Re: [PATCH 06/15] drm/panfrost: Fix implicit sync

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Jun 23, 2021 at 06:47:37PM +0200, Boris Brezillon wrote:
> On Tue, 22 Jun 2021 18:55:02 +0200
> Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> 
> > Currently this has no practial relevance I think because there's not
> > many who can pull off a setup with panfrost and another gpu in the
> > same system. But the rules are that if you're setting an exclusive
> > fence, indicating a gpu write access in the implicit fencing system,
> > then you need to wait for all fences, not just the previous exclusive
> > fence.
> > 
> > panfrost against itself has no problem, because it always sets the
> > exclusive fence (but that's probably something that will need to be
> > fixed for vulkan and/or multi-engine gpus, or you'll suffer badly).
> > Also no problem with that against display.
> > 
> > With the prep work done to switch over to the dependency helpers this
> > is now a oneliner.
> > 
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Rob Herring <robh@kernel.org>
> > Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
> > Cc: Steven Price <steven.price@arm.com>
> > Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
> > Cc: Sumit Semwal <sumit.semwal@linaro.org>
> 
> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

Pushed the 3 panfrost patches to drm-misc-next, thanks for reviewing them.
-Daniel

> 
> > Cc: "Christian König" <christian.koenig@amd.com>
> > Cc: linux-media@vger.kernel.org
> > Cc: linaro-mm-sig@lists.linaro.org
> > ---
> >  drivers/gpu/drm/panfrost/panfrost_job.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> > index 71cd43fa1b36..ef004d587dc4 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> > +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> > @@ -203,9 +203,8 @@ static int panfrost_acquire_object_fences(struct drm_gem_object **bos,
> >  	int i, ret;
> >  
> >  	for (i = 0; i < bo_count; i++) {
> > -		struct dma_fence *fence = dma_resv_get_excl_unlocked(bos[i]->resv);
> > -
> > -		ret = drm_gem_fence_array_add(deps, fence);
> > +		/* panfrost always uses write mode in its current uapi */
> > +		ret = drm_gem_fence_array_add_implicit(deps, bos[i], true);
> >  		if (ret)
> >  			return ret;
> >  	}
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch