Try to minimize the used hw cursor size in order to
minimize power consumption. There is no kernel query
for the minimum so we'll just probe around with
setcursor2 (using an invisible cursor image so
there will be no visual artifacts).
To avoid having to deal with absolutely every size stick
to power-of-two numbers. And with a bit of extra effort
we can determine whether non-square dimesions will also
work, which they do to some degree on current Intel GPUs.
On my Alderlake laptop I'm seeing a massive (up to .5W)
difference in power consumption between 64x64 vs. 256x256
cursors. While some of that is undoubtedly something that
needs to be fixed in i915's display data buffer allocation
code, it still makes sense to use as small as possible
cursor to minimize the wastege.
In case the crtc is rotated just punt to the max cursor size
for now since midlayer has already done the coordinate
transformations based on that. To make smaller cursors work
with rotation we'd either need to make the midlayer(s) aware
of the final cursor size, or just handle the whole roation
business in modesetting. I suspect the latter option would
be easier.
v2: Only allow square cursors in most cases for now as eg.
on modern Intel hardware non-square only works with
wide+short but not with narrow+tall cursors. Non-square
size may still be used when maximum limits aren't
square and the squared+POT'd dimensions would exceed
one of the max limits.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
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