[Intel-gfx] scaling on ivy bridge

[ron minnich]

I have a display that is, e.g., 2560x1600 on an ivybridge. I'd like to
set it up so that the software sees a display with half that
resolution, i.e. the software that draws into the frame buffer (this
is a bios) can draw into what it sees as a 1280x800 display.

I've tried a few things but I'm realizing I don't understand the
ivybridge panel fitter at all. This display is on PIPEA. It appears on
sandybridge one can write
PFA_VSCALE, PFA_HSCALE, PFA_WIN_SZ, and PFA_WIN_POS and _PFA_CTL_1 and
it all works.

On Ivybridge it seems far more complex. Or am I missing something? I
don't see any fitting code in the drm driver itself, so I'm not quite
sure how it's done.

Thanks in advance, as always.

ron