[PATCH] drm/atomic: Add target_vblank support in atomic helpers (v2)

[Grodzovsky, Andrey]

> -----Original Message-----
> From: daniel.vetter at ffwll.ch [mailto:daniel.vetter at ffwll.ch] On Behalf Of
> Daniel Vetter
> Sent: Thursday, January 12, 2017 3:51 AM
> To: Michel Dänzer
> Cc: Grodzovsky, Andrey; Deucher, Alexander; dri-
> devel at lists.freedesktop.org
> Subject: Re: [PATCH] drm/atomic: Add target_vblank support in atomic
> helpers (v2)
> 
> On Thu, Jan 12, 2017 at 9:28 AM, Michel Dänzer <michel at daenzer.net>
> wrote:
> > On 12/01/17 12:48 AM, Grodzovsky, Andrey wrote:
> >>> From: Michel Dänzer [mailto:michel at daenzer.net] On 09/01/17 06:59
> >>> PM, Daniel Vetter wrote:
> >>>> On Fri, Jan 06, 2017 at 03:39:40PM -0500, Andrey Grodzovsky wrote:
> >>>>> Allows usage of the new page_flip_target hook for drivers
> >>>>> implementing the atomic path.
> >>>>> Provides default atomic helper for the new hook.
> >>>>>
> >>>>> v2:
> >>>>> Update code sharing logic between exsiting and the new flip hooks.
> >>>>> Improve kerneldoc.
> >>>>>
> >>>>> Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky at amd.com>
> >>>>
> >>>> Looks all reasonable, I think an ack from Alex that the amd side is
> >>>> in shape too, and I'll pull this into drm-misc.
> >>>
> >>> Andrey, is there an updated patch 2 adapted to current patch 1?
> >>> Other than that and some questionable indentation of parameters in
> >>> function signatures, looks good to me FWIW.
> >>
> >> We are unable to use the atomic helpers both for page_flip and
> >> page_flip_target At their current form mostly due to
> DRM_MODE_PAGE_FLIP_ASYNC flag rejection they do.
> >> I discussed this with Daniel Vetter on IRC and suggested to remove
> >> the rejection but he said the precise semantics of atomic async flip
> >> is not clear yet and it's better to leave that out for now until
> >> there is a  userspace asking for it.
> >> So I tested it by just hacking  the helper to remove the rejection.
> >> Until that settled the original change [PATCH 2/2] drm/amd/dal:
> >> Switch to page_flip_target hook in DAL Is what we plan to use in DAL
> >
> > IIRC Daniel suggested (on IRC?) to use the helper for non-async flips
> > and the current DC code for async flips. Is that feasible?
> 
> We do have some async flip flag reserved for atomic, so we could route it
> through. But since atm there's no one asking for async flips on the atomic
> ioctl I'm a bit wary for fear of ending up with ill-defined semantics. But I guess
> if we do this for legacy pageflips only, and make sure we do still reject async
> flips submitted through the atomic ioctl that should be all fine. And it should
> allow amdgpu to entirely get rid of the legacy flip path, which would be nice.
> 
> Once we have that we could even use it for cursor plane updates (through
> the legacy ioctl, for drivers with universal planes), for those drivers that
> support it.
> -Daniel

So are we ok with a follow-up patch removing the ASYNC_FLIP restriction in the legacy IOCTL
+ adding the drm_mode_crtc_page_flip_target.flags to drm_crtc_state ? In that case as I said before,
at least for DAL we could drop our own page_flip hook and use the avaialbe helpers.

Andrey
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch