Taking tiling and rotation into account in watermark computations

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

Hi all,

We need to refactor the current code a bit to allow parameters like 
plane rotation and framebuffer tiling mode be taken into account when 
calculating display watermarks.

I looked into this code a bit and am at the moment a bit confused with 
what is where and why.

For example the purpose of plane_config in intel_crtc seems a bit thin, 
or why it is created once on driver init. Then again watermark 
parameters are embedded in intel_plane, which is separate from 
plane_config. And where is the link between intel_crtc and intel_plane, 
or why intel_crtc has a plane field - is it not that there are multiple 
planes per pipe/crtc?

Part one would be trying to understand how things are. Then part two 
would be coming up with a design, if justified by the extent of work 
required, to implement this requirement.

Thanks,

Tvrtko