[Intel-gfx] [PATCH 0/2] drm/i915: Gen2 vblank stuff

[ville.syrjala at linux.intel.com]

Continuing a bit with improving the vblank timestamp stuff, I decided that
it's also time to fix gen2 properly.

All this time we've been pretending it has the same pixel+frame counter that
gen3 and gen4 have, when in fact it doesn't. Luckily the same offset has
nothing else on gen2, so it has just read out as 0 and everything more or
less worked.

Sadly there doesn't seem to be any frame counter register on gen2. For the
scanout position, DSL + additional tricks works equally well for gen2 as
it does for ctg+.

This series should be applied on top of my earlier vblank/scanout position
improvements.