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

[Rob Clark]

On Wed, Feb 4, 2015 at 12:23 PM, Boris Brezillon
<boris.brezillon at free-electrons.com> wrote:
> 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 just wrap drm_atomic_helper_commit() w/ your own fxn that did
extra fixup and then called drm_atomic_helper_commit()?

BR,
-R

> 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