Re: [Qemu-ppc] R128 interrupts

[BALATON Zoltan]

On Fri, 9 Aug 2019, Jd Lyons wrote:
> At this point, what we need is correct handling of the interrupts, I’ve 
> looked into how the USB and Network adapters handle interrupts, but it 
> didn’t provide me with any code I could hack into the Rage128 support.

A simple example on how to implement an interrupt on a PCI card might be 
the hw/ide/sii3112.c although it does not raise the interrupts itself as 
that's done in the ide code so maybe there are simpler devices somewhere. 
But I'm not sure if we can implement the interrupt for ati-vga yet.

> It’s going to take a skilled programmer, not a hacker like me.

I think it's more knowledge about ati vga chips (or reading the docs) is 
needed than skills here. Once we know what we need to implement it's 
probably easy the hard part is to gather the info on what should be 
impemented and understand how it should work.

> The next step would be the GA plugin, but we can’t debug that until we 
> get a correctly working interrupt situation.

Someone should check what the interrupt is used for on the ati card. My 
guess without knowing would be that maybe it should raise it for some 
buffers full or empty (in which case we would first need to actually 
implement handling of buffers before we can meaningfully implement 
interrupt) or maybe it could signal end of some operation in which case we 
might be able to implement an interrupt for that as we do all operations 
synchronously at the moment on register writes. (Later this should be made 
async.)

But it might help to make sure it's really is the missing interrupt that 
causes the driver to exit and not missing something else which I'm not 
convinced about yet. It expects an interrupt connected when init-ing and 
exits without that but not sure it would use it that early to switch mode 
and put something in framebuffer but I don't know so we're only guessing. 
If there's anyone here who knows more please share your knowledge.

Regards,
BALATON Zoltan