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

[Eric Anholt]

Eric Anholt <eric at anholt.net> writes:

> [ Unknown signature status ]
> 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.

Oh, we've got another user of the seqno cb (async flips), anyway, so we
can't delete it quite yet.  I've pushed this patch since it's a clear
improvement (less code, waits for fences from other devices if any).
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