drm/i915: Fix MSO vs. bigjoiner timings confusion

drm/i915: Fix MSO vs. bigjoiner timings confusion

When calculating pipe_mode and when doing readout we need
to order our steps correctly.

1. We start with adjusted_mode crtc timings being populated
   with the transcoder timings (either via readout or
   compute_config(). These will be per-segment for MSO.
2. For all other uses we want the full crtc timings so
   we ask intel_splitter_adjust_timings() to expand
   the per-segment numbers to their full glory
3. If bigjoiner is used we the divide the full numbers
   down to per-pipe numbers using intel_bigjoiner_adjust_timings()

During readout we also have to reconstruct the adjusted_mode
normal timings (ie. not the crtc_ stuff). These are supposed
to reflect the full timings of the display. So we grab these
between steps 2 and 3.

The "user" mode readout (mainly done for fastboot purposes)
should be whatever mode the user would have used had they
asked us to do a modeset. We want the full timings for this
as the per-segment timings are not suppoesed to be user visible.
Also the user mode normal timings hdisplay/vdisplay need to
match PIPESRC (that is where we get our PIPESRC size
we doing a modeset with a user supplied mode).

And we end up with
- adjusted_mode normal timigns == full timings
- adjusted_mode crtc timings == transcoder timings
  (per-segment timings for MSO, full timings otherwise)
- pipe_mode normal/crtc timings == pipe timings
  (full timings divided by the number of bigjoiner pipes, if any)
- user mode normal timings == full timings with
  hdisplay/vdisplay replaced with PIPESRC size
- user mode crtc timings == full timings

Yes, that is a lot of timings. One day we'll try to remove
some of the ones we don't actually need to keep around...

Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220223131315.18016-10-ville.syrjala@linux.intel.com