>>>>>> The PATCH 1 doesn't seem to be needed to have a working Pegasos 2 
>>>>>> machine, does it?
>>>>> 
>>>>> It is needed (as well as all other patches in the series). Patch 1 is 
>>>>> needed for getting serial output which is the only way to communicate 
>>>>> with the Pegasos2 firmware so it's really hard to boot anything without 
>>>>> it.
>>>> 
>>>> Just having a quick look at patch 1: presumably the issue here is that 
>>>> the Pegasos 2 firmware moves the serial ports to a different address on 
>>>> startup. If you know what that address is, then why not simply change the 
>>>> serial port base address(es) on the SuperIO device from the default?
>>> 
>>> I had that as first version but other guests may expect the serial at the 
>>> default address or set it up differently and we can emulate the device 
>>> more fully this way that works with all guests which is also more like the 
>>> device works. So putting it at a default address would be a step back. I 
>>> can attempt that if this approach cannot be used but so far nobody said 
>>> so.
>> 
>> That would certainly be my first choice, as swapping out the memory regions 
>> within the ISA bus without its knowledge is likely to cause problems (I can 
>> see ioport_id being incorrect for one).
>
> Did you check what's that used for? Unlikely to cause any problems other than 
> displaying initial value of port address instead of current address in device 
> ID but that could be argued about if an ID should change or stay the same as 
> initially. Easily fixable either way.
>
>> Do the guest OSs actually use this feature at all? I don't think I've ever 
>> seen such registers being used within QEMU, OSs tend to simply relocate the 
>> IO space base address using the BAR if required.
>
> The ISA devices don't have io BAR, they are relocatable _within_ ISA IO space 
> by the config registers of the VIA superio chip. But the two guests that 
> currently boot (MorphOS and Linux) don't seems to change default set by the 
> firmware so we can go with the firmware defaults which is less correct than 
> actually emulating what the chip does but whatever. (AmigaOS may also boot 
> but has no gfx driver so can't really check at the moment.)
>
>> If Linux/MorphOS work with a fixed address then that's good enough for now: 
>> the code should look something like this:
>>
>>    dev = qdev_new(TYPE_SUPER_IO);
>>    serial_dev = object_resolve_path_component(OBJECT(dev), "serial0"));
>>    qdev_prop_set_uint32(dev, "iobase", 0x1234);
>>    qdev_realise_and_unref(dev, &error_fatal);
>
> I've sent a v8 dropping patch 1 and setting a default but using the callback

And v9 replacing patch 5 with latest that applies on master that has 
changed while I was sending the previous version...

> ISA superio has for this for that which is a bit cleaner IMO.
>
> Could this turned into a pull request by somebody now?
>
> Regards,
> BALATON Zoltan
>
>