[Intel-gfx] [PATCH 15/25] drm/i915/fbc: rewrite the multiple_pipes_ok() code for locking

[Maarten Lankhorst]

Op 19-01-16 om 14:35 schreef Paulo Zanoni:
> Older FBC platforms have this restriction where FBC can't be enabled
> if multiple pipes are enabled. In the current code, we disable FBC
> before the second pipe becomes visible.
>
> One of the problems with this code is that the current
> multiple_pipes_ok() implementation just iterates through all CRTCs
> looking at their states, but it doesn't make sure that the state
> locks are grabbed. It also can't just grab the locks for every CRTC
> since this would kill one of the biggest advantages of atomic
> modesetting.
>
> After the recent FBC changes, we now have the appropriate locks for
> the given CRTC, so we can just try to maintain the state of each CRTC
> and update it once intel_fbc_pre_update is called.
>
> As a last note, I don't have gen 2/3 machines to test this code. My
> current plan is to enable FBC on just the newer platforms, so this
> patch is just an attempt to get the gen 2/3 code at least looking
> sane, so if one day someone decide to fix FBC on these platforms, they
> may have less work to do.
>
It would still be nice if pre/post update took a crtc_state and plane_state so we wouldn't have to worry about lifetime issues.
Right now it's pulled from various places.

~Maarten