Re: [Qemu-ppc] R: Booting Lubuntu 16.04 on qemu-system-ppc produces errors

[BALATON Zoltan]

Hello,

On Tue, 30 Jul 2019, luigi burdo wrote:
> the issue on the color on Linux PPC with ati/radeon/amd was present from 3.x 
> kernel.
> the only way for have right colors on real hardware is the use of the 
> fbdev with 8/16 bit colors or use a real X86 gpu on another pcie slot as 
> second gpu, plus there are many issue with linux and colors (mesa too) 
> on powerpc with X86 gpu too .

There might be multiple problems with Linux drivers so it's hard to test 
emulation with them. I need known working image to know that what I see is 
not caused by driver bugs but insufficient emulation. With all those 
problems also present on real hardware this is not easy to know without 
real hardware to try it.

> Ubuntu MATE 15.10 amdgpu driver on PowerMac G5 with RadeonHD 4650
> the last opensource X11 video driver for X11 amdgpu is start working on quad g5

I'm not sure this is relevant here because amdgpu driver is too new for 
the emulated ati-vga. We're talking about r128 and radeon drivers here 
which may have their own bugs but those are all that may be working with 
ati-vga. The amdgpu driver is for newer cards that are different 
architecture so not emulated and not planned in this emulation so it's 
not really relevant if that works or not on real hardware.

> On Tue, 30 Jul 2019, BALATON Zoltan wrote:
> This patch: http://patchwork.ozlabs.org/patch/1138749/
> should fix inverted colors at least with X FB driver. Tested with some
> images from here:
> https://wiki.qemu.org/Documentation/Platforms/PowerPC#Links

This patch at least fixes colors in 16 bit mode and works with the 
yellowdog an OpenSUSE images from above page while still working with 
MorphOS that uses little endian FB for Rage128P. Problem is that there are 
too many ways to set these cards up and not all of them are emulated and 
maybe some Linux drivers also get it wrong. I could not get r128 driver 
work with recent Xorg and the rage128fb driver in 5.1 kernel seems to not 
set FB big endian yet draw in it like that so only 8bpp works but that may 
be a driver bug and not emulation bug.

The Fedora image tries to use CCE (even on R128P like most rv100 drivers 
also do) so those are not working yet. This may be the next to implement 
to get more things working. But I don't know how it works on real card so 
first have to find out unless someone can tell. What I know is CCE 
microengine should read packets from memory and turn them into register 
accesses but its microcode and working is undocumented. We could look at 
what other emulators do unless someone knows better. Then we have to find 
out how to fit this in QEMU. Is anyone interested in doing that?

Regards,
BALATON Zoltan