Am 25. Mai 2025 00:03:15 UTC schrieb BALATON Zoltan <bala...@eik.bme.hu>:
>On Sun, 28 Jul 2024, BALATON Zoltan wrote:
>> On Sun, 28 Jul 2024, quan wrote:
>>> I am playing around with the parallel port on the pegasos 2 and I noticed
>>> the following issue:
>>> The parallel port on startup is set to iobase 0x378, then later it gets
>>> remapped to iobase 0x3bc.
>>> When I tried writing to the 0x3bc location with
>>> trace:memory_region_ops_write on, I get logs about writing to the location
>>> 'parallel', so far so good, but the writes don't make it through (it never
>>> calls parallel_ioport_write* functions)
>>>
>>> I traced it through where it calls portio_write, and inside the
>>> portio_write code:
>>> This line always fails for me:
>>> const MemoryRegionPortio *mrp = find_portio(mrpio, addr, size, true);
>>> This is due to the mrpio has the offset of 0x44 (0x3bc-0x378) in the list,
>>> and the 'addr' in the code ranges from (0-15) (address relative to 0x3bc),
>>> so it can never match the parallel io function to execute.
>>>
>>> This seems like a bug to me. I think there is some issue where the
>>> portio_list is not getting updated properly after the remapping to 0x3bc.
>>>
>>> The other devices (Serial, RTC, PM, VGA) responds properly for me, so it is
>>> only the parallel port that has this issue.
>>
>> Is this something that broke recently or can the same be reproduced with
>> QEMU v8.2.0. The relocation of these devices was implemented around commit
>> 35a6380b4ed27f (and the ones before that). Adding Bernhard to cc as well.
>
>This commit also seems to break display with some VGA ROMs as can be
>reproduced with:
>
>qemu-system-ppc -machine pegasos2 -bios pegasos2.rom -serial stdio -vga none
>-device ati-vga,romfile=ati-rage128progl16mb.VBI
>
>where the romfile is something from
>http://vgamuseum.info/index.php/companies/item/111-ati-rage-128-pro for
>example). Until commit 35a6380b4ed27f^ you get picture on emulated VGA but not
>after (although I have no idea what a VGA BIOS has to do with the parallel
>port). Any idea how to fix this?
Here an observation: Executing `info mtree` reveals that the parallel port gets
mapped to 0x3bc - 0x3c3 which overlaps with some vga region (0x3c0 - 0x3cf). So
the commit seems to expose a firmware bug in pegasos2.rom or in its default
configuration. On real hardware both devices might respond such that the bug
might not materialize there like in QEMU, but that's just a guess. Maybe one
could work around that by decreasing the priority of the parallel io ports.
Best regards,
Bernhard
>
>Regards,
>BALATON Zoltan
