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Re: [PATCH v7 6/7] mac_newworld: Deprecate mac99 "via" option


From: BALATON Zoltan
Subject: Re: [PATCH v7 6/7] mac_newworld: Deprecate mac99 "via" option
Date: Fri, 13 Jan 2023 14:32:57 +0100 (CET)

On Fri, 13 Jan 2023, Howard Spoelstra wrote:
On Fri, Jan 13, 2023 at 12:53 AM BALATON Zoltan <balaton@eik.bme.hu> wrote:
The names also show what we intend to
emulate even though the emulation may not be complete or have bugs (this
is also true for other machines in QEMU where a lot of them are not fully
emulated, only well enough to boot guest OSes).


Looks like everybody has forgotten the previous discussion and not read
the docs and deprecation patches where this is explained so I summarise
the proposed change here again:

No, I haven't forgotten that discussion. FWIW (as I cannot contribute): I
personally do not oppose a name change, the new names seem more
descriptive. I tested your patches and they behave as they should. The
functionality does not change. However, my simple point was what's in a
name when the underlying machine does not reflect what the name implies.

In case of powermac3_1 (currently mac99,via=pmu) it does resemble the PowerMac3,1 G4 AGP machine. It's also what the device tree says and the emulated hardware corresponds to that machine, apart from some missing pieces (like I2C) and known bugs in some (like USB) it aims to emulate that machine but it's currently hidden in the obscure via option of mac99 which ny default is some non-existent Mac like machine with cuda. It's much easier for users not having inside knowledge of QEMU to get a machine type which clearly says what it emulates. If we ever want to run firmware ROM from the real machine we also want to make sure we emulate a real machine. I've done some steps in that direction before and submitted RFC patches that could get to an OF prompt with some debugger tweaking and could eventually made to work but it needs Mark's screamer series to get finished and some rewrite of the macio emulation to add I2C cleanly so it's stalled currently but maybe one day we'll get there.

For powermac7,3 it is what qemu-system-ppc64 -M mac99 currently aims to emulate evidenced by the comment at the beginning and that it adds U3 chipset instead of Uninorth but currently only Linux boots on this machine. It may need some more fixes to get other OSes running starting with the device tree. I think the way for that is to move device tree creation to QEMU similar to what other PPC machines do. I have plans for that but it's blocked by not being able to contribute to OpenBIOS as most of my patches are disliked by Mark but I'll keep trying.

The powerboot3,2 is one hardware I could find info on having PMU and ADB and it's the same era as the PowerMac3,1 so has similar hardware but not sure why this combination is even there. What guest needs this that cannot run with either mac99 or powermac3,1?

It is not my place to comment on a possible development agenda. I can only
tell you what I'd like and point out issues.

- qemu-system-ppc -M mac99 is unchanged and works like before it just
warns for the via option and when using it in qemu-system-ppc64 suggesting
using new machines instead so these could evetually be removed next year.
mac99,via=cuda is just mac99 so you can continue to use that, mac99 is
not deprecated and don't want to remove it.

- qemu-system-ppc64 -M mac99 -> powermac7_3

- qemu-system-ppc -M mac99,via=pmu -> powermac3,1

- qemu-system-ppc64 -M mac99,via=pmu-adb -> powerbook3_2

The last one is one of the rare Macs that had adb and pmu, all others with
pmu usually have USB. The PowerMac1,2 (G4 PCI) had CUDA but not with mac99
hardware but more similar to g3beige and no ADB ports according to
https://en.wikipedia.org/wiki/Power_Mac_G4#1st_generation:_Graphite
https://en.wikipedia.org/wiki/Power_Macintosh_G3_(Blue_and_White)#Hardware

The PowerMac7,3 seems to be matching the PCI device listing in the comment
at the beginning of mac_newworld.c and also this article:
https://www.informit.com/articles/article.aspx?p=606582

What is the 2 USB devices problem? Is it the one we've debugged before and
found that it's noted in a comment marked with ??? in hw/usb/hcd-ohci.c?
That could be fixed if there was somebody interested enough to provide a
patch.


It is not about passing through USB devices and active packets per
endpoint. The powermac3,1 has two 2 USB 1.1 ports. However, when booting
Mac OS 9.0.4 with via=pmu it will support only one (the kbd).  When started
with via=cuda -usb -device usb-kbd -device usb-mouse it will support the
first-mentioned usb-kbd. When kbd and mouse arguments are reversed it
supports the other device ;-)

Is this something that happens on real hardware as well or is it some bug in emulation somewhere? If the drivers on this OS keep active packets on different endpoints then it's the same issue we've discovered with USB pass through of audio devices that also need this feature. If it's something else it may be fixable but we need to understand first what causes the issue.

Regards,
BALATON Zoltan



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