[PATCH 3/7] drm/vc4: Mimic drm_atomic_helper_commit() behavior

[Eric Anholt]

Boris Brezillon <boris.brezillon at free-electrons.com> writes:

> On Tue, 06 Jun 2017 13:27:09 -0700
> Eric Anholt <eric at anholt.net> wrote:
>
>> Boris Brezillon <boris.brezillon at free-electrons.com> writes:
>> 
>> > The VC4 KMS driver is implementing its own ->atomic_commit() but there
>> > are a few generic helpers we can use instead of open-coding the logic.
>> >
>> > Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
>> > ---
>> >  drivers/gpu/drm/vc4/vc4_kms.c | 38 ++++++++++++--------------------------
>> >  1 file changed, 12 insertions(+), 26 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
>> > index ad7925a9e0ea..f229abc0991b 100644
>> > --- a/drivers/gpu/drm/vc4/vc4_kms.c
>> > +++ b/drivers/gpu/drm/vc4/vc4_kms.c
>> > @@ -42,6 +42,10 @@ vc4_atomic_complete_commit(struct vc4_commit *c)
>> >  	struct drm_device *dev = state->dev;
>> >  	struct vc4_dev *vc4 = to_vc4_dev(dev);
>> >  
>> > +	drm_atomic_helper_wait_for_fences(dev, state, false);
>> > +
>> > +	drm_atomic_helper_wait_for_dependencies(state);  
>> 
>> With this wait_for_fences() addition and the reservation stuff that
>> landed, I think we can rip out the "seqno cb" in vc4, and just use
>> drm_atomic_helper_commit() and drm_atomic_hepler_commit_tail().  Do you
>> see anything missing, with that?
>
> I can't tell. I haven't dig enough to understand what this seqno cb was
> used for :-), but Daniel was suggesting the same thing. I'll try to
> better understand what seqno cb does and if it's all safe to get rid of
> it and use the standard helpers.

The seqno cb was the thing for stalling the modeset until V3D was done
rendering to the planes.  The wait_for_fences() does the same thing
using generic dmabuf reservations, so the seqno cb isn't needed any
more.
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