[OpenBIOS] [PATCH v4] arch/ppc/qemu: Add a node for the other (empty) PCI bus to the device tree

[BALATON Zoltan]

On Sat, 30 Jun 2018, Mark Cave-Ayland wrote:
> On 29/06/18 21:10, BALATON Zoltan wrote:
>
>>> How about changing ob_pci_init() to take a single bus_num int which is the 
>>> starting bus number and then passing that down into 
>>> ob_configure_pci_device()? That will allow you to set the correct bus_num 
>>> for the 0xf2000000 PCI bus which should solve your problem, and also get 
>>> OpenBIOS a small step closer to multiple PCI bus support.
>> 
>> I don't remember the details by now and don't want to debug this again but 
>> AFAIR the problem was not the bus-range but that only one PCI bus appears 
>> in the device tree while there are two buses emulated. I think MorphOS 
>> checks for up to 3 PCI buses and may not get all info from the device tree 
>> apart from addresses but may have some assumptions for other properties so 
>> it may not be possible to fix it with a device tree that does not look 
>> similar enough to a real Mac. Since only one PCI bus was present in the 
>> device tree, when trying to access config registers of bus 1 MorphOS talked 
>> to bus 0 instead which of course did not work as devices are on bus 1 and 
>> config reg accesses went to bus 0 and got ignored silently because there 
>> were no devices on that bus. The devices were still mmio mapped so some of 
>> them appeared to work when did not need initialisation but symptoms were 
>> failing to setting bus master bit for network card and not finding USB 
>> devices that are results of this mismatch between PCI buses. This is fixed 
>> by adding an empty/dummy pci bus 0 in the device tree which makes MorphOS 
>> notice there are two PCI busses and use the correct one for accessing PCI 
>> registers. So there needs to be two PCI buses in the device tree and since 
>> devices are on the second one the dummy one needs to be _before_ the second 
>> one (this is why I could not patch it from Forth or command line and need 
>> this patch).
>> 
>> If you can come up with any other patch to fix this (you can test with the 
>> MorphOS demo iso) then I'm fine with that but I could not find any other 
>> simple way to make this work without multiple PCI bus support in OpenBIOS 
>> but that's too much work I don't have time for. (Since the first PCI bus is 
>> empty it should not matter too much what info we have about that in device 
>> tree now as nothing should access it really.)
>
> I'm not asking that you implement full multiple PCI bus support for OpenBIOS, 
> just that you try setting bus-range manually to the correct value from a real 
> device tree to see if it makes a difference.

Not sure what would be the correct value and where to change it. If you 
give me a patch I can test it.

> Unfortunately my copy of MorphOS (3.7) in my OpenBIOS test repository never 
> seems to get past the bootloader so I don't have a way to test it myself or 
> know what to look for to know if this has succeeded or not.

It needs the target/ppc/translate.c patch I've sent to the QEMU list 
cc-ing you and the command line options in that patch. I'm not sure 3.7 
will work, I think you'd need at least 3.8 but the most recent one is 3.10 
which I'm using for testing now so maybe you should get a recent one.

Regards,
BALATON Zoltan