On Thu, 31 Mar 2022 at 22:46, Daniel Vetter <daniel.vetter@xxxxxxxx> wrote: > > There's only one exclusive slot, and we must not break the ordering. > Adding a new exclusive fence drops all previous fences from the > dma_resv. To avoid violating the signalling order we err on the side of > over-synchronizing by waiting for the existing fences, even if > userspace asked us to ignore them. > > A better fix would be to us a dma_fence_chain or _array like e.g. > amdgpu now uses, but it probably makes sense to lift this into > dma-resv.c code as a proper concept, so that drivers don't have to > hack up their own solution each on their own. Hence go with the simple > fix for now. > > Another option is the fence import ioctl from Jason: > > https://lore.kernel.org/dri-devel/20210610210925.642582-7-jason@xxxxxxxxxxxxxx/ > > v2: Improve commit message per Lucas' suggestion. > > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx> > Cc: Russell King <linux+etnaviv@xxxxxxxxxxxxxxx> > Cc: Christian Gmeiner <christian.gmeiner@xxxxxxxxx> > Cc: etnaviv@xxxxxxxxxxxxxxxxxxxxx Hm thinking about this some more, with Christian's dma_resv_usage work this shouldn't be needed anymore. Christian, do you want me to drop this? -Daniel > --- > drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c > index 5f502c49aec2..14c5ff155336 100644 > --- a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c > @@ -178,19 +178,21 @@ static int submit_fence_sync(struct etnaviv_gem_submit *submit) > for (i = 0; i < submit->nr_bos; i++) { > struct etnaviv_gem_submit_bo *bo = &submit->bos[i]; > struct dma_resv *robj = bo->obj->base.resv; > + bool write = bo->flags & ETNA_SUBMIT_BO_WRITE; > > - if (!(bo->flags & ETNA_SUBMIT_BO_WRITE)) { > + if (!(write)) { > ret = dma_resv_reserve_shared(robj, 1); > if (ret) > return ret; > } > > - if (submit->flags & ETNA_SUBMIT_NO_IMPLICIT) > + /* exclusive fences must be ordered */ > + if (submit->flags & ETNA_SUBMIT_NO_IMPLICIT && !write) > continue; > > ret = drm_sched_job_add_implicit_dependencies(&submit->sched_job, > &bo->obj->base, > - bo->flags & ETNA_SUBMIT_BO_WRITE); > + write); > if (ret) > return ret; > } > -- > 2.34.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
