Atmel HLCDC + Atomic operations: hook for internal atomic state change

[Boris Brezillon]

Hello,

I'm currently adding support for atomic operations (or atomic
modesetting) in the Atmel HLCDC driver.
Everything is pretty much in place, and all the features provided by the
current driver are working as expected.
However, there's one feature I'd like to add (actually I was hoping
atomic support could help me deal with this feature), and I not sure
how to do it.

The HLCDC IP provides a way to discard a specific area on the primary
plane (in case at least one of the overlay is activated and alpha
blending is disabled).
Doing this will reduce the amount of data to transfer from the main
memory to the Display Controller, and thus alleviate the load on the
memory bus (since this link is quite limited on such hardware,
this kind of optimization is really important).

My problem here is that there is no way, in the current atomic
implementation, to internally ask for a plane state modification.

Is there a plan to add such hooks that would be called after the
requested state modifications (i.e. operations done before the
drm_atomic_commit call in all helper functions), but before the atomic
checks begin (i.e. call to drm_atomic_check_only) ?
Such hooks would let me ask for a primary plane update (modifying the
discard area property) if needed.

Maybe I'm totally mistaken in my approach to solve this problem, so
please let me know if you see other solutions.

Thanks.

Best Regards,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com