Re: G5 powermacs

[Michael <macallan%netbsd.org@localhost>]

Hello,

On Fri, 09 Jun 2017 15:35:54 +0200 (CEST)
Havard Eidnes <he%NetBSD.org@localhost> wrote:

> > I see the "OF_Quiesce finished" printout and the first few lines
> > of the kernel messages, but once it has printed the line which
> > starts with "genfb0", the screen blanks for me and (apparently)
> > never unblanks.  I should perhaps note that the G5 I use has
> > nvidia graphics.  Hmm, what happens if I comment out "genfb" from
> > the kernel config? (It'll probably bomb later when it finds it
> > has no wsdisplay?)  
> 
> "Not exactly."  What did happen was however that after the
> "OF_QUIESCE finished" message was that no output was printed on
> the screen.
> 
> So ... what's the magic to make this machine not turn off video
> after genfb0 is probed?

Huh, this is weird genfb can't really turn off the video, it's got no
knowledge of the hardware beyond scribbling into the framebuffer.
So:
- did it actually turn the screen off or just draw everything in black?
- did it crash or continue booting?

I dimly remember a firmware bug I encountered with a geforce 2mx
( which ultimately prompted me to write gffb ) - OpenFirmware's color!
method would not work properly, and only write colour registers for one
output, not necessarily the one you plugged your monitor in ( IIRC it
only worked for the analog output, not the DVI one ). Genfb depends on
firmware commands like this to access palette registers. If this
doesn't work it may end up with a mostly black palette.

Some things to try:
- plug the monitor into the other port, see if that helps
- in genfb.c, comment out the RI_8BIT_IS_RGB and RI_ENABLE_ALPHA flags.
  This will prompt genfb to setup a traditional 16 colour ANSI palette
  instead of an R3G3B2 one suitable for anti-aliased fonts. The colours
  may look wrong ( since we inherit whatever OF set up ), but should be
  readable.

> > A few tens of seconds later, the fans in the machine appear to
> > spin up to full speed.  Since the screen is still blank, I have
> > at this point no way to interact with the system, so I had to
> > turn it off again with a long press on the power button.  
> 
> This behaviour continued, of course.

That's the SMU thinking we crashed, which we may or may not have. The
OF_Quiesce command mentioned above is supposed to tell it that the
operating system is up and running, but never worked for me either. No
idea why.

have fun
Michael